metals Article
Structure and Selected Properties of Arc Sprayed Coatings Containing In-Situ Fabricated Fe-Al Intermetallic Phases 2, ˛ Tomasz Chmielewski 1, * , Piotr Siwek 1 , Marcin Chmielewski 2, *, Anna Piatkowska 2 1, Agnieszka Grabias and Dariusz Golanski ´ * 1 2
*
Institute of Manufacturing Technologies, Warsaw University of Technology, 85 Narbutta str., 02-524 Warsaw, Poland;
[email protected] Institute of Electronic Materials Technology, Warsaw University of Technology, 133 Wólczynska ´ str., 01-919 Warsaw, Poland;
[email protected] (A.P.);
[email protected] (A.G.) Correspondence:
[email protected] (T.C.);
[email protected] (M.C.);
[email protected] (D.G.); Tel.: +48-22-849-9797 (T.C.); +48-22-639-5815 (M.C.); +48-22-234-8402 (D.G.)
Received: 26 November 2018; Accepted: 11 December 2018; Published: 13 December 2018
Abstract: The paper presents the results of research on the production by means of arc spraying of composite coatings from the Fe-Al system with participation of in-situ intermetallic phases. The arc spraying process was carried out by simultaneously melting two different electrode wires, aluminum and steel. The aim of the research is to create protective coatings with a composite structure with a significant participation of Fex Aly as an intermetallic phases reinforcement. The synthesis of intermetallic phases takes place during the (in-situ) spraying process. Currently most coatings involving intermetallic phases are manufactured by different thermal spraying methods using coating materials in the form of prefabricated powders containing intermetallic phases. The obtained results showed the local occurrence of intermetallic phases from the Fe-Al system, and the dominant components of the structure have two phases, aluminum solid solutions in iron and iron in aluminum. The participation of intermetallic phases in the coating is relatively low, but its effect on the properties of the coating material is significant. Keywords: arc spraying; coatings; Fe-Al; intermetallic phases
1. Introduction Intermetallic phases from the Fe-Al system are attractive coating materials with characteristic properties, especially in comparison with conventional coating materials. Coatings that involve intermetallic phases are at present created via thermal spraying [1–3] as well as welding via different methods [4–7] out of prefabricated intermetallic phase powders. Reports in literature also describe the processes of in-situ manufacturing of intermetallic phases on a modified surface by the alloying of components [8–13]. Intermetallic phases from the Fe-Al system, thanks to their characteristic properties, are increasingly often used as materials for modifying surfaces whose purpose is to work at high temperatures. They are highly resistant to oxidation, carburizing and sulfation at high temperature (up to 900 ◦ C), have a high resistance to erosion and cavitation abrasion, relatively low density and comparatively lower prices compared to corrosion-resistant and acid-resistant steel, which incorporates expensive elements, such as chromium, nickel, and molybdenum [14–20]. Specific to intermetallic phases is their high electrical resistance at room temperature. The materials owe their peculiar properties to an ordered crystal structure with strong chemical bonds, combined with a dense packing of atoms in space, which results in a reduced diffusion speed and increased resistance to creep, recrystallization and high-temperature corrosion, compared to traditional metal Metals 2018, 8, 1059; doi:10.3390/met8121059
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Metals 2018, 8, x FOR PEER REVIEW Metals 2018, 8, 1059 Metals 2018,main 8, x FOR PEER REVIEW 30]. The issue that makes
2 of 12 2 of 12 2 of 12 brittleness in
the use of Fe-Al coatings more difficult is due to their surrounding temperature and the difficulty of shaping ready-made elements to desired dimensions alloys [21–30]. The that mainmakes issue the that makes the use of Fe-Al coatings difficult due to their 30]. The main issue of Fe-Al more difficultmore is due to theirispoint brittleness in via mechanical machining methodsuse [31–35]. Duecoatings to the large difference in the melting of main brittleness in surrounding temperature and the difficulty of shaping ready-made elements to desired surrounding and the difficulty of it shaping ready-made to with desired dimensions components,temperature as well as long-range ordering, is difficult to obtainelements materials a reproducible dimensions viamachining mechanicalmethods machining methods [31–35]. Duedifference to the large difference in the melting via mechanical [31–35]. Due to the large in the melting point of maina composition and structure. The manufacturing method proposed in this paper of creating point of mainas components, as well as long-range ordering, it obtain is difficult to obtain materials with a components, well as long-range ordering, it is difficult to materials with a reproducible composite with the use of an intermetallic phase from the Fe-Al system may serve as an alternative reproducible composition and structure. The manufacturing method proposed in this paper of creating composition and structure. Thewhich manufacturing method proposed in thismainly paperonofintermetallic creating a to the solutions in use at present, are much more expensive and based a compositewith withthe theuse useofofan anintermetallic intermetallicphase phasefrom fromthe theFe-Al Fe-Alsystem system may may serve serve as as an alternative composite powders, prepared before the application process [36,37]. Analysis of the Fe-Al equilibrium system to the solutions in use at present, which are much more expensive and based mainly on intermetallic (Figure 1) implies that only intermetallic phases Fe3Al and FeAl may serve as a matrix for potential before the application process [36,37]. Analysis of the Fe-Al equilibrium system powders, prepared construction materials. This is due to the interesting use properties and a structure that results from (Figure 1) implies that only intermetallic phases Fe3Al Al and and FeAl FeAl may serve as a matrix for potential the regular, spatially centerd structure A2, thereby fulfilling the von Mises plasticity criterion. construction materials. This This is is due due to to the interesting interesting use use properties properties and a structure that results from the regular, spatially centerd centerd structure structure A2, A2, thereby thereby fulfilling fulfillingthe thevon vonMises Misesplasticity plasticitycriterion. criterion.
Figure 1. Fe-Al equilibrium system and elementary cells of A2, D03 and B2 structures. Figure 1. Fe-Al equilibrium system and elementary cells of A2, D03 and B2 structures.
1. Fe-Al equilibrium system and elementary cells of A2, Spray Figure metallization, one variant of which is arc spraying, is D03 partand of B2 thestructures. thermal-mechanical group of coating manufacturing methods. The coating provided form of two wires. Spray metallization, one variant of which is arc material spraying,is is part of in thethe thermal-mechanical Spray metallization, one variant of which is them arc spraying, is part ofair the thermal-mechanical An electric arc running between the wires makes melt, pressurized atomizes thetwo particles, group of coating manufacturing methods. The coating material is provided in the form of wires. group of coating manufacturing methods. The coating material is provided in the form of two wires. accelerating them to speeds of upthe to 150 m/s and sprays thempressurized on a previously preparedthe base. This is An electric arc running between wires makes them melt, air atomizes particles, An electric arc running process. betweenThe the efficiency wires makes them melt, pressurized air material atomizesbeing the particles, a relatively low-energy of arc spraying depends on the sprayed accelerating them to speeds of up to 150 m/s and sprays them on a previously prepared base. This is a accelerating them to speeds of up tois150 m/s and sprays them on a previously prepared base. This and the source power. The process usually conducted manually or on semi-automatically, gun is is relatively low-energy process. The efficiency of arc spraying depends the material beingthe sprayed aheld relatively low-energy process. The efficiency of arc spraying depends on the material being at the distance of 50–200 mm from the object being coated. Oneor pass-through results inthe asprayed coating and the source power. The process is usually conducted manually semi-automatically, gun is and source The process iscases, usually conducted manually or semi-automatically, thetogun is fromthe 250power. µmofthick. most thickness of the One coatings being sprayed high held at120 theto distance 50–200Inmm from the the object being coated. pass-through results due in a coating held at the distance of 50–200 mm from the object being One pass-through results in a coating internal not In exceed mm [30–33]. The coated. arc the electrically conductive from 120stresses to 250 should µm thick. most0.7 cases, the thickness of between the coatings being sprayed due to wires high from 120 to 250 µm thick. In most cases, the thickness of the coatings being sprayed due to high should burn in the axisnot of exceed the nozzle that[30–33]. suppliesThe thearc pressurized air,electrically so that the pressurized air internal stresses should 0.7 mm between the conductive wires internal stresses should not exceed 0.7 mm [30–33]. The arcofbetween the electrically conductive wires gives the particles a suitably high kinetic energy. A model the process has been presented in Figure should burn in the axis of the nozzle that supplies the pressurized air, so that the pressurized air gives should burn in the axis of the nozzle that supplies the pressurized air, so that the pressurized air 2. particles the a suitably high kinetic energy. A model of the process has been presented in Figure 2. gives the particles a suitably high kinetic energy. A model of the process has been presented in Figure 2.
Figure Figure 2. 2. Model Model of of arc arc spraying. spraying.
Figure 2. Model of arc spraying.
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In the course of implementing the research plan, it was assumed that in the process of arc spraying, while independently melting two wires, a steel wire and an aluminum wire, the thermodynamic conditions favorable for synthesis of intermetallic phases from the Fe-Al system will be created as part of the process. 2. Materials and Methods In the spraying process, two different electrode wires were used that were melted at the same time, an aluminum and a steel wire with a 1.6 mm diameter. The coating was sprayed on plates of non-alloy S235JR steel with the dimensions of 60 mm × 60 mm × 5 mm. Before the coating, samples underwent grit blasting, using steel grit in order to clean and develop the surface. The parameters of the spraying process are presented in Table 1. Table 1. Arc spraying parameters. Parameter
Value, Unit
Arc voltage Current Electrode wires diameter Wire feed Spraying air pressure
34 V 250 A 1.6 mm 2.6 m/min 0.3 MPa
The device used to spray the coatings was the arc system ARC140/S350-CL (Metallisation, Dudley, UK) produced by metallization. System ARC140/S350-CL (Closed Loop) was equipped with an Arc140 gun, power supply with selectable working voltage and a closed current control circuit. The operator has the ability to select the current value regardless of the type of wire used, before beginning work. The construction of the system allows many possibilities of configuring the system in the scope of the placement method and drive method of the wires. In the Arc140 gun there is no driving motor of the wires. The Arc140/S350-CL set has a patented system of synchronized drive transmission (Synchrodrive™) that uses one motor as well as an elastic drive shaft. Such a solution ensures constant rotation speed and power of the pull-push system even for 20 meter-long wires. The large range, elastic drive and a small weight of the pistol ensure convenience and the proper work conditions of the operator. The use of arc spraying with the arc system and spray materials in the form of wires significantly lowered the costs of creating coatings. However, during the spraying process, special attention was given to the process parameters, whose window is very narrow because it is difficult to obtain the conditions of simultaneous melting of different metals as iron and aluminum (in the conditions where the feed of both wires is at the same speed). 3. Results 3.1. Metallographic Analysis The created coating underwent metallographic analysis in order to characterize its microstructure and perform microanalysis and phase analysis in order to confirm the synthesis of intermetallic phases. The properties of the binding of the substrate with the coating were observed. During arc spraying, the connection between the coating and the substrate material is adhesive-mechanic, the accelerated droplets/particles that hit the metal surface deform plastically and take a shape based on the stereometric structure of the substrate. Higher adhesion is facilitated by cleaning the surface of the base, thereby increasing the value of the surfacer fee energy. In the first phase, the analysis was done via optical microscope produced by the Olympus company (Hamburg, Germany), equipped with a camera for digital recording of the image. An observation was conducted of metallographic samples of the Fe-Al coating, under ×100 and ×200 magnification. The coating presented in Figure 3 has a multi-phase structure with heavily deformed flat grains with variable thickness. During the
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analysis via optical microscope, three different phases were observed, with dark areas of inclusions Metals 2018, 8, x FOR PEER REVIEW 4 of 12 Metals 2018, 8, x FOR PEERThe REVIEW 4 of 12 and contaminations. coating is relatively densely packed, with few voids and discontinuities. The layer of the coating relatively is wave-shaped. Theisbinding of the coating to the andtop discontinuities. The topislayer of the rough coatingand is relatively rough and wave-shaped. The binding and discontinuities. The top layer of the coating is relatively rough and is wave-shaped. The binding substrate is “adhesive-mechanic” in nature, without a visible intermediate area. of the coating to the substrate is “adhesive-mechanic” in nature, without a visible intermediate area. of the coating to the substrate is “adhesive-mechanic” in nature, without a visible intermediate area.
(a) (a)
(b) (b)
Figure 3. 3. Microstructure of the arc sprayed Figure sprayed Fe-Al Fe-Alcoating coatingon onaasteel steelsubstrate, substrate,with witha ameasurement measurementofof Figure 3. Microstructure of the arc sprayed Fe-Al coating on a steel substrate, with a measurement of thickness, (a) (a) one one pass-through of spraying, (b) thickness, (b) two two passes. passes. thickness, (a) one pass-through of spraying, (b) two passes.
The Fe-Al coating, arc arc sprayed on the analyzed via scanning Thecomposite, composite,multi-phase multi-phase Fe-Al coating, sprayed onsteel the base steelwas base was analyzed via The composite, multi-phase Fe-Al coating, arc sprayed on the steel base was analyzed via electron Auriga produced by the Zeiss company (Oberkochen, Germany). The coating scanningmicroscope electron microscope Auriga produced by the Zeiss company (Oberkochen, Germany). The scanning electron microscope Auriga produced by the Zeiss company (Oberkochen, Germany). The presented in Figurein4 Figure is non-uniform in phase.inBand-like structurestructure is visible,is with fewwith spherical coating presented 4 is non-uniform phase. Band-like visible, few coating presented in Figure 4 is non-uniform in phase. Band-like structure is visible, with few spherical SEM particles. SEMcreated imageswith created with back-scattered a QBSD back-scattered show contrast, a mass particles. images a QBSD electron electron detectordetector show a mass spherical particles. SEM images created with a QBSD back-scattered electron detector show a mass contrast, whereshades different shades of grayphases indicated with different mass. The phase where different of gray indicated withphases different atomic mass.atomic The phase corresponding contrast, where different shades of gray indicated phases with different atomic mass. The phase corresponding to thehas darkest shade hasthe anlightest Al matrix, the has lightest phase has aaddition, Fe matrix. In addition, to the darkest shade an Al matrix, phase a Fe matrix. In phases with an corresponding to the darkest shade has an Al matrix, the lightest phase has a Fe matrix. In addition, phases with an intermediate shade of grey are present, with a small share by volume, which might intermediate of grey areshade present, withare a small share by avolume, which be intermetallics phases with shade an intermediate of grey present, with small share bymight volume, which might be intermetallics from the Fe-Al system with differingThe stoichiometry. The images of theindicate cross-sections from the Fe-Al system differing stoichiometry. images of the cross-sections that the be intermetallics from with the Fe-Al system with differing stoichiometry. The images of the cross-sections indicateisthat the coating is not uniform throughout its thickness. coating not uniform throughout its thickness. indicate that the coating is not uniform throughout its thickness.
(a) (a)
(b) (b)
Figure 4. Scanning electron microscope (SEM) image of the microstructure of the arc sprayed Fe-Al Figure4.4.Scanning Scanning electron electron microscope microscope (SEM) image Figure image of of the the microstructure microstructureof ofthe thearc arcsprayed sprayedFe-Al Fe-Al coating on a steel substrate, (a) ×100, (b) ×150. coatingon onaasteel steelsubstrate, substrate,(a) (a) × ×100, coating 100, (b) (b) ×150. ×150.
3.2. Microhardness Analysis 3.2. Microhardness Analysis Microhardness analysis was conducted by means of the Leitz-Wetzlar microhardness tester Microhardness analysis was conducted by means of the Leitz-Wetzlar microhardness tester (LEICA, Wetzlar, Germany) on a sample of the cross-section of the coating/substrate system. The (LEICA, Wetzlar, Germany) on a sample of the cross-section of the coating/substrate system. The
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Microhardness analysis was conducted by means of the Leitz-Wetzlar microhardness tester (LEICA, Wetzlar,was Germany) on athe sample of the cross-section of the coating/substrate system. Vickers method used, with indenter weighed down with a mass of 100 g. In order to The Vickers method was used, with the indenter weighed down with a mass of 100a g. In order determine the uncertainty of measurement, t-student distribution was conducted, with confidence to determine the of measurement, t-student distribution was that conducted, with confidence level assumed atuncertainty 95%. The obtained results were used to create a graph presents theadistribution level assumed at 95%. The obtained results were used to create a graph that presents the distribution of microhardness. of microhardness. The microhardness distribution presented in Figure 5 indicates significant difference in the The microhardness distribution presented Figure 5 indicates in the hardness of the substrate material and the coating.inNear the boundary of significant the coating difference and the substrate hardness of the substrate material and the coating. Near the boundary of the coating and the substrate material, hardness reaches the highest average value at 265 HV0.1 halfway through the thickness of material, hardness reaches the highest valueatatthe 265 surface, HV0.1 halfway through thickness the the coating the hardness is lower ataverage 230 HV0.1; hardness rises the to 258 HV0.1.ofThe coating the hardness is lower at 230 HV0.1; at the surface, hardness rises to 258 HV0.1. The differences differences in hardness result from the non-uniformity in the structure of the coating and the different in hardnessof result the non-uniformity structure of the During coating the andanalysis, the different conditions conditions heatfrom dissipation in the processinofthe coating buildup. no values were of heat dissipation the process offor coating buildup. During analysis, nophase, valueswhose were recorded that recorded that are in characteristic the occurrence of an the intermetallic hardness is are characteristic for the occurrence of an intermetallic phase, whose hardness is significantly higher significantly higher than the results obtained, which allows us to assume that the synthesis of than the results obtained, allows to assume that the synthesis of intermetallic intermetallic Fe-Al phaseswhich occurred onlyuslocally, on the inter-phase boundary of grains Fe-Al in the phases Al and occurred Fe matrix.only locally, on the inter-phase boundary of grains in the Al and Fe matrix.
Figure 5. Distribution of microhardness in substrate material and the arc arc sprayed sprayed Fe-Al Fe-Al coating. coating.
3.3. 3.3. X-ray X-RayDiffraction Diffraction(XRD) (XRD)Analysis Analysis In In order order to to analyze analyze the the phase phase structure structure of of the the coatings coatings in in the the first first stage, stage, XRD XRD analysis analysis was was performed. Figure 6 presents a diffraction pattern that implies that the phase structure of the analyzed performed. Figure 6 presents a diffraction pattern that implies that the phase structure of the analyzed coating metallic phases—based phases—based on on the the Fe Fe (bcc) (bcc) and and Al Al (fcc) (fcc) structure. structure. In In reality, reality, coating includes includes two two main main metallic these are Fe(Al) and Al(Fe) solutions, with the dominant share of the solvent, while the solid these are Fe(Al) and Al(Fe) solutions, with the dominant share of the solvent, while the solid solution solution Fe(Al) has a significantly larger difference in the lattice constant, compared to pure suggests Fe—this Fe(Al) has a significantly larger difference in the lattice constant, compared to pure Fe—this suggests a larger share of Al in this phase. Crystal oxide phases can also be seen—based on the a larger share of Al in this phase. Crystal oxide phases can also be seen—based on the structures of structures of wustite (FeO) and magnetite (Fe O ). XRD analysis does not confirm a significant share 4 wustite (FeO) and magnetite (Fe3O4). XRD 3analysis does not confirm a significant share (above (above sensitivity of the method) in the structure of the coating of intermetallic phases the Fe-Al sensitivity of the method) in the structure of the coating of intermetallic phases from thefrom Fe-Al system. system. The approximate share by volume of the crystal phase in the structure, identified with the The approximate share by volume of the crystal phase in the structure, identified with the XRD XRD method, is approximately method, is approximately 5%. 5%.
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Figure 6. X-ray X-ray diffraction (XRD) diffraction pattern of the arc sprayed Fe-Al coating. coating.
3.4. EDS Analysis Analysis 3.4. EDS Figure Figure 77 presents presents the the SEM SEM images images of of the the crystal crystal precipitations precipitations in in the the inter-phase inter-phase boundary boundary of of grains the Fe Fe matrix matrix and and the the grains grains on on the the Al Al matrix matrix that that are are present present throughout throughout the volume of the grains on on the the volume of the analyzed analyzed coatings, coatings, but but with with aa different different intensity. intensity.
Figure 7. Crystal Crystal precipitation in the inter-phase boundary of crystals on a Fe and Al matrix.
Due precipitations with a shade of grey intermediate between the dark, to the themass masscontrast contrastofofthe the precipitations with a shade of grey intermediate between the Due to corresponding to Al, to and light, corresponding to Fe, to it is that the precipitations are a dark, corresponding Al,the and the light, corresponding Fe,assumed it is assumed that the precipitations crystallization of Fe-Al. the first of the analysis of the phaseof structure of the crystallization are a crystallization of In Fe-Al. In stage the first stage of the analysis the phase structure of the precipitations in Figure 8, aninEDS analysis wasanalysis conducted order to in determine the linear crystallization shown precipitations shown Figure 8, an EDS wasin conducted order to determine distribution of elements the areain ofthe crystallization precipitations. the linear distribution ofin elements area of crystallization precipitations.
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Figure 8. Linear distribution of elements elements in in the thecrystal crystalboundary, boundary,confirming confirmingthe thepresence presence of the FeFigure 8. 8. Linear Linear distribution distribution of ofof the Fe-Al Figure of elements in the crystal boundary, confirming the presence the FeAl phase, with the composition of about about 50–50% at. phase, with thethe composition of about 50–50% at. at. Al phase, with composition of 50–50%
For energy-dispersiveX-ray X-ray spectroscopy (EDS) analysis, method for determining determining the For energy-dispersive spectroscopy (EDS) analysis, a method for determining the chemical For energy-dispersive X-ray spectroscopy (EDS) analysis, aa method for the chemical composition was chosen that was conducted along the line placed in such a way that it went composition was chosen that was conducted along the line placed in such a way that it went through chemical composition was chosen that was conducted along the line placed in such a way that it went through the characteristic characteristic areas of the the structure. structure. The placement placement ofisthe the line is is shown inimage the SEM SEM image the characteristic areas of the structure. The placement of the lineof shown inshown the SEM fragment. through the areas of The line in the image fragment. The obtained results of quantitative linear distributions (shown in Figures 8 and 9) on the The obtained results of quantitative linear distributions (shown in Figures 8 and 9) on the phase fragment. The obtained results of quantitative linear distributions (shown in Figures 8 and 9) on the phase boundary have shown the presence in the structure of both oxide phases as well as intermetallic boundary have shown the presence in the structure of both oxide phases as well as intermetallic phases phase boundary have shown the presence in the structure of both oxide phases as well as intermetallic phases from the Fe-Alwith system, with atomic varying atomic share of iron iron and and aluminum, including from thefrom Fe-Althe system, a varying share of ironshare and aluminum, including approximately phases Fe-Al system, with aa varying atomic of aluminum, including approximately 50–50% and 80–20%. 50–50% and 80–20%. approximately 50–50% and 80–20%.
Figure 9. Linear distribution ofof the Fe-Al Figure 9. Linear Linear distribution of elements in in the thecrystal crystalboundary, boundary,confirming confirmingthe thepresence presence of the FeFigure of elements elements in the crystal boundary, confirming the presence the Fephase, with a composition of about 80–20%. Al phase, with a composition of about 80–20%. Al phase, with a composition of about 80–20%.
The results results of of EDS EDS analysis analysis have have also also shown shown that, that, apart apart from from metallic metallic phases, phases, oxide oxide phases phases are are The The results of EDS analysis have also shown that, apart from metallic phases, oxide phases are present in the layer structure as well. These are oxidized Al and Fe, denoted with different shades present in in the the layer layer structure structure as as well. well. These These are are oxidized oxidized Al Al and and Fe, Fe, denoted denoted with with different different shades shades of of present of gray in the SEM images. The subsequent researchresults resultsconcern concernthe thearea areawith withaa more more complex complex gray in the SEM images. The subsequent research gray in the SEM images. The subsequent research results concern the area with a more complex structure. The presented in Figure 8 indicate the presence of local structure. The linear lineardistributions distributionsofof ofelements elements presented in Figure Figure indicate the presence presence of oxide local structure. The linear distributions elements presented in 88 indicate the of local areas. areas. EDS analysis does not make itmake possible to precisely determine what kind of kind oxides are formed oxide EDS analysis does not it possible to precisely determine what of oxides are oxide areas. EDS analysis does not make it possible to precisely determine what kind of oxides are in the layer’s structure. In order to identify the chemical components presentpresent in the in volume of the formed in the layer’s structure. In order to identify the chemical components the volume formed in the layer’s structure. In order to identify the chemical components present in the volume coating, the Mössbauer spectroscopy technique was used. of the coating, coating, the Mössbauer Mössbauer spectroscopy technique was used. used. of the the spectroscopy technique was
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10 presents morphology of the indicates aa substantially smaller Figure 10 thethe morphology of the whichwhich indicates a substantially smaller diversity 10presents presents the morphology of surface, the surface, surface, which indicates substantially smaller diversity of phases than in the volume of the coating, which confirms the impact of the heat cycle of of phases than in the volume of the coating, which confirms the impact of the heat cycle of the coating diversity of phases than in the volume of the coating, which confirms the impact of the heat cycle of the coating after spraying on its phase structure, in the context of a system with unequal weight as after spraying onspraying its phaseon structure, instructure, the context unequalwith weight as well as heat the coating after its phase in of thea system context with of a system unequal weight as well as as heat heatof stimulation of intermetallic intermetallic phases. Figurethe 10map presents the map map of element elementcreated distribution, stimulation intermetallic phases. Figure 10 presents of element distribution, using well stimulation of phases. Figure 10 presents the of distribution, created using the EDS method on the outer surface of the sprayed coating. The figure’s colors indicate the EDS method on the outer surface of the sprayed coating. The figure’s colors indicate the distribution created using the EDS method on the outer surface of the sprayed coating. The figure’s colors indicate the Fe the indicates the of both of and Al, theof intermediate indicates thecolor occurrence of both components the phase’s theFedistribution distribution of Fe and and Al, Al, color the intermediate intermediate color indicates the occurrence occurrence ofwithin both components components within the phase’s volume. Such places have been indicated with arrows. Areas with no were volume. Such places have been indicated with arrows. Areas with no color were created as a result within the phase’s volume. Such places have been indicated with arrows. Areas with no color color were created as a result of an uneven surface. On the surface of the coating, the particular phases are of an uneven surface. Onuneven the surface of the the particular phasesthe areparticular arrangedphases randomly. created as a result of an surface. Oncoating, the surface of the coating, are arranged randomly. No segregation ofobserved, the phases phases has been been observed, either. Both larger and smaller No segregation of theNo phases has beenof either. Bothobserved, larger andeither. smaller areas of the particular arranged randomly. segregation the has Both larger and smaller areas the particular phases are Only commonly phases Only Fe is commonly sphericalpresent form. in areas of ofare thevisible. particular phases are visible. visible.present Only Fe Feinis isthe commonly present in the the spherical spherical form. form.
Figure on the the surface surface of of the the coating. coating. Figure 10. 10. Map Map of of the the distribution distribution of of the the chemical chemical components components present present on
3.5. 3.5. Mössbauer Mössbauer Spectroscopy Spectroscopy In coatings, In the the next next stage stage of of the the phase phase analysis analysis of of the the coatings, coatings, the the Mössbauer Mössbauer effect effect spectroscopy spectroscopy measurements were performed for the same surfaces on which a SEM analysis presented in in Figure 11 were performed for the same surfaces on which a SEM analysis presented Figure measurements were performed for the same surfaces on which a SEM analysis presented in Figure was conducted. The purpose of the analysis was to image the presence of the phases and the 11 11 was was conducted. conducted. The The purpose purpose of of the the analysis analysis was was to to image image the the presence presence of of the the phases phases and the comparison of the chemical composition on the surface and inside the coating. surface and inside the coating. comparison of the chemical composition on the surface and inside the coating.
Figure Figure 11. 11. Example Example SEM SEM image image of of the the sprayed sprayed surface surface of of the the coatings. coatings.
For two randomly selected selected samples of of the sprayed-on sprayed-on coatings, measurements measurements of the the conversion For For two two randomly randomly selected samples samples of the the sprayed-on coatings, coatings, measurements of of the conversion conversion electron Mössbauer spectroscopy spectroscopy (CEMS) were were conducted (Figure (Figure 12), which provided information electron electron Mössbauer Mössbauer spectroscopy (CEMS) (CEMS) were conducted conducted (Figure 12), 12), which which provided provided information information from from the the surface surface layer layer with with the the thickness thickness of of approximately approximately 200 200 nm nm (average (average measurement). measurement). Despite Despite
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Metalsthe 2018, 8, x FORlayer PEERwith REVIEW 9 ofthe 12 from surface the thickness of approximately 200 nm (average measurement). Despite fact that CEMS spectra have a high background, it was possible to reliably match the components thespectra, fact thatboth CEMS spectraand havenon-magnetic, a high background, was possible to reliably match thequalitatively, components of magnetic as wellitas determine, quantitatively and of spectra, both magnetic and non-magnetic, as well as determine, quantitatively and qualitatively, the distribution of Fe atoms in the various phases. the distribution of Fe atoms the various phases. CEMS spectra have beenindeveloped with the use of four components: CEMS spectra have been developed with the use of four components: (1). Sextet with with aa hyperfine hyperfine field (1). Sextet field 32.6 32.6 T T (sample (sample 1) 1) and and 32.7 32.7 T T (sample (sample 2), 2), (2). Sextet with a hyperfine field 29.3 T (sample 1) and 29.8 T (sample 2), (2). (sample 2), (3). (3). Quadrupole doublet with with quadrupole quadrupole splitting splitting values valuesof ofapproximately approximately0.4 0.4mm/s mm/s and isometric isometric shift of 0.23 mm/s, mm/s, (4). Quadrupole ofof 0.80 mm/s andand isometric shiftshift of 0.91 (4). Quadrupole doublet doublet with withquadrupole quadrupolesplitting splittingvalues values 0.80 mm/s isometric of mm/s (sample 1). 1). 0.91 mm/s (sample
Figure 12. 12. Results of Mössbauer spectroscopy. spectroscopy.
The phases in the samples was done ondone the basis hyperfine Theidentification identificationof of phases in analyzed the analyzed samples was on of the basis ofparameters hyperfine determined for the particular components of the spectra. In the case of the sextet (1) the values of the parameters determined for the particular components of the spectra. In the case of the sextet (1) the hyperfine magnetic field are somewhat lower than the characteristic value for the pure α-Fe phase values of the hyperfine magnetic field are somewhat lower than the characteristic value for the pure (32.95 T), which why the sextet assigned phase bcc Fe, where thewhere Al atoms do atoms not occur in α-Fe phase (32.95isT), which is whyisthe sextet istoassigned to phase bcc Fe, the Al do not the immediate vicinity of the Fe atoms, however they may be present in the remote vicinity [19,20]. occur in the immediate vicinity of the Fe atoms, however they may be present in the remote vicinity Significantly smaller smaller values of the field offield the hyperfine sextet (2) indicate the formation of solid [19,20]. Significantly values of the of the hyperfine sextet (2) indicate the formation of solution on theon basis iron—bcc Fe(Al) Fe(Al) with anwith average share ofshare Al ofofapproximately 15% [19,20]. solid solution the of basis of iron—bcc an average Al of approximately 15% Hyperfine parameters of the quadrupole doublet doublet (3), observed in the central the spectra, [19,20]. Hyperfine parameters of the quadrupole (3), observed in thesection centralof section of the suggest the creation of an Al-rich phase, such as Al Fe [21] or an unordered FeAl phase [20]. It should 5 2 as Al5Fe2 [21] or an unordered FeAl phase spectra, suggest the creation of an Al-rich phase, such [20]. be noted that the ordered intermetallic phase FeAl with a regular structure (B2) has a single line with an It should be noted that the ordered intermetallic phase FeAl with a regular structure (B2) has a single isometric shift of 0.28 mm/s [20,21]. The observation of a quadrupole doublet in the measured spectra line with an isometric shift of 0.28 mm/s [20,21]. The observation of a quadrupole doublet in the indicates presence of a phase localofsurroundings of iron have a significantlyoflower measuredthe spectra indicates the where presence a phase where local surroundings iron level haveofa symmetry than in the cubic structure. In sample 1, a small fraction of iron oxide FeO was identified significantly lower level of symmetry than in the cubic structure. In sample 1, a small fraction of iron (component 4), in addition, trace amounts ofaddition, Fe3 O4 cannot ruled out. measurement of oxide FeO was identified (component 4), in trace be amounts of FeThe 3O4 average cannot be ruled out. The
average measurement of the surface layer made it possible to conduct quantitative analysis of the phase composition of both samples: sample 2 has a smaller fraction of the component originating from the bcc Fe phase, with a small share of Al, while a visibly higher fraction of the solid solution bcc Fe(Al) (relative fraction in the spectrum approximately 50%, compared to approximately 30% for
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the surface layer made it possible to conduct quantitative analysis of the phase composition of both samples: sample 2 has a smaller fraction of the component originating from the bcc Fe phase, with a small share of Al, while a visibly higher fraction of the solid solution bcc Fe(Al) (relative fraction in the spectrum approximately 50%, compared to approximately 30% for sample 1) and a slightly lower fraction of the Fe-Al phase rich in Al (relative fraction in the spectrum 7% compared to 12% for sample 1). It was determined that in sample 2, components Fe and Al reacted to a slightly larger extent than in sample 1. These differences may probably be explained by the differences in the shaping of the sprayed surface of the coating (uneven surface) that the CEMS measurement originated from. 4. Summary and Conclusions A process of arc spraying was realized while simultaneously using two different electrode wires Fe and Al. After optimizing the parameters, composite coatings Fe-Al were created in the process, with the coating including in its structure intermetallic Fex Aly phases with an insignificant fraction by volume. By independently melting two wires, one made of iron and one of aluminum, the thermodynamic conditions were created for intermetallic phases to emerge. The resulting coatings have a multi-phase structure. The structure is dominated by solid solutions based on iron and aluminum; many iron oxides and aluminum oxides are visible as well. XRD analysis did not show an occurrence of intermetallic phases in the minimal volume identifiable by this method, in order for XRD analysis to indicate the existence of a given phase, its share by volume in the analyzed structure should exceed 5%, which did not occur during the experiment. The conducted detailed EDS analysis as well as the measurements using the Mössbauer spectroscopy method have shown the effect of synthesis between Fe and Al and the presence of the intermetallic Fe-Al phase. The method used by the authors for manufacturing coatings from the Fe-Al system is an alternative for the solution based on expensive metallic powders that are used in industrial conditions. Further research will be directed towards optimizing the spraying process so that coatings are manufactured in-situ with a higher fraction of intermetallic phases by volume. In the next stage of research, thermal stimulation of Fe and Al synthesis will be conducted. Author Contributions: T.C. and P.S. designed and performed the experiments. M.C., D.G. and A.P. tested microstructure A.G. prepared Mössbauer spectroscopy. Funding: The publication of the study was cofunded using the statutory subsidy of the Faculty of Production Engineering of the Warsaw University of Technology in 2018. Acknowledgments: Thanks are given to the assistance from the technical specialist Eng. Piotr Burcon from SciTeeX. Conflicts of Interest: The authors declare no conflict of interest.
References 1. 2. 3. 4. 5. 6. 7. 8.
Wang, H.; Li, C.; Yang, G.; Li, C. Cold spraying of Fe/Al powder mixture: Coating characteristics and influence of heat treatment on the phase structure. Appl. Surf. Sci. 2008, 255, 2538–2544. [CrossRef] Senderowski, C.J. Nanocomposite Fe-Al intermetallic coating obtained by gas detonation spraying of milled self-decomposing powder. J. Therm. Spray Technol. 2013, 23, 1124–1134. [CrossRef] Czuprynski, ´ A.; Gorka, J.; Adamiak, M. Examining properties of arc sprayed nanostructured coatings. Metalurgija 2016, 55, 173–176. Gorka, J.; Czuprynski, ´ A.; Adamiak, M. Properties and structure of nanocrystalline layers obtained by manual metal arc welding (MMA). Arch. Metall. Mater. 2017, 62, 1479–1484. [CrossRef] Adamiak, M.; Tomiczek, B.; Gorka, J.; Czuprynski, ´ A. Joining of the AMC composites reinforced with Ti3 Al intermetallic particles by resistance butt welding. Arch. Metall. Mater. 2016, 61, 847–851. [CrossRef] Beczkowski, R. Effect of cladding parameters on the hardness of bimetal plates. Metalurgija 2017, 56, 59–62. Casalino, G.; Leo, P.; Mortello, M.; Perulli, P.; Varone, A. Effects of laser offset and hybrid welding on microstructure and IMC in Fe–Al dissimilar welding. Metals 2017, 7, 282. [CrossRef] Chmielewski, T.; Golanski, ´ D. New method of in-situ fabrication of protective coatings based on Fe–Al intermetallic compounds. Proc. Inst. Mech. Eng. B J. Eng. Manuf. 2011, 225, 611–616. [CrossRef]
Metals 2018, 8, 1059
9. 10. 11. 12. 13. 14. 15. 16.
17.
18. 19. 20. 21. 22.
23. 24. 25. 26.
27. 28. 29. 30.
31. 32.
11 of 12
Shishkovsky, I.; Missemer, F.; Kakovkina, N.; Smurov, I. Intermetallics synthesis in the Fe–Al system via layer by layer 3D laser cladding. Crystals 2013, 3, 517–529. [CrossRef] Shishkovsky, I. Laser-Controlled Intermetallics Synthesis during Surface Cladding. In Laser Surface Engineering; Woodhead Publishing: Cambridge, UK, 2014; pp. 237–286. Sun, K.; Cheng, J.; Liu, X.; Fang, L.; Ma, L. In-Situ fabrication of Fe–Al intermetallic coating by laser remelting. J. Mechatron. 2014, 2, 207–211. [CrossRef] Senderowski, C.; Zasada, D.; Durejko, T.; Bojar, Z. Characterization of as-synthesized and mechanical milled Fe-Al powders produced by the self-disintegration method. Powder Technol. 2014, 263, 96–103. [CrossRef] Nunobiki, M.; Harada, Y.; Okuda, K. Production of Fe-Al alloy coat on steel block by scanning laser beam. Adv. Mat. Res. 2014, 1017, 794–799. [CrossRef] ´ ´ Swiercz, R.; Oniszczuk-Swiercz, D. Experimental investigation of surface layer properties of high thermal conductivity tool steel after electrical discharge machining. Metals 2017, 7, 550. [CrossRef] Xu, B.; Zhu, S.; Ma, S.; Zhang, W.; Liu, W. Sliding wear behavior of Fe-Al and Fe-Al/WC coatings prepared by high velocity arc spraying. Wear 2004, 257, 1089–1095. [CrossRef] Sattari, B.; Shamanian, M.; Ashrafi, A.; Salehi, M.; Salimijazi, F. Effect of number of passes on the corrosion behaviour of Fe/Al Surface composites produced by plasma spraying and friction stir processing. J. Mater. Process. Technol. 2017, 250, 35–44. [CrossRef] Chmielewski, M.; Nosewicz, S.; Pietrzak, K.; Rojek, J.; Strojny-N˛edza, A.; Mackiewicz, S.; Dutkiewicz, J. Sintering behavior and mechanical properties of NiAl, Al2 O3 , and NiAl-Al2 O3 composites. J. Mater. Eng. Perform. 2014, 23, 3875–3886. [CrossRef] Amiriyan, M.; Alamdari, H.; Blais, C.; Savoie, S.; Schulz, R. Dry sliding wear behavior of Fe3 Al and Fe3 Al/TiC coatings prepared by HVOF. Wear 2015, 342, 154–162. [CrossRef] Pẽrez Alcazar, G.A.; Galvão da Silva, E. Mössbauer effect study of magnetic properties of Fe1−q Alq , 0 < q ≤ 0.5, alloys in the disordered phase. J. Phys. F: Met. Phys. 1987, 17, 2323–2335. Krasnowski, M.; Grabias, A.; Kulik, T. Phase transformations during mechanical alloying of Fe–50% Al and subsequent heating of the milling product. J. Alloys Compd. 2006, 424, 119–127. [CrossRef] Nasu, S.; Gonser, U.; Preston, R.S. Defects and phases of iron in aluminium. J. Phys. Colloq. 1980, 41, 385–386. [CrossRef] Senderowski, C.; Bojar, Z.; Szymanski, ´ K.; Formanek, B. Badania struktury i wła´sciwo´sci powłok wielowarstwowych typu NiAl/FeAl i NiCr/FeAl osadzanych metoda˛ HVOF. Inz˙ ynieria Materiałowa 2008, 6, 611–614. Jozwik, P.; Bojar, Z.; Kołodziejczak, P. Microjoining of Ni3 Al based intermetallic thin foils. Mater. Sci. Technol. 2010, 26, 473–477. [CrossRef] Gontarz, G. Warstwy intermetaliczne typu Fe-Al wytwarzane metoda˛ TIG AC. Weld. Technol. Rev. 2013, 85, 8–11. [CrossRef] Lotfian, S.; Rolink, G.; Weisheit, A.; Palm, M. Chemically graded Fe-Al/steel samples fabricated by laser metal deposition. MRS Adv. 2017, 2, 1393–1398. [CrossRef] Aryanto, D.; Wismogroho, A.S.; Sudiro, T. Structure Evolution of Fe-50%Al Coating Prepared by Mechanical Alloying. In Proceedings of the Journal of Physics: Conference Series, Bandung, Indonesia, 19–20 August 2016. Aryanto, D.; Sudiro, T.; Wismogroho, A.S. Structure and High Temperature Oxidation of Mechanical Alloyed Fe-Al Coating. In Proceedings of the AIP Conference Proceedings, Semarang, Indonesia, 6–7 October 2015. Karczewski, K.; St˛epniowski, W.J.; Salermo, M. Fabrication of FeAl intermetallic foams by tartaric acid-assisted self-propagating high-temperature synthesis. Materials 2018, 11, 621. [CrossRef] [PubMed] Kim, J.-M.; Ha, T.-H.; Park, J.-S.; Kim, H.-G. Effect of laser surface treatment on the corrosion behavior of FeCrAl-coated TZM alloy. Metals 2016, 6, 29. [CrossRef] Golanski, ´ D.; Dymny, G.; Kujawinska, ´ M.; Chmielewski, T. Experimental investigation of displacement/strain fields in metal coatings deposited on ceramic substrates by thermal spraying. Solid State Phenom. 2016, 240, 174–182. Chmielewski, T.; Golanski, ´ D. The role of welding in the remanufacturing process. Weld. Int. 2015, 29, 861–864. [CrossRef] Chmielewski, T.; Golanski, ´ D. Selected properties of Ti coatings deposited on ceramic AlN substrates by thermal spraying. Weld. Int. 2013, 27, 604–609. [CrossRef]
Metals 2018, 8, 1059
33. 34. 35. 36. 37.
12 of 12
Babul, T. Temperature of NiCrBSi powder particles detonation sprayed-theory and practice. Arch. Metall. Mater. 2014, 59, 1107–1110. [CrossRef] Presz, W.; Cacko, R. Determination of Material Distribution in Heading Process of Small Bimetallic Bar. In Proceedings of the AIP Conference Proceedings, Palermo, Italy, 23–25 April 2018. Presz, W.; Cacko, R. Bimetallic micro-punches for micro-blanking processes. Arch. Metall. Mater. 2018, 63, 29–34. Siemaszko, D.; Kuzia, J. The influence of large particles of iron powder on the microstructure and properties of FeAl intermetallic phase. Intermetallics 2019, 104, 16–23. [CrossRef] Pietrzak, K.; Kalinski, D.; Chmielewski, M. Microstructure and Mechanical Properties of Hot-Pressed Fe3 Al/Al2 O3 and Fe3 Al/TiC Composites. In Proceedings of the 15th European Conference on Composite Materials, Venice, Italy, 24–28 June 2012. © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
