Study on Surface Roughness of Gcr15 Machined by Micro ... - MDPI

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Study on Surface Roughness of Gcr15 Machined by Micro-Texture PCBN Tools Chen Pan, Qinghua Li *, Kaixing Hu, Yuxin Jiao and Yumei Song College of Machinery and Vehicle Engineering, Changchun University, Changchun 130022, China; [email protected] (C.P.); [email protected] (K.H.); [email protected] (Y.J.); [email protected] (Y.S.) * Correspondence: [email protected]; Tel.: +86-131-960-01761 Received: 5 September 2018; Accepted: 13 September 2018; Published: 17 September 2018

Abstract: This paper applies micro textures to the rake face of PCBN (Polycrystalline Cubic Boron Nitride) tools, including three types of micro textures that are microgroove textures vertical to the cutting edge, microgroove textures parallel to the cutting edge, and microhole textures. In this paper, the effects of different cutting speeds on the surface quality of hardened bearing steel GCr15 by dry turning with non-texture PCBN tools and micro-texture PCBN tools are studied, and the surface roughness values obtained by different micro textures were compared and analyzed. The results showed that, compared to that of non-texture tools, the influence degree of the micro-texture tools on the machined surface roughness was different. The microhole texture and vertical microgroove texture were able to effectively reduce the surface roughness of the workpiece, and microhole texture had the best effective influence on surface roughness, but the parallel microgroove texture increased surface roughness. The influence of cutting speeds on surface roughness was different due to different types of micro textures. The influence of micro textures on surface roughness has huge potential for tool applications. Keywords: PCBN tools; microhole; microgroove; surface roughness

1. Introduction Surface quality, as one of the most important indexes for measuring cutting performance, has always been the focus of cutting research. Scholars have continuously studied and analyzed the factors affecting surface quality, such as the plastic deformation of the workpiece, the geometric shape of the tool, the cutting parameters, and the cooling modes, and combined with the roughness prediction models, the best processing scheme is successfully summed up to get good surface quality. In the study of aluminum alloy surface roughness tests, Wan et al. concluded that spindle speed was the most important factor affecting surface roughness when milling aluminum alloy 6061 at a high speed, and the milling parameters for obtaining the best surface quality were obtained [1]. Joshua et al. found that the feed had the greatest influence on surface roughness, followed by the spindle speed, and the cutting depth had the smallest effect on surface roughness during end milling of aluminum 6061 under minimum quantity lubrication. At the same time, the combination of feed and spindle speed was more favorable to obtaining good surface quality [2]. The influence of milling speed on surface roughness was studied by Bon¸tiu et al. when milling aluminum alloy 7136 [3]. Luo et al. found that passivated PCD (polycrystalline diamond) tools in turning aluminum alloy 1060 could reduce surface roughness [4]. Additionally, in the study of the surface roughness of titanium alloy, Wang et al. showed that applying ultrasonic torsional vibration could obviously reduce the surface roughness of titanium alloy TC11, and concluded that large amplitude and low milling speed were beneficial to reducing surface roughness [5]. In the test of milling titanium alloy Ti6Al4V, Li et al. found Machines 2018, 6, 42; doi:10.3390/machines6030042

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that the roughness of a milled surface increased with the increase of milling speed, feed per tooth, milling width, and milling depth [6]. Oliaei et al. investigated the influence of built-up edge formation on surface roughness through microscale orthogonal cutting tests on titanium alloy Ti6Al4V, and found that the influence of built-up edge on surface roughness varied, depending on the cutting speed and uncut chip thickness [7]. Du et al. studied the influence of the rake angle, the clearance angle, and the helix angle of the carbide milling cutter on the surface integrity of titanium alloy TB17, and concluded that surface roughness increased when increasing the rake angle, the surface roughness reduced when increasing the clearance angle, and surface roughness showed the trend of first decreasing and then increasing with the increase of the helix angle [8]. In the study of the roughness of the turning surface, Wang et al. used the regression analysis method and established the LS-SVM forecast model in the precision turning mirror surface roughness test; the results showed that the effects of tool nose radius and feed were more significant than those of depth of cut on surface roughness [9]. The surface roughness of the precision turning optical lens was studied using response surface methodology. Li et al. concluded that the tool nose radius had the greatest influence on surface roughness, followed by the feed and the cutting depth [10]. Luo concluded that the most significant effect on surface roughness came from the feed speed; the cutting speed was second, but the cutting depth had no direct effect on the surface roughness while turning high strength steel 58SiMn [11]. Khatri et al. attempted to improve the surface finish of diamond turned silicon with magneto-rheological finishing, and concluded that a smaller gap, high wheel speed, and high current result in minimum surface roughness [12]. In the study of the roughness of hardened steel, Suresh et al. made experiments based on the central composite design (CCD) concept of response surface methodology (RSM). During turning of hardened steel with coated ceramic tool, the experimental results showed that the feed had the greatest influence on surface roughness, followed by the cutting speed, and the cutting depth had the least influence [13]. Liu et al. pointed out that surface roughness would rise along with the speed of grinding wheel, and workpiece increased within a certain range when grinding hardened steel GCr15 [14]. Krolczyk et al. researched the surface morphology of duplex stainless steel using the method Power Spectral Density for dry and MQL/MQCL (Minimum Quantity Lubrication) turning process [15], Krolczyk concluded in the following study that the application of the MQCL method can lead to the reduction of 3D surface roughness parameters compared to values reached after dry machining, and surfaces machined with the use of the MQCL technique can be characterized by a high wear resistance [16]. Liu et al. proposed a ground surface roughness measurement method to address current problems in the use of machine vision technology to measure roughness, and the results demonstrated that the surface roughness measurement method had relatively high accuracy and a relatively wide measurement range [17]. Chen et al. demonstrated a Nested-ANN (Artificial Neural Network) model predicting surface roughness, and pointed out that the nested-ANN uses less input variables to obtain superior prediction accuracy than other models [18]. In view of the current research status and research methods of surface roughness in literature, this paper uses the micro-texture method, that is, the micro dimension textures processing on the rake face of tools, and studies the influence of micro textures on the surface roughness of the workpiece. 2. Type of Micro Textures and Test Scheme 2.1. Type of Micro Textures In order to study the actual situation of cutting parts of micro texture cutting tools, three micro textures were processed on the rake face of PCBN tools with the Fiber Laser Marking machine (FLY-M10F) fully enclosed rotary optical fiber laser marking machine. The types of micro textures included 30 µm microgrooves perpendicular to the cutting edge, 40 µm microgrooves parallel to the cutting edge, and micro holes of 120 µm in diameter. Table 1 is the micro-texture size. As shown in Figure 1, the blade is the CNGA120408 PCBN tool. The WYKO N7910 optical profiler was used to

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cutting edge, and micro holes of 120 µm in diameter. Table 1 is the micro-texture size. As shown in cutting1,edge, and micro of 120 µmPCBN in diameter. Table 1 is the micro-texture size. As in Figure the blade is theholes CNGA120408 tool. The WYKO N7910 optical profiler wasshown used to Figure 1, the blade is the CNGA120408 PCBN tool. The WYKO N7910 optical profiler was used to detect the three-dimensional texture of the micro textures, as shown in Figure 2: Surface Machines 42 3 of 11 detect 2018, the 6,three-dimensional texture of the micro textures, as shown in Figure 2: Surface morphology of micro-texture tools. morphology of micro-texture tools. 1. micro The micro textures’ size. detect the three-dimensional textureTable of the textures, as shown in Figure 2: Surface morphology Table 1. The micro textures’ size. of micro-texture tools. Width/Diameter Depth Distance from the Number Type of Microtexture Width/Diameter Depth Distance from(µm) the (µm) (µm) Cutting Edge Number Type of Microtexture Table 1. The micro textures’ size. (µm) (µm) Cutting Edge (µm) Vertical microgrooves 30 5 200 10 Vertical 30 (µm) 200 10 Type ofmicrogrooves Microtexture Width/Diameter Depth (µm) Distance from the Cutting Edge (µm) Number Parallel microgrooves 40 55 200 8 Vertical microgrooves 30 5 200 10 Parallel microgrooves 40 5 200 Microholes 350 988 Parallel microgrooves 40120 5 5 200 Microholes 350 99 Microholes 120120 5 5 350

Figure Figure 1. 1. The The CNGA120408 CNGA120408 PCBN PCBN tool. tool. Figure 1. The CNGA120408 PCBN tool.

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(c) (c) Figure 2. Surface Surface morphology morphology of of micro-texture micro-texture tools: tools: (a) (a) 30 30 µm µm vertical vertical microgrooves; microgrooves; (b) (b) 40 40 µm µm Figure Figure 2. Surface morphology of micro-texture (a) 30 µm vertical microgrooves; (b) 40 µm of 120 µm diameter. parallel microgrooves; (c) microholes µm intools: diameter. parallel microgrooves; (c) microholes of 120 µm in diameter.

2.2. Test Parameters and Solutions 2.2. Test Parameters and Solutions 2.2. Test Parameters and Solutions In this cutting test, the CA6140 lathe was used for turning hardened steel GCr15 with hardness of In this cutting test, the CA6140 lathe was used for turning hardened steel GCr15 with hardness ◦ , the clearance angle was 58 HRC.this Figure 3 is test, the GCr15 workpiece. rake angle of the tool was −6steel cutting the CA6140 lathe The wasThe used forangle turning hardened GCr15 with hardness of◦ 58 In HRC. Figure 3 is the GCr15 workpiece. rake of the tool was −6°, the clearance angle 6of ,58 theHRC. feed Figure was 0.13mm/r, and theworkpiece. cutting depth was 0.2 mm.ofThe specific plan was as follows: angle is the GCr15 The rake angle the tool was −6°, the clearance was 6°, the feed was 0.1 mm/r, and the cutting depth was 0.2 mm. The specific plan was as follows: was 6°, the feed was 0.1 mm/r,steel and the cutting depthcarried was 0.2 mm. The specific plan was as follows: (1). (1). Dry Drycutting cuttingofofhardened hardened steelGCr15 GCr15test testwas was carried out out using using normal normal PCBN PCBN tools tools (normal (normal (1). PCBN Dry cutting of hardened steel GCr15 test was carried out using normal PCBN tools (normal tools: Non-micro texture PCBN tools) at different cutting speeds of v 1 = 60 m/min, v2 = 72 PCBN tools: Non-micro texture PCBN tools) at different cutting speeds of v1 = 60 m/min, PCBN tools: Non-micro texture PCBN tools) at different cutting speeds of v1 = 60 m/min, v2 = 72 m/min, v 3 = 85 m/min; v2 = 72 m/min, v3 = 85 m/min; m/min, v3 = 85 m/min; (2). The tools, parallel (2). Thecutting cuttingtests tests of of micro-texture micro-texture PCBN PCBN tools tools (vertical (vertical microgroove microgroove PCBN PCBN parallel (2). microgroove The cutting tests of micro-texture PCBN tools (vertical microgroove PCBN tools, tools, and parallel PCBN tools, and microhole PCBN tools) were carried out respectively, the microgroove PCBN tools, and microhole PCBN tools) were carried out respectively, and microgroove PCBN tools, and microhole PCBN tools) were carried out respectively, and the the surface roughness of the workpiece was measured with a WYKO N7910 optical profiler, all of which were compared to the test of normal PCBN tools.

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surface roughness of the workpiece was measured with a WYKO N7910 optical profiler, all of 4 of 11 which were compared to the test of normal PCBN tools.



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surface roughness of the workpiece was measured with a WYKO N7910 optical profiler, all of which were compared to the test of normal PCBN tools.

Figure 3. The GCr15 workpiece. Figure 3. The GCr15 workpiece.

3. Analysis of Test Results 3. Analysis of Test Results According to the test scheme, the cutting tests were carried out. The surface roughness data of According to the testand scheme, the cutting tests out. surface roughness of GCr15 were measured analyzed. The effect ofwere microcarried textures onThe surface roughness was data obtained. Figure effect 3. The GCr15 GCr15 were measured and analyzed. The of workpiece. micro textures on surface roughness was obtained. 3.1. Surface 3.Roughness of Gcr15 Cut by Normal PCBN Tools Analysis of Test Results Figure 4 isAccording the of 3DGcr15 topography of the GCr15 cut bywere normal atroughness differentdata cutting speeds. to the test scheme, cutting tests carriedPCBN out. Thetools surface of 3.1. Surface Roughness Cut by Normal PCBN Tools GCr15 were measured and surface analyzed. of The effect of micro surface roughness was speed was The observation shows that the GCr15 was thetextures most on rough when cutting 4 obtained. is thewhile 3D topography of GCr15 cut by normal PCBN tools atvdifferent cutting speeds. v2 Figure = 72 m/min, the best surface morphology was obtained when 1 = 60 m/min. Randomly The observation shows that the surface of GCr15 was the most rough when cutting speed wascurves. v2 = selecting six for roughness 3.1.points Surface was Roughness of Gcr15 Cut bymeasurement, Normal PCBN Toolswhich obtained the surface roughness 72 Figure m/min, the best surface curve morphology was obtained when vtools. 1 = 60According m/min. Randomly 5 iswhile the surface GCr15 by normal PCBN to the curve Figure 4 isroughness the 3D topography ofofGCr15 cut cut by normal PCBN tools at different cutting speeds. selecting six points was for roughness measurement, which obtained the surface roughness The observation showsquality that the surface of GCr15 when was thecutting most rough whenwas cutting was v2 = curves. trend in Figure 5, the surface was optimal speed v1 =speed 60 m/min. However, m/min, whiletothe obtained when v1tools. = 60 m/min. Randomly Figure 5 isspeed the72surface roughness of morphology GCr15 cutwas by PCBN According to on thepressure curve cutting increased v2best = curve 72surface m/min, because thenormal effect of cutting force increasing selecting six points was for roughness measurement, which obtained the surface roughness curves. trend in Figure 5, the surface quality was optimal when cutting speed was v 1 = 60 m/min. However, and frictionFigure on the ofroughness GCr15 was serious. The heat and cutting temperature 5 is surface the surface curvemore of GCr15 cut by normal PCBN tools. According to the curve of cutting cutting speed increased 2 = 72 m/min, because the effect ofspeed, cutting force on during pressurethe process both increased. The reason is that, at this cutting the discharged trend in Figureto5, v the surface quality was optimal when cutting speed was v1 =heat 60 increasing m/min. However, and friction on theissurface of GCr15 more serious. The and cutting temperature of cutting cutting speed increased to =was 72heat m/min, because theresulting effectheat of cutting force increasing ontemperature pressure cutting process not as much asv2the generated, in a higher surface of the and friction onThe the surface of GCr15 wasat more serious. The heat and cutting temperature of cutting process both increased. reason is that, this cutting speed, the heat discharged during the workpiece, which leads to the rough of the surface. As the cutting speed increases to v3 = 85 m/min, process both increased. The reason is that, at this cutting speed, the heat discharged during the cutting process is not as much as the heat generated, resulting in a higher surface temperature of the heat is cutting increasingly degree of the workpiece is less process isdischarged, not as much asthe the hardened heat generated, resulting in a higher surface surface temperature of than the thecutting workpiece, leads to leads the rough of the surface. As thecutting cutting speed increases to 3 = 85 the which which to the rough of the surface. As force the speed increases to v3 = 85 speed vworkpiece, the surface stress and cutting of the machined surface arevreduced, 2 = 72 m/min, m/min, the heat is increasingly discharged, the hardened degree of the workpiece surface is less m/min, the heat is increasingly discharged, the hardened degree of the workpiece surface is less and the pressure and friction between the tool and the workpiece can also be reduced; consequently, than the cutting speed v 2 = 72 m/min, the surface stress and cutting force of the machined surface than cutting speed v2 = 72 m/min, the surfaceburrs stress and cutting force of the machined thethe surface quality is improved. In addition, the surface of machined Gcr15 havesurface a higher are reduced, and the pressure and frictionthe between theon tool and the workpiece can also be reduced; areheight reduced, and the pressure and friction between the tool and the workpiece can also be reduced; thanconsequently, other cutting speeds; Zhou that thetheheight ofthe burrs first the surface quality is pointed improved. out In addition, burrs on surface of increased machined and then consequently, the surface quality is improved. In addition, theburrs burrs on surface offirst machined Gcr15 a higher height than other cutting speeds; pointed out of that thethe height of burrs reduced with thehave increase of cutting speeds [19]. The Zhou surface the cutting workpiece were in increased and then reduced with the increase of cutting speeds [19]. The surface burrs of the cutting Gcr15 have a higher heighttheory than other cutting accordance with Zhou’s in this test. speeds; Zhou pointed out that the height of burrs first workpiece were in accordance with Zhou’s theory in this test. increased and then reduced with the increase of cutting speeds [19]. The surface burrs of the cutting workpiece were in accordance with Zhou’s theory in this test.


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(c) 4. The 3D topography GCr15 cutcut by normal PCBN tools at different speeds: (a) v1 = Figure 4. Figure The 3D topography ofofGCr15 by normal PCBN tools cutting at different cutting speeds: 60 m/min; (b) v2 = 72 m/min; (c) v3 = 85 m/min. (a) v1 = 60 m/min; (b) v2 = 72 m/min; (c) v3 = 85 m/min.

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Figure 4. The 3D topography of GCr15 cut by normal PCBN tools at different cutting speeds: (a) v1 = Figure 4. The 3D topography of GCr15 cut by normal PCBN tools at different cutting speeds: (a) v1 = Machines 2018, 5 of 11 = 72 m/min; (c) v3 = 85 m/min. 60 m/min; (b) v6,2 42 60 m/min; (b) v2 = 72 m/min; (c) v3 = 85 m/min.

Figure 5. Surface roughness curve of GCr15 cut by normal PCBN tools. Figure 5. Surface roughness curve of GCr15 cut by normal PCBN tools.

Figure 5.ofSurface roughness curve of GCr15 cut by normal PCBN tools. 3.2. Surface Roughness Gcr15 Cut by Vertical MicroGroove PCBN Tools 3.2. Surface Roughness of Gcr15 Cut by Vertical MicroGroove PCBN Tools Figure 6 is the 3D topography of GCr15 cut by vertical microgroove PCBN tools at different 3.2. Surface Roughness of Gcr15 Cut byofVertical MicroGroove PCBN Tools Figure 6 is the topography GCr15 cut by vertical microgroove at different cutting cutting speeds, and3D Figure 7 is the surface roughness curve of GCr15PCBN cut bytools vertical microgroove speeds,tools. Figure 7 is theof surface curvethere of GCr15 by vertical microgroove PCBN tools. PCBN The Figureroughness shows that were cut different degrees of PCBN serrated burrs on different Figure 6 isand the 3Danalysis topography of6 GCr15 cut by vertical microgroove tools at The analysis of Figure 6 shows that there were different degrees of serrated burrs on machined surfaces machined surfaces at different cutting speeds, of which the height of the surface burrs at v2 = 72 cutting speeds, and Figure 7 is the surface roughness curve of atGCr15 cut by vertical microgroove at different speeds, which the height the surface v2 = 72 m/min 60 m/min was cutting higher and the of roughness was moreofserious, andburrs the serrated burrs werewas lesshigher at v1 =and PCBN tools. The ofserious, Figure 6 shows that there were different degrees serrated burrs on the roughness and theFigure serrated were less at vthe m/min and vof 1 = 60 3 = 85 m/min and analysis v3 was = 85more m/min. Observing 7, burrs we can find that surface roughness at vm/min. 1 = 60 =height 60 m/min Observing 7,than we can the surfacehowever, roughness atthe v1cutting than that at machined surfaces at different cutting speeds, of which of was the surface burrs at v2 = 72 m/min was Figure smaller thatfind at vthat 3 = 85 m/min; when speed wassmaller v2 = 72 m/min, the v3 = 85 m/min; however, when cutting speed wasserious, v2 = 72was m/min, theserrated surface quality was thespeed worstat v1 = 60 surface quality was the roughness worst and thewas surface roughness highest. In the range of cutting m/min was higher and the more and the burrs were less and the surface roughness was highest. In the range of cutting speed set by tests, the height of serrated set byvtests, them/min. height ofObserving serrated burrs reached a maximum cutting v2 = 72 m/min, andat v1 = 60 m/min and 3 = 85 Figure 7, we can findat that thespeed surface roughness burrsdecreased reached a with maximum cutting increasing. speed v2 = 72 m/min, andof then decreased cuttingaffected speeds then cuttingat speeds The existence serrated burrswith seriously m/min was smaller than that at v 3 = 85 m/min; however, when cutting speed was v2 = 72 m/min, the increasing. The and existence of serrated seriously affected surface and also that the surface quality, also showed thatburrs the vertical microgrooves havequality, no inhibition onshowed serrated burrs surface of quality was the worst and the surface roughness was highest. In the range of cutting speed vertical microgrooves have no inhibition on serrated burrs of machined workpiece surface. machined workpiece surface.

set by tests, the height of serrated burrs reached a maximum at cutting speed v2 = 72 m/min, and then decreased with cutting speeds increasing. The existence of serrated burrs seriously affected surface quality, and also showed that the vertical microgrooves have no inhibition on serrated burrs of machined workpiece surface.


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(c) Figure 6. The 3D topography of GCr15 cut by vertical microgroove PCBN tools at different cutting 60m/min; m/min;(b) (b)v2v2= = m/min; = m/min. 85 m/min. 7272 m/min; (c)(c) v3 v=385 speeds: (a) v11 ==60

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Figure 6. The 3D topography of GCr15 cut by vertical microgroove PCBN tools at different cutting Figure 6. The 3D topography of GCr15 cut by vertical microgroove PCBN tools at different cutting6 of 11 Machines speeds: (a) 2018, v1 = 6,6042m/min; (b) v2 = 72 m/min; (c) v3 = 85 m/min. speeds: (a) v1 = 60 m/min; (b) v2 = 72 m/min; (c) v3 = 85 m/min.

Figure 7. Surface roughness curve of GCr15 cut by vertical microgroove PCBN tools. Figure 7. Surface roughness curve of GCr15 cut by vertical microgroove PCBN tools.

FigureRoughness 7. Surface of Microgroove GCr15 cut by vertical 3.3. Surface of roughness Gcr15 Cut bycurve Parallel PCBN Tools microgroove PCBN tools. 3.3. Surface Roughness of Gcr15 Cut by Parallel Microgroove PCBN Tools Figure 8 is the 3D topography of GCr15 cut by parallel microgroove PCBN tools at different 3.3. Surface Roughness of Cut by Microgroove PCBN Tools at PCBN Figure 8 isFigure theGcr15 3D8 topography of GCr15 cut by parallel microgroove at different cutting speeds. shows thatParallel the workpiece surface was rougher v1 = 60 tools m/min, and the cutting quality speeds.atFigure shows was that better. the workpiece surface was rougher at v1curve = 60 of m/min, and the surface v 3 = 858m/min Figure 9 is the surface roughness GCr15 cutat by different Figure 8 is the 3D topography of GCr15 cut by parallel microgroove PCBN tools surface quality at v = 85 m/min was better. Figure 9 is the surface roughness curve of GCr15 cut by 3 PCBN tools. It can be concluded that the surface roughness decreased with the parallel microgroove cutting speeds. Figure 8 shows that the workpiece surface was rougher at v 1 = 60 m/min, parallel microgroove PCBN tools. can be concluded thatthe the test surface roughness decreased the and the increase of cutting speed, whichIt was different from results of normal and with vertical surface microgroove quality atcutting vPCBN 3 = 85 m/min better. Figure 9 istest the surface roughness curve ofslower, GCr15 cut by increase of speed, which was different from results of normal and vertical microgroove tools. Thewas analysis shows that the the heat dissipation of cutting heat was PCBN tools. The analysis shows that the heat dissipation of cutting heat was slower, and the heat with the parallel and microgroove tools. Itsurface can bewas concluded surface roughness decreased the heat of PCBN the workpiece higher in that lowerthe speed. The surface temperature was ofof thecutting workpiece surface was higher lower speed. The surface temperature was higher the vertical and the plastic deformation ofin the surface metal was larger, which led to poor and surface increasehigher speed, which was different from the test results ofthenormal and plastic deformation of the surface metal was larger, which led to the poor surface quality. In higher quality. In higher speed cutting, most of the cutting heat on the surface was transmitted with the microgroove PCBN tools. The analysis shows that the heat dissipation of cutting heat was slower, speedand cutting, most body, of the cutting on the surface transmitted with the chip andthe the process knife body, chip the knife and theheat workpiece surfacewas also became hardened during of and themachining, heat of the workpiece surface was higher in lower speed. The surface temperature was and the workpiece surfacealso alsoaffect became hardened during the process ofthree machining, which would 8, also which would surface quality. Compared to the diagrams of Figure it higher and the plastic of the the metal was larger, ledwhich to machined the poor surface affect surface Compared to diagrams of Figure 8, itserrated waswhich found that the was found thatquality. thedeformation machined surface at three vsurface 1 = 60 m/min had slightly burrs, showed surface v1 speed = 60 m/min had slightly serrated burrs,towhich the lower cutting waswith the quality. that In higher cutting, mostnot of the cutting heatshowed on thethat surface was transmitted the atlower cutting speed was conducive better surface quality when 40 µmspeed parallel not conducive to better surface quality when 40 µm parallel microgroove PCBN tools cut GCr15. microgroove GCr15. chip and the knifePCBN body,tools andcutthe workpiece surface also became hardened during the process of

machining, which would also affect surface quality. Compared to the three diagrams of Figure 8, it was found that the machined surface at v1 = 60 m/min had slightly serrated burrs, which showed that the lower cutting speed was not conducive to better surface quality when 40 µm parallel microgroove PCBN tools cut GCr15.


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(c) Figure 8. The 3D topography of GCr15 cut by parallel microgroove PCBN tools at different cutting 60m/min; m/min;(b) (b)v2v2= = m/min; = m/min. 85 m/min. 7272 m/min; (c)(c) v3 v=385 speeds: (a) v11 ==60

(c) Figure 8. The 3D topography of GCr15 cut by parallel microgroove PCBN tools at different cutting (c) Machines 2018, 6, 42 7 of 11 speeds: (a) v1 = 60 m/min; (b) v2 = 72 m/min; (c) v3 = 85 m/min. Figure 8. The 3D topography of GCr15 cut by parallel microgroove PCBN tools at different cutting speeds: (a) v1 = 60 m/min; (b) v2 = 72 m/min; (c) v3 = 85 m/min.

Figure 9. 9. Surface roughness curve ofof GCr15 cut byby parallel microgroove Figure Surface roughness curve GCr15 cut parallel microgroovePCBN PCBNtools. tools.

Figure 9. Surface roughness curve of GCr15 cut by parallel microgroove PCBN tools. 3.4.Surface Surface RoughnessofofGcr15 Gcr15Cut CutbybyMicrohole MicroholePCBN PCBNTools Tools 3.4. Roughness

3.4. Surface Figure Roughness Cut by Microhole PCBN Tools Figure10 10isis of theGcr15 3D cut by by microhole PCBN toolstools at different cutting speeds. the 3D topography topographyofofGCr15 GCr15 cut microhole PCBN at different cutting When cutting speed was v = 85 m/min, surface quality was relatively rougher, while the surface

speeds.10When cutting speed3 was v3 =of 85 GCr15 m/min, surface was relatively the cutting Figure is the 3D topography cut byquality microhole PCBN rougher, tools atwhile different topography at v2 = at 72vm/min was smoother. Figure 11 is the11surface curve of GCr15 cut surface topography 2 = 72 m/min was smoother. Figure is the roughness surface roughness curve of speeds. When cutting speed was v3 = 85 m/min, surface quality was relatively rougher, while the by microhole PCBN tools. Observing the surface roughness curve of GCr15 cut by diameter 120 µm GCr15 cut by microhole PCBN tools. Observing the surface roughness curve of GCr15 cut by surfacediameter topography v2 = 72 m/min was smoother. Figure 11 that is the surface roughness microhole tools inmicrohole Figure 11,tools it canin beFigure concluded roughness of GCr15 was the largest 120 µmat 11, itthat canthe besurface concluded the surface roughness ofatcurve of v3 = by 85 m/min, and the value v1 = 60 m/min was at greater than thatcurve of v2greater = of 72 m/min. GCr15 GCr15 cut microhole PCBN Observing the surface GCr15 cut by was the largest at vroughness 3 = 85 tools. m/min, andatthe roughness value vroughness 1 = 60 m/min was than At the same time, it can be seen from Figure 10 that there was not a large number of serrated burrs on that120 of vµm 2 = 72microhole m/min. At the same it can Figure 10 that there not a large diameter tools in time, Figure 11,beitseen can from be concluded that thewas surface roughness of the machined surface turned by microhole PCBN tools, which was differentPCBN from normal PCBNwas tools, number of serrated burrs on the machined surface turned by microhole tools, which GCr15 was the largest at v3 = 85 m/min, and the roughness value at v1 = 60 m/min was greater than vertical from microgroove parallel microgroove PCBN tools. Consequently, microhole different normal PCBN PCBN tools, tools,and vertical microgroove PCBN tools, and parallel microgroove that of vtextures 2 = 72 m/min. At the same time, it can be seen from Figure 10 that there was not a large had the effect of inhibiting the serrated burrs. PCBN tools. Consequently, microhole textures had the effect of inhibiting the serrated burrs. number of serrated burrs on the machined surface turned by microhole PCBN tools, which was different from normal PCBN tools, vertical microgroove PCBN tools, and parallel microgroove PCBN tools. Consequently, microhole textures had the effect of inhibiting the serrated burrs.


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(c) The3D 3Dtopography topographyofofGCr15 GCr15cut cut microhole PCBN tools at different cutting speeds: Figure 10. The byby microhole PCBN tools at different cutting speeds: (a) (a) = 60 m/min; (b) v = 72 m/min; (c) v = 85 m/min. m/min; (b) v 2 = 72 m/min; (c) v 3 = 85 m/min. v1 =v60 1 2 3

(c) (c) Figure 10. The 3D topography of GCr15 cut by microhole PCBN tools at different cutting speeds: (a) 10. The 3D topography of GCr15 cut by microhole PCBN tools at different cutting speeds: (a) 1 = 60 m/min; vFigure Machines 2018, 6, 42 (b) v2 = 72 m/min; (c) v3 = 85 m/min. 8 of 11 v1 = 60 m/min; (b) v2 = 72 m/min; (c) v3 = 85 m/min.

Figure 11. Surface roughness curve of GCr15 cut by microhole PCBN tools. Figure Figure 11. 11. Surface Surface roughness roughness curve curve of of GCr15 GCr15 cut cut by by microhole microhole PCBN PCBN tools. tools.

4. Analysis Speeds 4. Analysis of of Surface Surface Roughness Roughness at at Different Different Speeds 4. Analysis of Surface Roughness at Different Speeds Figure 12 different PCBN tools at at v1 Figure 12 is is the the comparison comparisonof ofthe thesurface surfaceroughness roughnessofofGCr15 GCr15cut cutbyby different PCBN tools Figure According 12 is the comparison of the surface roughness of GCr15 cut byroughness different PCBN tools atby v1 = 60 m/min. to the curve distribution in Figure 12, the surface of GCr15 cut v1 = 60 m/min. According to the curve distribution in Figure 12, the surface roughness of GCr15 cut by = 60 m/min. According to the curve distribution in Figure 12, the surface roughness of GCr15 cut by parallel microgroove microgroovePCBN PCBNtools toolswas was largest, surface roughness cutmicrohole by microhole parallel thethe largest, thethe surface roughness cut by PCBNPCBN tools parallel microgroove PCBN tools was the largest, the surface microgroove roughness cut by microhole PCBN tools was minimum, and the surface roughness cut by vertical PCBN tools lower was minimum, and the surface roughness cut by vertical microgroove PCBN tools was lowerwas than that tools that was minimum, and thetools. surface roughness cut by vertical microgroove PCBN tools lower than normal PCBN It can be judged parallel micro were notwas good for of normal of PCBN tools. It can be judged that parallelthat micro grooves weregrooves not good for good surface than that of normal PCBN tools. It can be judged that parallel micro grooves were not good for good surface quality compared tools at v1 = 60 m/min, while microholes and vertical quality compared to normal tools to at vnormal 1 = 60 m/min, while microholes and vertical microgrooves had good surface had quality compared to normal tools at v1 = 60 m/min, while microholes and vertical microgrooves thesurface effect ofroughness. reducing surface roughness. the effect of reducing microgrooves had the effect of reducing surface roughness.

Figure The comparison comparison of of the the surface surface roughness roughness of of GCr15 GCr15 cut cut by by different different PCBN PCBN tools Figure 12. 12. The tools at at vvFigure 60 m/min. m/min. 11 == 60 12. The comparison of the surface roughness of GCr15 cut by different PCBN tools at v1 = 60 m/min.

Figure 13 is the comparison of the surface roughness of GCr15 cut by different PCBN tools at Figure 13 is the comparison of the surface roughness of GCr15 cut by different PCBN tools at v2 v2 = 72 m/min. Through the analysis of Figure 13, it was found that the surface roughness of the is the comparison of the roughness GCr15 cutthe by surface differentroughness PCBN tools v2 = 72 Figure m/min.13Through the analysis of surface Figure 13, it was of found that ofatthe workpiece machined by vertical-groove tools was higher than that of other tools, and the surface = 72 m/min. Throughbythe analysis of Figure 13, ithigher was found thatofthe surface of the workpiece machined vertical-groove tools was than that other tools,roughness and the surface quality was the worst after cutting. The surface roughness of microhole tools was still the smallest after workpiece machined by vertical-groove tools was higher than that of other andthe thesmallest surface quality the worst after cutting. The surface roughness of microhole toolstools, was still Machines 2018, 6, xwas FOR PEER REVIEW cutting. The surface roughness of non-textured tools was also lower than that of parallel-groove tools. qualitycutting. was theThe worstsurface after cutting. The surface roughness of microhole tools lower was still the smallest after roughness of non-textured tools was also than that of after cutting. The surface roughness of non-textured tools was also lower than that of parallel-groove tools. parallel-groove tools.

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Figure 13. The comparison of the surface roughness of GCr15 cut by different PCBN tools at Figure 13. The comparison of the surface roughness of GCr15 cut by different PCBN tools at v2 = 72 v2 = 72 m/min. m/min.

Figure 14 is the comparison of the surface roughness of GCr15 cut by different PCBN tools at v3 = 85 m/min. Analyzing Figure 14, it was found that on the contrast of micro-texture tools,


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the maximum surface roughness of GCr15 was produced by parallel microgroove PCBN tools, followed by vertical microgroove PCBN tools, and the surface roughness was minimized by microhole PCBN tools. By calculating the average of the surface roughness, we found that the average roughness of GCr15 cut by normal PCBN tools was 1.79 µm, the average roughness of GCr15 cut by vertical microgroove PCBN tools was 1.74 µm, while the mean value of GCr15 cut by microhole tools was only Figure 1.71 µm. cancomparison be seen that micro holesroughness and vertical microcut grooves are favorable forat reducing 13.ItThe of the surface of GCr15 by different PCBN tools v2 = 72 the surface roughness of GCr15 at v3 = 85 m/min. m/min.

Figure 14. 14. The Thecomparison comparison surface roughness of GCr15 cut by different at Figure of of thethe surface roughness of GCr15 cut by different PCBNPCBN tools attools v3 = 85 v = 85 m/min. 3 m/min.

5. Conclusions Figure 14 is the comparison of the surface roughness of GCr15 cut by different PCBN tools at v3 comparison and analysis, was found that, experimental cutting speeds, = 85 Through m/min. Analyzing Figure 14, it wasitfound that on the under contrast of micro-texture tools, the compared to normal PCBN tools, the surface roughness of GCr15 obtained by parallel microgroove maximum surface roughness of GCr15 was produced by parallel microgroove PCBN tools, PCBN tools larger, and parallel microgroove PCBN machine good surface quality. In by all followed byis vertical microgroove PCBN tools, andtools the can’t surface roughness was minimized tools, the surface by microhole PCBN was the roughness, smallest. Thewe surface microhole PCBNroughness tools. Byobtained calculating the average of tools the surface foundroughness that the obtained by verticalof microgroove was only larger than that of normal at v2 roughness = 72 m/min, average roughness GCr15 cut tools by normal PCBN tools was 1.79 µm, thetools average of but wascut less other cutting speeds.PCBN From analyzing the type micro textures, the microhole GCr15 byatvertical microgroove tools was 1.74 µm,of while the mean value of GCr15texture cut by was more conducive to the1.71 discharge of the heat, andholes the heat the cutting was not microhole tools was only µm. It can be cutting seen that micro andof vertical microarea grooves are enough make the workpiece surface seriously deformed; favorabletofor reducing the surface roughness of GCr15 at v3 = therefore, 85 m/min.the surface quality of GCr15 was better. The cutting temperature of the vertical microgroove texture was lower than that of parallel 5. Conclusions microgroove texture; moreover, the vertical microgroove texture was parallel to outflow direction of chips, which can greatly reduce the friction between rake face and chip, so vertical microgroove texture Through comparison and analysis, it was found that, under experimental cutting speeds, is favorable for discharging cutting heat. However, a certain angle was formed between the parallel compared to normal PCBN tools, the surface roughness of GCr15 obtained by parallel microgroove microgroove texture and the chip outflow direction, and the chip outflows will have friction with the PCBN tools is larger, and parallel microgroove PCBN tools can’t machine good surface quality. In parallel microgroove texture, which causes a relatively high cutting temperature and a relatively large all tools, the surface roughness obtained by microhole PCBN tools was the smallest. The surface deformation degree of workpiece surface; therefore, a parallel microgroove texture is not good for roughness obtained by vertical microgroove tools was only larger than that of normal tools at v2 = obtaining good surface quality. The results of this test are as follow: 72 m/min, but was less at other cutting speeds. From analyzing the type of micro textures, the microhole texture was more conducive to thetexture discharge of the heat, the heat of the (1). Compared to normal tools, the microhole was the mostcutting beneficial to and reducing the surface cutting area wasofnot enough and to make the workpiece surface seriously deformed; therefore, the roughness workpiece, the vertical microgroove texture was second, while the parallel surface quality of GCr15 was better. The cutting temperature of the vertical microgroove texture microgroove texture increased the roughness. was lower of parallel microgroove texture; moreover, them/min, verticalthemicrogroove texture (2). When than 30 µmthat vertical microgroove tools turned GCr15 at v2 = 72 surface quality was was parallel to outflow direction of chips, which can greatly reduce the friction between rake face poor due to serrated burrs on workpiece surface, and the surface roughness of the workpiece and chip, so vertical microgroove is favorable for lower discharging cutting heat. However, a was small at v1 = 60 m/min andtexture v3 = 85 m/min, because speed and higher speed were able certain thetoparallel texture and the chip outflow direction, to angle inhibitwas the formed serratedbetween burrs and producemicrogroove better surface quality. and the chip outflows will have friction with the parallel microgroove texture, with which a (3). The surface roughness obtained by 40 µm parallel microgroove tools decreased thecauses increase relatively high cutting temperature and a relatively large deformation degree of workpiece surface; of cutting speed, but was still larger than that of normal PCBN tools. therefore, a parallel microgroove texture is nottools goodwas forbest obtaining good surface quality. The texture results (4). The surface quality obtained by microhole in all cutting tests, and microhole of thishad testa are as follow: certain inhibitory effect on serrated burrs. In this paper, the experimental results achieved certain good results, which expands the application of micro textures, because previous research applied only more micro-texture methods


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in cemented carbide tools, but this method is used in PCBN tools in this paper. At the same time, this paper has played a role in promoting the application of micro-texture tools in engineering. Author Contributions: C.P. conceived and designed the experiments, and made data curation, formal analysis, methodology, project administration, and writing-original draft; Q.L. gave the conceptualization, funding acquisition, resources, and writing-review and editing; K.H. made the project administration, software, and writing-original draft; Y.J. made the software, supervision, and data curation; Y.S. provided resources, software, and made supervision. Funding: This research received no external funding. Acknowledgments: Thanks Changchun University for providing test equipment and related measuring equipment. Thanks teacher for your instruction. Thanks other authors for your services. Conflicts of Interest: There is no conflict of interests between all authors.

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