Available online at www.sciencedirect.com
Physics Procedia 25 (2012) 200 – 204
2012 International Conference on Solid State Devices and Materials Science
Research on Microstructure and Property of Fe-VC Composite Material Made by Laser Cladding Wei Zhanga,a* a
Mechanical Engineering Branch Institute, Zhejiang Institute of Mechanical & Electrical Engineering, Hangzhou 310053, China
Abstract The experiment of laser cladding on the surface of H13 steel was made. Vanadium carbide (VC) powder and Fe-base alloy powder were used as cladding material. The microstructure and property of laser cladding layer were studied. The research showed that laser cladding layer had better properties such as minute crystals, deeper layer, higher hardness and good metallurgical bonding with base metal. The average hardness of cladding zone was 900HV0.2. The average hardness of cladding layer increased five times than that of base material. H13 steel was widely used in the field of hot dies. Using laser cladding, the good wear layer would greatly increase the mold useful life.
© 2012 2011 Published Published by by Elsevier Elsevier B.V. Ltd. Selection organizer] © Selection and/or and/or peer-review peer-review under under responsibility responsibility of of [name Garry Lee Open access under CC BY-NC-ND license. Keywords: Laser Cladding; Microstructure; Property; Nickel Alloy; Tungsten Carbide
1. Introduction H13 steel (4Cr5MoSiV1) was one kind of hot die steel. It had been widely used in the manufacturing of hot-working die and pressure-casting die [1-2]. Because of bad running conditions, these parts would easily wear. The hardness of quenched and tempered H13 steel was not hard enough to resist washing and abrading. To precise hot die, the lower hardness would greatly decrease the life length and part precision. So, precise hot die should be strengthened. The traditional mould strengthening methods were not suitable because of some defect [3]. For example, carburizing and nitriding were sensitive with the type of steel. Besides, depth of carburizing layer and nitriding layer were very thin. Thermal spraying and build-up welding were bad bonding with base material. The structure of hot die was very complex. The traditional
* Corresponding author. Tel.: +86-0571-87772613; fax: +86-0571-87772611. E-mail address:
[email protected].
1875-3892 © 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of Garry Lee Open access under CC BY-NC-ND license. doi:10.1016/j.phpro.2012.03.071
201
Wei Zhang / Physics Procedia 25 (2012) 200 – 204
heat treatment, such as quenching, normalizing would easily lead to cracking and deforming. Laser cladding was a new method of surface modification. Because of the characteristic of high controllability, high precision, low deformation and metallurgical bonding between cladding layer and substrate, laser cladding has greatly application value in the field of mould strengthening [4-5]. 2. Material and methods The primary experimental equipment included 10kW CO2 laser process system, numerical control machine, HXS-1000AY sclerometer, Nikon metallographic microscope. Argon was used as shielding gas. The experiments were done with laser scanning speed of 500mm/min, laser power of 6kW, laser beam diameter of 5mm. VC powder and Fe-base alloy powder were used as cladding material. The substrate was H13 steel which was annealed. The chemical composition of H13 steel was shown by Table 1. The chemical composition of Fe-base alloy powder was shown by Table 2. Table 1. Chemical composition of H13 steel (wt%) Element
C
Si
Cr
Mn
Mo
V
Fe
Wt%
0.30
0.80
4.70
0.20
1.10
0.80
Bal.
Table 2. Chemical composition of Fe-base alloy powder (wt%) Element
C
Cr
Si
Mn
Mo
Fe
Wt%
0.40
5.60
2.50
1.30
2.86
Bal.
3. Microstructure Fig.1 was the microstructure of cross-section of laser cladding specimen. Base on the difference of structure style and position, the cross-section could be divided into five zone, upper cladding layer, middle cladding layer, bonding zone, hardening (heat-affected) zone and matrix. Fig.1a was the high magnified microstructure of upper cladding layer. Fig.1b was the microscopic image of middle cladding layer. The spectral energy distribution of cladding layer was shown in Fig.2. The chemical composition of basal phase was shown in Table 3. From Fig.2 and Table 3, we could find that the structure of cladding layer was Fe-base over-saturation solid solution with the solute elements of V, Cr, Mo, et al. Besides, there were some network carbide (Fe3c) and superfine carbide particles (VC). The number of superfine carbide particles on the top of cladding layer was more than that of middle cladding layer. This was because the cooling velocity of upper cladding was much lower than that of middle cladding layer. The bonding zone and hardening zone were shown in Fig.1c. There was good metallurgical bonding between cladding layer with base metal. There were no cracking and blow hole. Fig.1d was high magnified image of matrix, which was hypoeutectoid structure (ferrite + perlite).
202
Wei Zhang / Physics Procedia 25 (2012) 200 – 204
(a)
(b)
10ʅm
10ʅm
(c)
(d)
20ʅm
100ʅm
Fig.1. Microstructure of cross-section of laser cladding specimen (a) upper cladding layer; (b) middle cladding layer; (c) bonding pad and heat-affected zone; (d) matrix
Fig.2. Spectral energy distribution of base-phase
203
Wei Zhang / Physics Procedia 25 (2012) 200 – 204 Table 3. Chemical composition of grain (wt%) Element
Atom %
Element Wt %
C
21.88
6.07
O
5.32
1.97
Al
0.42
0.26
Si
1.27
0.82
V
9.09
10.70
Cr
4.39
5.28
Mn
0.47
0.60
Fe
56.56
72.98
Mo
0.60
1.32
Total
100.00
100.00
4. Microhardness The hardness distribution curve of cladding specimen was shown in Fig.3. The average hardness of cladding layer (0-1.2mm) was about 900HV0.2. The average hardness of cladding increased 3.5 times than that of base metal. The hardness of hardening zone (1.2-2.5mm) was gradient descent from 852HV0.2 to 208HV0.2. The hardness distribution was consistent with metallurgical structure. 900
Hardness/HV0.2
800 700 600 500 400 300 200 100 0.0
0.5
1.0
1.5
Fig.3. Microhardness distribution curves of laser cladding specimen
2.0
2.5
3.0
3.5
Depth/mm
204
Wei Zhang / Physics Procedia 25 (2012) 200 – 204
5. Conclusions The experiment of laser cladding Fe-VC composite powder on the surface of H13 steel was made. Research results showed that the laser cladding layer was compact and had no cracks. The cladding layer exhibited the structure of Fe-base over-saturation solid solution with network carbide and dispersing superfine carbide particles. The average hardness of cladding layer was 900HV0.2. The property of laser cladding was more controllable and would generate great economy efficiency in the field of hot dies strengthening.
Acknowledgements The authors would like to appreciate financial support from the scientific research projects fund from the education department of Zhejiang province (Y201120211).
References [1] Chen QL, Yang AJ, Zheng KA, et al. Failure analysis of die- casting die. Shanghai Metals 1999;21:25-35. [2]Wang M, Liu ZD, Bao ZJ. Study on failure mechanism of H13 steel hot-forging dies for automobile. Forging & Stamping Technology 2008; 33:47-48. [3] Zhang W, Yao JH. Research of repairing the abraded shafts using laser overlaying welding technology. Applied Laser 2004; 24:342-344. [4] Zhang D, Shan JG, Ren JL. Status and development of cladding with high power density beam. Laser Technology 2001; 25: 39-42. [5] Zhang QM, Liu XM, Sun N, et al. Investigation on microstructure and properties of broad-beam laser overlapping cladding F305 formed by powder feeding method. Heat Treatment of Metals 2001;4 :13-18.
