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Effect of Laser Surface Hardening on the Microstructure, Hardness Wear Resistance and Softening of a Low Carbon Steel
P-L. Zhang, H. Yan, P-Q. Xu, Z-S. Yu, C-G. Li and Q-H. Lu

A study of the laser surface hardening process of low carbon steel has been carried out. A tiny lath martensite can be obtained in hardened zone and it can increase the hardness of steel surface. Laser hardening surface treatment can decrease the friction coefficient to improve the wear resistance of steel surface. Softening in overlapping passes by laser-overlapped scanning surface hardening is a difficult problem of laser surface modification. The effect of activation energy of diffusion for carbon atom in steel and heating rate of laser hardening on the decomposition of martensite have been investigated by a diffusion model based on the principle of carbon diffusion in martensite. The results indicated that activation energy for diffusion of carbon in steel plays a main role in hindering decomposition of carbide and increasing heating rate of lap scanning has a limited action in reducing temper softening during laser overlapping scanning.

Keywords: CO2 laser, laser hardening, microstructure, wear resistance, softening, overlapping zone, heating rate

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