Surface Modification of High Chrome Steel by Laser Surface Melting
Laser surface melting has been performed on high chrome steels by a 5kW CW CO2 laser using different overlapping ratios. The microstructures of laser melted steels were analysed by SEM and the hardness profiles were determined by a Vickers hardness tester. The corrosion characteristics of laser melted steels in 3.5% NaCl solution were studied by electrochemical corrosion equipment. The melted zone of a single laser track exhibits a mixed structure of dendritic, cellular and equiaxed austenite while the overlapped melted zone is only composed of austenitic dendrites. Using a large overlapping ratio (OR) gives a more uniform hardened-depth. The microhardness with an OR of 33.3% is higher compared to 16.7% and 50%. The corrosion resistance of laser melted steel is improved arising from the dissolution of carbides, the increasing of alloying elements in the solid solution and the large amount of austenite. Among all the studied specimens the one, which is laser treated with 33.3% OR presents the better corrosion resistance.
Dongming Guo, Jun Wang, Zhenyuan Jia, Renke Kang, Hang Gao, and Xuyue Wang
M.Y. Li et al., "Surface Modification of High Chrome Steel by Laser Surface Melting", Materials Science Forum, Vols. 628-629, pp. 673-678, 2009