Microstructure and Wear Resistance Enhancement of Semi-Steel Rolls by Laser Surface Alloying of NiCr-Cr3C2
G. Sun, Y. Zhang, C. Liu, P. Li and X. Tao
Laser surface alloying was used to form wear resistant layers on semisteel rolls with NiCr-Cr3C2 powders. Microstructure, element distribution, phases, microhardness distribution and wear behaviour of the layers were investigated. Observed dendrites and eutectics in the layers were found to be composed of austenite, martensite and carbides, austenite, martensite, respectively. The microhardness of the alloyed layers was lower than that of the substrate owing to the large fraction of the retained austenite. Wear results at ambient and 500◦C indicate that the wear mass loss of the substrate was 2.2 and 4.9 times that of specimens with pre-layers of 30 and 18 mm in thickness, respectively. The improvement in wear resistance is believed to be the effect of the high toughness of the retained austenite, austenite-martensite transformation and the oxide films which can offer better tribological enhancement at high temperatures.
Keywords: laser surface alloying, semi-steel roll, carbide, microstructure, microhardness, wear