Microstructure and wear resistance enhancement of cast steel rolls by laser surface alloying NiCr–Cr3C2

The laser surface alloying technique was used to form wear resistant layers on 70MnV cast steel rolls with NiCr–Cr3C2 powders. The objective was to investigate the effects of the scanning speed on microstructure, phases, microhardness and wear resistance. Results indicate that the alloyed layers had dense, pore and crack free and homogeneous structures, as well as a metallurgical bonding with the substrates. With the increase of scanning speed, volume of retained austenite in the alloyed layer increased, microhardness and wear resistance increased and the microstructure refined. Wear results indicated that the wear resistance of the alloyed layer was enhanced by 7.8 times compared with that of the cast steel substrate. The improvement in wear resistance was attributed to the combined results of the grain refining effect, the solution strengthening effect, the tough γ-Fe matrix of the layer, the distribution of the hard Cr7C3, Fe3C and martensite phases, and the good bonding between these hard phases and the matrix.