Relationship between microstructure of laser alloyed C45 steel and its cavitation resistance

The laser surface alloying of carbon steel (0.45 wt.% C) with Mn, Ni, Cr, Nb, Mo, and Co was carried out by 6 kW cw CO2 laser. The microstructure, chemical composition and phase identification of the modified layer were examined using scanning electron microscopy, light microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry, respectively. Cavitation behaviour of produced layers was investigated in a rotating disc facility. Cavitation properties of laser processed steel were calculated in the initial stage of erosion, on the surface of about 4 mm2, on which cavitation intensity was constant. Among properties characterising the cavitation erosion resistance of materials were proposed such as stress intensity factor of strengthened surface layer and resistance of surface to plastic deformation under cavitation loading. It was found that better resistance was achieved if steel microstructures were susceptible to strain hardening due to presence of some amount of austenite.