Wear and corrosion behavior of nano carbide dispersed AISI304 stainless steel by laser surface processing

Abstract

In this study, dispersion of tungsten carbide on AISI 304 stainless steel substrate has been carried out by laser melting of the sand blasted substrate using a 5 kW continuous wave (CW) Nd:YAG laser (with the beam diameter of 3 mm) with an output power ranging from 1.5–2 kW, and scan speed varying from 12 to 16 mm s−1 and simultaneous feeding of premixed WC + Co powders in the ratio (wt) of 1:4 (with a flow rate of 10 mg s−1). The microstructure of the composite zone is dendritic or cellular in morphology and consists of nano-tungsten carbide (both WC and W2C) and M23C6 precipitates. There is an enhancement in hardness due to carbide dispersion from 220 VHN of the as-received substrate to 290–400 VHN. The wear resistance is improved significantly with a maximum enhancement observed in the sample processed with an applied power of 2 kW and a scan speed of 12 mm s−1. The corrosion rate in a 3.56 wt% NaCl solution is significantly reduced due to laser processing in most samples except when processed with 2.5 kW applied power and 12 mm s−1 scan speed. However, pitting corrosion resistance is found to be improved (shifting of Epit towards noble direction) for the sample processed with an applied power of 2 kW and a scan speed of 12 mm s−1.