Effects of heat treatment on the nano-indentation, corrosion and cavitation erosion behavior of 17-4PH stainless steel by laser surface melting.

The effects of heat treatment on the microstructure, residual stresses, nano-indentation behavior, the resistance to the corrosion and cavitation erosion (CE) of 17-4PH stainless steel (17-4PH SS) by laser surface melting (LSM) were thoroughly investigated. Experimental results showed that the samples were mainly composed of martensite phase, and the NbC precipitations formed after heat treatment. The distribution of NbC precipitations was more uniform in the sample (S3) after solution treatment 3 h at 1040 °C + aging treatment 3 h at 480 °C. The grain size was increased for the samples after heat treatment. This heat treatment processing significantly reduced the residual stresses generated from the LSM process, and the nano-indentation behavior of the LSM samples after heat treatment was improved compared to that of the LSM sample without heat treatment. The S3 sample displayed the highest corrosion resistance as indicated by the low corrosion current density (i corr), high pitting potential (E pit) and high polarization resistance (R p). The CE resistance of samples after heat treatment in 3.5 wt% NaCl solution was higher than that of the sample without heat treatment. Among them, the S3 sample exhibited the highest CE resistance, and its CE mass loss was only 59.5 % of the sample without heat treatment. The excellent CE resistance resulted from the appropriate combination of mechanical properties, corrosion resistance and self-recovery ability of the passivation film. • 17-4PH stainless steel by laser surface melting was subjected to heat treatment. • The microstructure and residual stress of samples after heat treatment were studied. • The nano-indentation behaviors of samples after heat treatment were improved. • The resistance to corrosion and cavitation erosion was improved. [ABSTRACT FROM AUTHOR]