Effect of Laser-Induced Microstructure in Cavitation Erosion Performance of Martensitic Stainless Steel

Abstract

Cavitation erosion causes material removal from the surface of metal components submerged under swift flowing fluid due to implosions of gas bubbles on their surface. Since erosion is a surface degradation phenomenon, laser surface hardening can be a promising solution to tackle this problem without affecting the bulk properties of material. Laser acts as a localized surface heater which induces rapid non-equilibrium phase transformation and produces hard microstructure near the surface. In this paper, the effect of laser-induced microstructure on cavitation erosion performance of AISI 420 martensitic stainless steel is systematically investigated. Surface hardness as high as 700 HV is recorded after laser hardening and the microstructure consisted of fine carbides and retained austenite in a martensitic matrix. Such microstructure is attributed to result in high cavitation erosion resistance. The cavitation erosion resistance of laser hardened surface was found to be 18 times higher than that of untreated surface. The results indicate the significance of microstructural transformation induced by laser treatment on erosion performance of stainless steels.