Surface and structural characteristics of cast NiTi alloy impacted by submerged cavitating waterjet

Abstract

The NiTi alloy has great application potential in the engineering fields involving cavitation. The present study aims to reveal variations in surface and structure characteristics of the NiTi alloy subjected to submerged waterjet. Effects of the standoff distance and cavitation treatment duration were investigated. The volume loss, microstructure, phase transition temperature, and cross-sectional hardness were comprehensive analyzed. The results indicate that reduced standoff distance and prolonged waterjet exposure time result in increased cumulative volume loss and surface roughness of the NiTi alloy specimens. Cavitation imposes a significant thermal effect on the NiTi alloy. A 120-min cavitation treatment induces a hardened layer of approximately 200 µm in depth. The increase in microhardness of surface layer is closely related to dislocation strengthening and grain refinement. Compared to 316L stainless steel, the NiTi alloy exhibits higher resistance to cavitation, which is attributed to the existence of a large amount of twinning and high reversibility of phase transformation. The obtained conclusions are expected to shed light on the response of NiTi alloy to cavitation treatment and the mechanism of waterjet cavitation, providing a reference for application of NiTi alloys in engineering fields involving cavitation.