Water assisted fiber laser machining for NiTiCuHfZr shape memory alloy

Shape memory alloys (SMAs) based on nickel-titanium (NiTi) are highly temperature-sensitive, laser beam machining causes heat-affected zones (HAZ), residual stress, and microstructural changes. The addition of elements such as Zr, Cu and Hf can improve the thermomechanical properties of NiTi SMAs, thereby tailoring transformation characteristics and stabilizing the phase. These features are especially important for aircraft parts, sensors and medical components. Due to high heat input, traditional fiber laser machining of quinary NiTiCuHfZr SMAs produces significant thermal damage. The innovative hybrid machining process, water-assisted fiber laser cutting (WJ-FLC), uses laser machining with a high-pressure water jet to improve heat dissipation. This study examined the key process factors that influence the surface properties of the quinary NiTiCuHfZr SMA. The RSM based on the Box–Behnken Design (RSM-BBD) was used to identify the suitable machining variables. The experimental results indicate that surface roughness has been reduced by 53.45% by lowering laser power and gas pressure. Similarly, MRR has increased by 40.1% due to higher laser power and gas pressure. The WJ-FLC may reduce the heat-affected zone by removing heat from the machined surface region. This was validated by the DSC analysis, which shows that optimal machining variables do not affect the SMA properties.