Comparing Surface Characteristics of Additively Manufactured and Cold Rolled NiTi Workpieces, Post - Processed Using Wire Electric Discharge Machining

This work investigated the resulting surface properties of additively manufactured (AM) NiTi samples compared to cold-rolled (CR) NiTi samples post-processed under a range of wire electric discharge machining (WEDM) settings. The research aimed to optimize surface topography and composition to enhance the surface properties and fatigue life of AM NiTi shape memory alloy components, focusing on minimizing the WEDM processing required for net-shape flat surfaces produced via AM. The intent is to reduce the overall material use and processing time for shape memory alloy AM components. In this study, the mean surface roughness (Ra) of the as-printed NiTi samples saw a 24% to 61% reduction, with the best Ra achieved being 4.23µm, down from 10.71µm. The WEDM processed AM sample surfaces had a 31% to 177% higher Ra than the CR equivalent samples. The material removal rate (MRR) aligned to within (at best) a 4% difference in the MRR between the AM sample and CR equivalent. Changes in the samples Vickers hardness (HV) presented a decrease of 1% to 29% on the CR samples and 3% to 38% on the AM samples, with the maximum decrease being 91.5HV and 136HV, respectively. These results highlight notable differences in machinability between CR and AM NiTi samples, emphasizing the need for further research to optimize WEDM processes for net-shape AM NiTi components.