Effects of Aging Treatments on the High-Temperature Wear Behavior of 60Nitinol Alloy

This study was undertaken to investigate the effect of heat treatments on the high-temperature wear behavior of 60Nitinol. The samples were hot-worked, aged at two temperatures of 400 and 700 degrees C for 1h and then water quenched. The microstructure of the alloys was investigated by scanning electron microscopy and X-ray diffraction. Sliding wear tests were performed at two temperatures of 25 and 200 degrees C using three types of 60Nitinol disks: hot-worked, aged at 400 degrees C, and aged at 700 degrees C. All wear tests were performed at a speed of 0.3m/s under a normal load of 60N for a total sliding distance of 1,000m using WC-Co pins sliding against 60Nitinol disks. The worn surfaces and microstructure of the subsurfaces were studied by scanning electron microscopy. Compression and hardness tests were also performed to characterize the mechanical properties of the alloys. The highest fracture strain and lowest hardness were obtained for the sample aged at 700 degrees C that contained Ni3Ti2 precipitants. This sample also showed the maximum wear resistance at a wear testing temperature of 200 degrees C. This was attributed to the formation of a more compact and stable tribological layer on the worn surface of the softer sample.