The Effect of Hot Rolling Temperature on the Wear Properties of NiTi Rods

The effect of the hot rolling process on the wear properties of NiTi rods was investigated in this study. 10-mm diameter NiTi rods were rolled down to 5 mm in diameter, corresponding to 75% area reduction. The hot rolling process was conducted at different temperatures changing from 650 to 900 degrees C. After the hot rolling process was completed, the rods were tested using a pin-on-disk set-up to examine the wear properties. The friction coefficient and the specific wear rate were calculated for each rod. In addition to the wear tests, the macro-hardness of each rod was measured. Furthermore, X-ray, FESEM and EDS analyses were performed to visualize the worn surfaces. The hardness of the as-received sample was 60,5 HRA. It was observed that hardness increased after the hot rolling process. In particular, samples which were hot rolled at 700 degrees C and 900 degrees C showed similar to 10% increase in hardness according to as-received sample. The highest volume loss for all sliding distances occurred on the as-received sample. Also, as expected, the second-highest volume loss occurred in the sample rolled at 650 degrees C, due to the relation between hardness and volume loss. The wear behavior including surface adhesion may be affected by the hardening and the softening mechanisms happening during the hot rolling process.