Effect of NiTi Addition on the Wear Resistance of YSZ Coatings

In this study, small fraction of NiTi (5 wt%) was added to Yttria stabilized zirconia (YSZ) top coat to improve it sliding wear resistance. The measurement of width of wear tracks after wear tests under a 15 N load for 100 m sliding distances showed that the width of wear track in NiTi-YSZ coating is shorter than that in YSZ coating which depicts the higher wear resistance of NiTi-YSZ coating samples. It is believed that the higher H/E value and pseudoelasticity effect of NiTi are two important factors which improved the wear performance of applied coatings. Also, to evaluate the role of addition of a NiTi (5 wt%)–YSZ buffer layer on the durability of YSZ coatings during wear operation, wear tests with a 20 N normal load and with a constant frequency were conducted on coated samples. It was observed that the conventional YSZ coating cracked and delaminated after about 60 m sliding distance. However, in samples which contain a NiTi (5 wt%) –YSZ buffer layer delamination was not observed until 100 m sliding distance which is attributed to the ability of NiTi for accommodation of interface stresses and hindering of premature delamination during wear test under higher loads.