Effects of nitrogen flux on microstructure and tribological properties of in-situ TiN coatings deposited on TC11 titanium alloy by electrospark deposition

Abstract

In order to improve the tribological properties of titanium alloys, the in-situ TiN coatings were prepared by electrospark deposition (ESD) on the surface of TC11 titanium alloy. The effects of nitrogen flux on the microstructure and tribological properties of TiN coatings were investigated. The results show that the coating is relative thin when the nitrogen flux is small and mainly consists of Ti2N, α-Ti, TiO and TiN phases, and the metastable phase of Ti2N is developed due to the rapid solidification of ESD. While in excessive nitrogen flux condition, many micro-cracks and holes might be generated in the coating. In moderate nitrogen flux, the coating is mainly composed of TiN phase, and is dense and uniform (50–55 μm). The average hardness is HV0.2 1165.2, which is 3.4 times that of the TC11 substrate. The TiN coatings prepared in moderate nitrogen flux perform the best wear resistance. The wear loss of the coating is 0.4 mg, which is 2/9 that of the TC11 substrate. The main wear mechanisms of the coatings are micro-cutting wear accompanied by multi-plastic deformation wear.