Influence of temperature on the phase structure, surface morphology, mechanical and tribological properties of Ti–N coatings prepared by MPCVD

Abstract

In this study, microwave plasma chemical vapor deposition (MPCVD) was introduced to prepare Ti–N coatings, and the phase structure, surface morphology, hardness and tribological properties were comprehensively investigated and discussed. The results showed that the phase in the coating was transformed from the mixture of TiN and α-Ti below 700 °C into TiN and Ti2N above 750 °C, and the content of TiN increases gradually with the increase of temperature. Moreover, the increasing temperature resulted in the growth of the Ti–N coating thickness, and the coating thickness prepared at 850 °C reached a maximum of 14.8 μm. The nitrogen content appeared gradient distribution, descending from the top surface to the matrix. The maximum hardness and modulus reached 30.58 GPa and 340.69 GPa after MPCVD treatment, respectively. The friction and wear test demonstrated that the MPCVD-treated Ti matrix presented lower wear volume and narrower wear track depth, indicating that the wear resistance of the coating sample was significantly improved. As a conclusion, the optimal MPCVD treatment temperature was 850 °C, which presented the thickest coating layer and the best overall mechanical properties. Compared with traditional plasma nitriding, MPCVD used microwave energy to excite the reaction gas to form plasma, which accelerated the heating and reaction, thereby improving the preparation efficiency of Ti–N coatings.