Abstract
The nitriding process of solid state Ti-alloy by RF plasma was fundamentally investigated. Based on the results obtained in the nitriding process, reactive plasma spraying of Ti powder was carried out to fabricate the thick nitride coatings. The wear resistance of the nitride coatings was also evaluated by the conventional wear test.
The results obtained are summarized as follows:
(1) A linear relationship was recognized in the relation between thickness of the nitride layer and square root of nitride time. Therefore, the thermal plasma process seemed to be a diffusion dominating process.
(2) The diffusion rate of nitrogen in the Ti-alloy: Rd was estimated from the experimenal results obtained, and the plasma spraying of Ti powder was conducted under the deposition rate of less than Rd. By using this process, it was possible to fabricate the nitride coating with high deposition rate.
(3) It revealed that the nitriding degree of the coating could be changed by controlling the coating deposition rate. Based on this results, functionally gradient coating, whose compositional configuration changed from coating/substrate interface to coating surface, was fabricated by controlling the deposition rate.
(4) From the results of wear tests, it was found that the wear resistance property of the nitride coating obtained was equivalent to that of nitride layer on the Ti-alloy.
