Studying On Ti-TiN Two-layers Coating Prepared By Two-step Embedding Method

Ti-TiN two-layers coatings were obtained by a low cost two-step embedding method.The surface morphology，section morphology and chemical composition of Ti coating andTi-TiN two-layers coating were studied by the XRD，SEM and EDS. According to the resultsof this research，Analysis the growth mechanism and established the growth model of Ticoating and Ti-TiN two-layers coating.The studied of this paper provides basic data andtheoretical support for preparation of performance Ti-TiN two-layers coating useing a lowcost technology.The results show that，The thickness of the Ti coating increases obviously with theextension of embedding reaction time. That also became continuous and dense. choose thesample for embedding nitriding reaction whose Ti coating has a good quality on850℃、900℃and950℃respectively. The surface of rich Ti layer was obtained a continuous TiNcoating with a hardness between600Hk-800Hk by nitriding reaction on900℃. Therefor，Ti-TiN two-layers coating by two-step embedding method improve the hardness of thesubstrate alloy materials effectively.The paper analysis the growth mechanism and established the growth model of Ticoating according to the studied of phase consistent and morphology. The Ti coating whichobtained by embedding method was consistent of the lean Co layer，metastable Co-Tidiffusion layer，steady-state Co-Ti diffusion layer and rich Ti layer. The growth process of theTi coating can be described as transfer reaction，mutual diffusion reaction and penetrationdiffusion. And mainly by the control of Co、Ti atomic mutual diffusion. The Co2Ti phase isthe Priority generate phase which in Ti coating formation on800-850℃，However，thePriority generate phase is CoTi2phase on900-950℃.At the same time，The paper analysis the growth mechanism and established the growthmodel of Ti-TiN two-layers coating according to the studied of phase consistent andmorphology. A large number of Co atom diffusion from Ti coating internal to the surface，andformation by the reaction with Ti atomic in rich Ti layer during the nitriding reaction process.The exist of this Co-Ti system inter-metallic compound strong inhibition N atom diffusion torich Ti layer，Further limits the growth of the Ti coating. Between the TiN and rich Ti layer has excellent adhesion properties because of the content of N atoms in the rich Ti layer ischanged of gradient.