Tribological Behaviors Of Cr-Si Co-alloyed Layer Prepared On The Surface Of TA15 Alloy

As a category of near-? titanium alloy with middle strength, TA15 alloy has excellent comprehensive mechanical and technological properties, which is widely used in aerospace, military and civilian fields. However, due to low hardness and large friction coefficient, TA15 alloy has serious defects, such as adhesive wear, fretting wear and so on. These drawbacks greatly limit the application of TA15 alloy used as structural materials in security and reliability. In this paper, in order to improve the problem, Cr-Si co-alloyed layer was prepared on the surface of TA15 alloy by double glow plasma surface metallurgy technology, expecting that Cr-Si co-alloyed layer could effectively enhance the poor wear resistance.After successful preparation of chromized layer, the process of permeating Si was carried out, researching on the effect of temperature, voltage, work pressure and holding time. The best process parameters were determined by the composition, phase structure and surface hardness of Cr-Si co-alloyed layer. Then the friction and wear experiments were tested. This paper mainly investigated the tribological behaviors and analyzed the wear mechanisms of Cr-Si co-alloyed layer in the condition of different load, speed, temperature, friction pair and environment.The results show that:(1) The optimum process parameters for Cr layer are listed as follow: temperature: 950?, time: 3.5h, pressure: 35 Pa, distance between source electrode and work-piece: 15 mm, source voltage: 950 V, cathode voltage: 400 V. The optimum process parameters for Si layer are listed as follow: temperature: 950?, time: 3.5h, pressure: 35 Pa, distance between source electrode and work-piece: 15 mm, source voltage: 1000 V, cathode voltage: 450 V.(2) After the optimum process parameters of preparing Cr-Si co-alloyed layer, the thickness of the layer is about 40?m and the compositions present gradient distribution, composed of deposited and diffused layers.(3) XRD diffraction results show that Cr-Si co-alloyed layer is mainly composed of Si and Cr phases, as well as(Cr, Si) phases and(Ti, Si) phases.(4) The hardness and modulus of elasticity of Cr-Si co-alloyed layer are 10.371 GPa and 819.23 GPa respectively, which are four and five times larger than those of the matrix.(5) Ball-disk friction and wear experiments show that in the condition of different load, speed, temperature and friction pair, Cr-Si co-alloyed layer presents the slight worn morphology. The friction coefficient of Cr-Si co-alloyed layer fluctuates in the range of 0.2~0.3, which is lower than that of the matrix. At the same time, the wear volume and wear rate of Cr-Si co-alloyed layer are greatly reduced. The main tribological behaviors are abrasive wear, oxidation wear and delamination wear. The results reflect the excellent wear resistance of Cr-Si co-alloyed layer. However, in the condition of the seawater, Cr-Si co-alloyed layer shows the severe wear characteristics. The corrosion of the seawater aggravates the wear and the main tribological behaviors of Cr-Si co-alloyed layer are oxidation wear, corrosion wear and delamination wear.