| Titanium and its alloy is widely used as an integral part of material in the aerospace industry due to their high specific strength, low modulus of elasticity, well heat resistance and high corrosion resistance. However, the use of titanium and its alloys in industry have been limited due to their poor wear resistance properties and low hardness. So, a well surface modification to titanium has become the most important issue to solve these problems.Solid boronizing technology is a traditional method in surface modification filed. It has several advantages such as simple and convenient, easy controlling, high hardness in boride layer. Therefore, in this paper, the solid boronizing technology has been used to obtain the boride layer on the surface of Ti6A14V. The main ingredient of boronizing agent for boron source is FeB.Temperature and time are the main factors to affect the performance of boride layer. Thus, we select the boronizing temperature respectively at940℃and860℃, the preservation time in two and four hours. The thickness, microstructure, phase structure and hardness of boride layer in different processes have been analyzed. The tribological properties of Ti6A14V substrate and the boride layers have been studied by ball-on-disc test. The CS350electrochemical test system has been used for testing the corrosion resistance of boride layer in0.6mol/L NaCl solution.From the experimental results, the following conclusions were obtained:1. After boronizing treatment, a certain thickness of the boride layer has been formed on the surface of Ti6A14V substrate. X-ray diffraction analysis shows that the boride layer is composed by TiB and TiB2two-phase compounds. EDS analysis shows that the existence of the B element forced the Al element on Ti6A14V surface to migration to the internal.2. When the boronizing temperature is940℃, the surface of the boride layer has a number of round particles. However, at the boronizing temperature of860℃, its surface formation becomes to be needle tissue distribution and tightly packed. The organization of the surface particles after2h boronizing are smaller than4h’s. This phenomenon may be due to the increase of holding time. The hardness of the boride layer changes gradually from surface to substrate.3. Under the boronizing temperature of940℃and holding time2h and4h, the friction coefficients of boronization layer are0.24and0.22respectively. These" are smaller than that of the Ti6A14V substrate, whose friction coefficient is0.38. The above results show that the boron layers have a well anti-friction effect at940℃. As the same theory, when the boronizing temperature is860℃ and holding time is2h and4h, the friction coefficient of boronization layer are0.42and0.40respectively. They are larger than that of substrate, so the anti-friction effect of the boride layers is not obvious.4. From the analysis of wear scar morphology and contour after wear test, we can find that the wear scar of substrate is wider and deeper. Which indicate that the wear resistant of boride layer is better than that of substrate. The calculation and analysis of wear volume show that the wear volume of substrate is568times of sample1#(940℃×2h),6times of sample2#(940℃×4h),2times of sample3#(860℃×2h),8times of sample4#(860℃×4h).5. The polarization curve in0.6mol/L NaCl solution indicates that:the corrosion current density of substrate is the smaller than that of boride layer, so the substrate has the slowest corrosion rate; the self-corrosion potential of sample2#(940℃×4h),3#(860℃×2h)and4#(860℃×4h)is higher than that of the substrate, so the sample2#(940℃×4h),3#(860℃×2h)and4#(860℃×4h)is not easy to be corroded in self-corrosion potential. |
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