High Temperature Performance And Synthesis Process Of In-situ Reaction Composite Coating On TC11 Titanium Alloy

Titanium alloy has become concerns of people,because of the advantage of high specific strength,high corrosion resistance,excellent high-temperature performance and well biocompatibility.In terms of aviation industry,titanium alloy has become backbone material for improving engine high thrust-weight ratio and working temperature.With requirement of higher thrust-weight ratio,the working temperature has been increased dramatically.The high temperature oxidation resistance has been insufficient in this severe high temperature environment.There are two kinds of defend measures.The first one is to dope element to develop new system titanium alloy,but it is high cost and much time for this measure.Compared with above mentioned,adding coating is more economical and insufficient,which is applied wildly to enhance oxidation resistance.The common coating includes Al-diffusion coating,MCrAlY covered coating and Al₂O₃ ceramic coating,but it presents deficiency of stability and bonding performance.Thus,to solve the above problems,this paper takes advantage of micro-arc oxidation?MAO?technique,magnetron sputtering technique and in-situ reaction synthesis technique to prepare high temperature oxidation resistance gradient composite coating.The research scheme has been confirmed as followed,due to the research and experiment at home and abroad.Firstly,The electrolyte,voltage and time of MAO has been investigated by orthogonal test,as well as the sputtering rate of magnetron sputtering and the temperature of in-situ reaction synthesis.The optimized process of ideal in-situ reaction composite coating has been selected.Secondly,the bonding performance test indicated that the bonding force is 48.5MPa of in-situ synthesis composite coating sample,35.0 MPa of contrast sample1?magnetron sputtering+thermal diffusion?and 48.5 MPa of contrast sample 2?MAO+SG?at room temperature.The thermal shock curve of in-situ synthesis composite coating obeys parabola rule and never spalls compared with another two contrast samples.Finally,The isothermal oxidation test has carried out among bare alloy,MAO coating and composite coating at 600?,700?and 800?.The results show that the?-Al₂O₃ layer as barrier layer at lower temperature has excellent oxidation resistance.The oxidation rates of composite coating are0.01,0.01 and 0.03 mg²/cm⁴·h at 600?,700?and 800?,which is 1/2,1/4,1/85 of MAO coating sample and 1/2,1/10,1/265 of bare alloy sample.In brief,the in-situ composite coating has excellent bonding performance and oxidation resistance.It raises the working temperature from 550?to 700?,which conforms to the demand of high thrust weight ratio engine.