Research For High Temperature Protective Effect Of TiAlCr Coating On High Temperature Titanium Alloy

TiAlCr protective coatings on high temperature alloys were prepared first on the nearαhigh temperature titanium alloy surface by multi-arc cathode technology with the TiAlCr alloy targets. The proper deposition parameters were selected after the discussion of the surface morphology, texture structure, deposited speed rate and adhesion strength. Then two TiAlCr alloy coatings with various contents were prepared at this parameter. The isothermal oxidation behavior of the coatings was tested at 600℃, and the cycle oxidation behavior was investigated at 700℃. The oxidation kinetics curve was drawed. The surface morphology of the coatings oxidized for different time at 600℃and 700℃were observed and analyzed by Metallurgical Microscopy and SEM. The oxidized process at the high temperature is discussed, and the resistance of high temperature oxidation is appraised. The room-temperature tensile performances of the samples with and without coatings before and after 600℃/100h and 650℃/100h bright thermal exposure were tested. The effect of TiAlCr alloy coatings on the tensile performance were discussed and appraised.There is no change of the microstrure of the two coatings after isothermal oxidation at 600℃for 100h, and no obvious lengthways diffusion inferred by the changes before and after oxidation. XRD shows that the oxide only includesθ-Al2O3 and TiO2. The results of the cycle oxidation test at 700℃show that the oxidation kinetics curves of the two coatings all obeys the parabolic law, the oxidation resistance of 2# coating with higher Al content is more intensive than 1# coating, and the two coatings can improve the oxidation resistance of the alloy substrate. Though the continuous and compact protected Al2O3 on the surface of the two coatings is not formed during the whole oxidation process, oxidied speeds of the two coatings all slow down when the primary oxidation stage is over. The oxidied speed of 1# coating is basically invariability during the following oxidation process because of the lower Al content and the Cr doped effect. During the oxidation medium term of the 2# coating, the steady oxidation state is appeared due to the abundantθ-Al2O3 on the coating surface. As results of the Ti competive growth and the Cr doped effect, the time of the steady oxidation state is shorter, and falls into the unsteady oxidation state. The falling of the room-temperature tensile performance of the high temperature titanium alloy with TiAlCr coatings is buffered by comparing before and after the room-temperature tensile performance.It is indicated by this study that: the deposition of TiAlCr high-temperature-protective coating by multi-arc cathodic technology is feasible., and it is full of actural value and developmental promising. Deposited bias, target composition, coating composition, microelement addition, tensile plasticity are needed to be studied further to optimize the protection of TiAlCr alloy coatings.