Oxidation Behavior Of Ta-W-Ti-Al Refractory Complex Concentrated Alloys

Traditional metals and alloys have reached the limit in their high-temperature application.Refractory alloys are one of the materials to solve this problem.However,the high temperature oxidation resistance of refractory alloy is relatively poor that seriously restricts the application of refractory alloy.Many methods have been researched to improve the oxidation resistance of refractory alloy,in which the antioxidant surface coating method is a main way to improve the oxidation resistance of alloy.A relatively new design concept,refractory complex concentrated alloys?RCCAs?represent for improving high temperature oxidation resistance of alloys.While,no unified description and/or predictive modeling capabilities have been widely accepted and implemented to describe RCCA oxidation.The paper presents a thorough investigation of the oxidation behavior of TaWTiAl RCCAs.The evolution of oxide scales after the alloy was oxidized in air was discussed with the prolonged oxidation time and the increase of oxidation temperature.The oxidation kinetics of less complex ternary TaWAl alloy?TWA?and TaWTiAl?TWTA?alloys also have been studied,the results are as follows:?1?After oxidation at 900?,dense and continuous oxide outer layer consisted of Al₂O₃ and the inner oxide layer consisted of?Ta₂O₅+WO₃+Al₂O₃?solid solution was formed at initial stage for the hot pressing sintering TWA alloy.The oxidation kinetics of alloys in short time followed pseudo-parabolic law.However,with prolonging oxidation time,the oxide film was pulverized and peeled off,and the kinetic of alloy was governed by linear law kinetics.?2?The continuously mixed out oxides layer was formed in the two hot-pressure?HP?sintered TWTA alloys for after oxidation at 900?.The oxidation kinetics of TWTA alloys followed parabolic law.At the same time,the oxidation resistance both alloys achieved complete level according to the oxidation eesistance evaluation standards.?3?With the increase of the oxidation temperature,the oxidation resistance time continuously shortened and the oxidation resistance weakened for HP sintered TWA alloy.And the oxidation kinetics curves also changed from parabolic to line law for the two HP sintered TWTA alloys.The increase of Ti content reduced internal stress and improved the oxidation resistance of alloys.?4?The oxidation behavior of TWTA-2-X prepared by vacuum suspension melting showed that in the initial stage,the oxidation layer of the mainly composed of the TiO₂ and?Ta₂O₅+WO₃+TiO₂+Al₂O₃?solid solution at 1000?.With the increasing of oxidation duration,the oxides scale shown an outer layer mainly composed of TiO₂,Al₂O₃ and solid solution,which hindered the oxidation of the alloy.The alloy effectively avoided the phenomenon of element enrichment,high oxygen content and preferential oxidation in alloy structure by vacuum suspension melting,and improved the oxidation resistance of the alloy.