Effect of Vacuum Carburizing Time on Microstructure and Mechanical Properties of Tantalum Carbide Layer

A (TaC/Ta2C) carbide bilayer is obtained by vacuum carburizing technology on the surface of Ta substrate at 1673 K for 4, 8, and 12 h. XRD, SEM and EBSD are utilized to investigated phase composition and the microstructure. The mechanical properties of the Ta and tantalum carburized materials are studied with Vicker's hardness tester and nanoindenter, adhesion automatic scratch tester, reciprocating friction and wear testing machine. The results show that the outside surface phase composition of the carbide bilayer is all the TaC phase. With the increase of the carburizing time from 4 to 12 h, the average grain size from approximately 500 nm to 10 mu m, the thickness of the carbide bilayer is from 11 to 20 mu m. The microhardness increases from 104.1 to 322.5 HV, and the elastic modulus are from 466.6 to 615.3 GPa. Adhesive strength is best at 8 h, 49.1 N, compared to 19 N at 4 h and 36.5 N at 12 h. The friction and wear coefficient of Ta fluctuates significantly between 0.6 and 1.0, after carburizing treatment, the friction and wear coefficient fluctuates smoothly, and the wear resistance is well improved.