Nb-C alloyed layer prepared on TiAl alloys by plasma treatments and its first-principles investigation

摘要

A Nb-C alloyed layer formed on TiAl by plasma Nb alloying followed by carburization was investigated. The alloyed layer was characterized using SEM, TEM, XRD and GDS. Effects of Nb alloying and the carburizing atmosphere on microstructure of Nb-C alloyed layers were analyzed. The forming mechanism of the Nb-C alloyed layer was verified using first-principle calculation. The results reveal that the Nb-C alloyed layer is composed of NbC and Nb2C. An addition of niobium in TiAl accelerates the diffusion of carbon atoms in the Nb-alloyed layer, leading to a thicker alloyed layer with higher carbon content. The carbon concentration and diffusing depth increase with methane gas. First-principle calculation shows that the forming energy of Nb-C duplex-treated TiAl is lower than those of single carburized TiAl and Nb-alloyed TiAl.