Study on nanomechanical and high temperature tribological behaviour of Ti2AlNb based alloys by plasma surface alloying

Plasma chromising and carburisation following plasma chromising (duplex treatment) were carried out on the Ti2AlNb based (O phase) alloys by the double glow plasma process. The dynamic ultramicro hardness and elastic modulus of the alloyed layers were investigated by the nano-indentation technique. Dry sliding friction tests on the samples against silicon nitride (Si3N4) balls were completed at high temperature by a ball-on-disc tribometer. The results indicated that the duplex-treated layer was mainly composed of Cr23C6 and Cr2Nb, while the chromised layer was consisted of Al8Cr5 and Cr2Nb phases. The ultramicro hardness of the duplex-treated layer was higher than that of the chromised layer, whereas the elastic modulus of the duplex-treated layer was lower than that of the chromised layer. The wear rates of the duplex-treated layer and the chromised layer were similar to 6.6 and 2.5 times respectively, lower than that of substrate. The duplex-treated layer exhibited excellent high temperature wear resistance.