High-temperature tribological behaviors of Ti2AlNb-based alloys by plasma surface duplex treatment

Plasma tungstening followed by carburization(W-C duplex treatment)was performed on the Ti2AlNb-based(O phase) alloy by using the double glow plasma process to enhance its wear resistance.The microstructure and high-temperature tribological behaviors of the un-treated and W-C duplex-treated samples were investigated.The results show that the duplex-treated layer is mainly composed of W2C or W6C2.54 phases and the contents of W and C elements in the alloyed layer change gradually along the depth by surface plasma duplex treatment.The diffusion depth of W is about 12μm,while the carbon atoms most exist in the depth more than 12μm.High temperature tribometer tests indicate that the friction coefficient of the W-C duplex-treated layer is approximately 1/6 that of substrate.The wear rate of the duplex-treated layer is about 28%that of the untreated one.So,plasma surface W-C duplex treatment can obviously improve the high-temperature tribological resistance of Ti2AlNb-based alloy.The tribological mechanism of the duplex-treated layer is discussed by dividing the friction process of the duplex-treated layer into three fluctuate stages.The first stage is the formation of oxide film between W-C duplex-treated layer and counterface.The second stage is the detachment of oxide film,acting as "the third body" .The last stage is the period that the friction and wear occur between the compact particle layer and counterface.