The role of process parameters in plasma surface chromising of Ti2AlNb-based alloys

In order to enhance the wear resistance of Ti2AlNb-based alloy (O-phase), surface chromising was performed by double glow plasma process in this study. The effect of process parameters, such as temperature, time and pressure, on the microstructure, thickness, and micro-hardness of the alloyed layers was investigated. Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were employed to analyze the composition distribution and microstructure of the alloy. The results showed that the optimum process parameters were as follows: 970 °C for temperature, 4 h for chromising time, and 30 Pa for pressure. Following the optimization the thickness, microstructure and micro-hardness of the modified layer achieved the designed requirements. The results of tribological tests showed that the friction coefficient of the chromised layer was lower than that of the matrix at the room temperature or 500 °C, and the specific wear rate of samples with plasma chromising at either room temperature or high temperature was decreased markedly.