Comparison of high-temperature friction and wear behaviours of Ti6Al4V produced by additive manufacturing and casting

Additive manufacturing (AM) methods, especially selective laser melting (SLM), have recently attracted attention because they enable the quick and easy production of complex parts that cannot be produced with traditional manufacturing methods. However, residual stresses in the fabricated components impact their mechanical characteristics and may necessitate additional heat treatments. In this study, SLM-produced Ti6Al4V parts were subjected to a stress relief treatment under argon gas at 790°C for 2 h. The microstructure, microhardness and high-temperature tribological properties were examined comparatively with the traditional casting method. Dry sliding tribological experiments were carried out at different temperatures up to 600°C to compare high-temperature performance. It has been determined that the microstructure of samples produced by casting and SLM comprised β and α phases. The casting sample had 66.02% α grains, whereas the SLM sample had 59.02% α grains. The average microhardness in the SLM sample was marginally higher than that in the casting due to the formation of martensitic α. The results showed that wear rates increased with temperature for each sample. SLM samples exhibited slightly higher wear rates at each test temperature compared to the casting sample, which is attributed to the oxidative wear mechanism. The higher percentage of oxygen in the triboxide layers in the casting sample increased the wear resistance. When examining friction coefficients, an increase in average friction coefficients was observed at a test temperature of 300°C, while a decrease was observed at a test temperature of 600°C.