Effect of Heat Treatment on the Oxidation and High Temperature Wear Performance of Alloy Ti-6Al-4V Manufactured by Direct Metal Laser Sintering

Abstract

In this work, alloy Ti-6Al-4V was fabricated using direct metal laser sintering (DMLS) approach and studied the effect of heat treatment (solution treatment 950 °C/2h-furnace cooling and aging 550 °C/6h-air cooling) on the oxidation and wear performance at elevated temperature. The microstructural investigation revealed that as-built alloy consists of a fine-grained martensitic needle shape structure with columnar grains. In the solution treatment aging (STA) treated alloy, the rod-shaped β with different lengths of a was observed. As-built and STA-treated alloy Ti-6Al-4V were subjected to a cyclic oxidation test at 650 °C for 50 h in air. The reaction products developed on the sample’s surface are evaluated by scanning electron microscope (SEM) and X-ray diffraction (XRD). A thick TiO2 layer was formed on the alloy surface, and some cracks were noticed due to thermal stress. The high-temperature wear test was carried out on the Ti-6Al-4V alloy at room temperature (30 °C), 200, and 400 °C using a reciprocating pin-on-disc tribometer in dry conditions. The abrasive wear mechanism was found at RT, whereas oxidation and the adhesive mechanism were noticed at 200 and 400 °C. Results exhibited that STA alloy had a higher wear resistance than that of as-built alloy.