Oxidation sequence modulation induced superior high-temperature tribological performance of Ti-Hf-Nb-V refractory high entropy alloy fabricated through directed energy deposition

Abstract

To fulfill the demands of applications under severe operational conditions, alloys should possess outstanding wear resistance at elevated temperatures. A Ti-Hf-Nb-V based refractory high entropy alloy (RHEA) was successfully produced using the directed energy deposition (DED) technique, which avoided the formation of fatal defects and showcased well-performed mechanical properties across a broad temperature spectrum. Strategic design of the oxidation sequence enabled the early formation of oxide nanolayers, which can form a polycrystalline oxide nanocoating under a complex stress condition to drastically reduce the wear rate from 2.69 × 10–4 mm3·(N·m)−1 at room temperature to 6.90 × 10–7 mm3·(N·m)−1 at 600 °C. These results indicate that the application of additive manufacturing to fabricate RHEAs with superior wear resistance at high temperatures paves the way for the development of functional coatings designed to withstand extreme conditions. 为了满足严苛条件下的应用需求，合金通常需要具备优异的高温耐磨性能。通过定向能量沉积技术制备的Ti-Hf-Nb-V难熔高熵合金，没有形成致命的缺陷，并在较宽的温度范围内表现出良好的机械性能。通过设计该合金中的氧化顺序，在摩擦磨损实验中可以形成氧化物的纳米层。在600℃下，该氧化物纳米层的形成能够显著降低磨损率，由室温下的2.69 × 10-4 mm3·(N·m)-1显著降低至6.90 × 10-7 mm3·(N·m)-1。该结果表明，通过增材制造可以制备具有优异高温耐磨性能的难熔高熵合金，并为开发能够承受极端条件的功能涂层开辟了新途径。