Enhanced high-temperature wear behavior of high-speed laser metal deposited Al0.3CrFeCoNi coatings alloyed with Nb and Mo

Abstract

In this study, oscillating wear tests were carried out on the high-speed laser metal deposited (HS-LMD) high-entropy alloys (HEAs) Al0.3CrFeCoNi, Al0.3CrFeCoNiNb0.5 and Al0.3CrFeCoNiMo0.75 at temperatures of 25 °C, 500 °C, 700 °C, and 900 °C. The microstructure was analyzed using scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS). In addition, the crystal structure was investigated by X-ray diffraction (XRD). Furthermore, the Vickers hardness (HV0.1) was determined on cross-sections. All tests were performed before and after the high-temperature wear tests. The wear depth was measured using laser scanning microscopy. Increasing the temperature leads to decreased wear depth, particularly for the Nb- and Mo-containing HS-LMD coatings. The wear mechanisms change from abrasive, adhesive and oxidative wear to pronounced oxidative wear. The adhesion of the oxide layer is most important for high wear resistance at elevated temperatures. Strong adhesion is attributed to compact, thin and mechanical clamped oxide layers, which are found for the Nb-containing HS-LMD deposited coating resulting in the lowest wear depth.