Effects of yttrium on microstructure, mechanical properties and high-temperature wear behavior of cast Stellite 6 alloy

Effects of alloying yttrium on the wear behavior of a commercial wear-resistant alloy, Stellite 6, at elevated temperatures were investigated. Samples of Stellite 6 alloyed with various amounts of yttrium were made using an arc-melting furnace. Structure of the modified Stellite 6 was analyzed using the X-ray diffraction technique (XRD). The wear behavior of the samples at various temperatures from the room temperature up to 650 °C was evaluated using a high temperature pin-on-disc tribometer. It was demonstrated that the alloyed yttrium considerably improved the alloy with improved wear resistance and mechanical behavior. In order to better understand the effect of yttrium on high-temperature wear behavior of the alloy, the structure and mechanical properties of oxide scales developed on Y-containing and Y-free samples were investigated, respectively, employing the grazing incidence XRD and nano-indentation techniques. The resistance of the oxide scales to scratch failure was also investigated using a micro-scratcher with in situ monitoring changes in the contact electrical resistance. It was demonstrated that the oxide scale was considerably enhanced when yttrium was added to the alloy, which could contribute to the improved performance of the alloy at elevated temperatures.