The CoCrAlSiY alloy powder with Si mass concentrations of 0, 2% and 5% was prepared in this work. The oxidation kinetics curves of all three kinds of powders after 300 h oxidation at 1000 °C were plotted. In addition, the phase constitution of alloy powder and the distribution of β phase were analyzed by SEM and EDS. Furthermore, the effect of Si-addition on the melting temperature and oxidation resistance of the alloy powder were investigated by DSC-TG from the room temperature to 1400 °C. And the element concentrations at the grain boundary of alloy powder with Si addition of 2% were also analyzed. The results show that the melting temperature of alloy powder decreases as increasing Si content, which indicates that adding Si element could influence on the selective oxidation of Al and Cr elements in the alloy system, and improve the oxidation resistance of CoCrAlY powder. In addition, the weight gain of powder with Si addition of 2% is lowest. And Si element has a enrich tendency in the grain boundary. Therefore, the higher Si content would have a negative effect on the high temperature oxidation resistance of powder.

This study assesses the erosion resistance of WC-CoCr coatings produced from multimodal and conventional powders. The feedstocks were sprayed with a high-velocity oxyfuel (HVOF) torch using propane and kerosene as the fuels. Powder morphology and coating structures were analyzed by OM, SEM, and XRD. Coating properties including porosity, hardness, and fracture toughness were measured and erosion resistance was determined by dry sand blasting. The mechanical properties of WC-CoCr coatings deposited using kerosene are shown to be superior to those sprayed with propane. Multimodal WC-CoCr coatings deposited using kerosene had the highest microhardness and fracture toughness, the lowest porosity, and the greatest resistance to solid particle erosion wear.

Thermally grown oxide (TGO) that naturally forms on bond coat surfaces plays an important role in determining the lifetime of thermal barrier coatings (TBCs). Splashed particles on thermally sprayed MCrAlY bond coat surfaces are weakly bonded to the underlying bulk coating, leading to the formation of mixed oxides that contribute to TBC failure. In this study, various heat treatments are used to modify the weakly bonded splashed particles on LPPS CoNiCrAlY bond coats in order to restrain the formation of mixed oxides and prevent associated failures.

In this work a number of different WC-12Co powder formulations were applied to coupons of steel using HVOF (high velocity oxy-fuel) and DSC (detonation spray coating) spray techniques. Two different HVOF guns and a super detonation gun (Super D-Gun ) were used to apply the coatings. The coated specimens were heat treated in an inert atmosphere at various temperatures in the range of 540°C -1000°C and subsequently characterized using optical microscopy, a Vicker’s microhardness tester, SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction) to identify the phases generated. Additionally, in situ XRD was performed on a subset of these samples to explore the progression of the phase transformations as a function of temperature. Samples were also exposed to sand erosion with 20-30 mesh Ottawa sand at 825 feet per second to quantify performance. The work shows that the heat treatment and the transformation of amorphous metallic phases, WC and W 2 C to the η phase (Co 6 W 6 C) results in higher hardness and lower sand erosion rates.