The Effect of Oxygen Contamination on the Amorphous Structure of Thermally Sprayed Coatings of Cu₄₇Ti₃₃Zr₁₁Ni₈Si₁

this research has shown that it is possible to deposit coatings of gas atomized Cu{sub 47}Ti{sub 33}Zr{sub 11}Ni{sub 8}Si{sub 1} powders containing various levels of oxygen contamination using plasma arc spray methods. The structure of the coating was found to depend primarily on the spray environment, with an argon atmosphere producing the most amorphous samples for a given starting powder. The oxygen content of the coatings reflected the relative levels of the oxygen contamination in the starting powders. The analysis of the starting powders displayed oxygen contents ranging from 0.125-0.79 wt.%. It was shown that higher oxygen levels lead to more crystalline structure in the starting powders as determined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). This trend was found to be true for both the starting powders and for the plasma sprayed coatings. Chemical composition for all starting powders was very close to the nominal alloy composition. Chemical changes in the coatings involved the loss of Cu in coatings where high levels of oxidation were found. Cavitation erosion testing of selected coatings showed a weak trend that coatings prepared by vacuum plasma spray (VPS) had lower damage rates, but there was no clear data to indicate which coating parameters were superior. The range of data produced from testing duplicate coating was too wide to provide a good statistical measure of cavitation erosion resistance. of interest was the fact that when coatings began to show damage from cracking, all samples of a group showed similar damage and usually the damage pattern was somewhat unique to that group of samples. Failure of the coatings was due to features inherent to plasma arc spray (PAS) coating (i.e., pores, splat boundaries, oxide inclusions) rather than the mechanical characteristics of the amorphous alloy.