大気中溶射でNi-Cr合金中に形成される酸化物と加熱によるその変化

概要

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A nickel-chromium alloy powder containing 19.0mass% chromium was plasma sprayed and flame sprayed in air onto a mirror polished nickel substrate to collect individual splat and a grit blasted steel substrate to obtain deposits. Chromium oxide was hardly detected by electron probe microanalysis at the splashed splat/cold nickel substrate interface and was often present at the disc shaped splat/hot nickel substrate interface. The deposits were composed of alternate lamellae of alloy and chromium oxide. The alloy/oxide interface in the as sprayed deposits was smooth. On heat treating the deposits at 1073K, the interface becomes wavy, and at higher temperatures the oxide layer granulated. A mechanism is proposed for this granulation, which takes into account the balance of the interfacial tensions at the triple point at which a grain boundary in the oxide layer or the metal layer meets the alloy/oxide interface.