Sealing Oxides of Thermal sprayed Alumina Coating and Its Formation Process

Abstract

The sealing of pores by a veined oxide in a thermal sprayed alumina coating with some kinds of metal particle was investigated by heating in air. Also, the oxide grew from the metallic substrate into an artificial pore in the alumina block was observed after heating in air. The sealing of pores arose by the spinel oxide in the alumina coating containing Ni, Co or NiCrAlY particles after heating at 1173K for 100h in air. The oxide grew from Ni substrate into the artificial pore in alumina block after heating at 1273K for 100h in air. The oxide formed from the Ni substrate in the pore consisted of NiO (core) and NiAl₂O₄ spinel oxides. Also, the NiAl₂O₄ spinel formed from the top of the grown oxide on the surface of the pore. The spinel oxide preferentially forms on the surface of the pore and the primary oxide of the metal occupies the remaining space in the pore.