Influence of laser surface remelt on high temperature oxidation of a low pressure plasma sprayed AMDRY997 overlay coating

Abstract
An AMDRY997 overlay coating on IN100 superalloy substrate was laser remelted using a solid state YAG laser with power of 20-30 watts. Oxidation tests at 900-1100 °C demonstrated that the oxidation resistance of the diffused coatings was significantly enhanced by laser surface remelt. The oxide scales formed on both the diffused and the remelted coatings all exhibit excellent spallation resistance. The oxide scale on the remelted coatings was thinner with better protectiveness and seemed to be high in alumina. The diffused samples had thicker oxide scales and considerable internal oxidation along the inherent pores. Laser modified coatings had microstructures with very fine crystallites, and a rather uniform distribution of active elements. Surface segregation of yttrium on the coating surface, enabled the nucleation and formation of a compact alumina scale.