INFLUENCE OF LASER-SURFACE REMELT ON HIGH-TEMPERATURE OXIDATION OF A LOW-PRESSURE PLASMA-SPRAYED AMDRY997 OVERLAY COATING

An AMDRY997 overlay coating on IN100 superalloy substrate was laser re melted using a solid state YAG laser with power of 20-30 watts. Oxidat ion tests at 900-1100-degrees-C demonstrated that the oxidation resist ance of the diffused coatings was significantly enhanced by laser surf ace remelt. The oxide scales formed on both the diffused and the remel ted coatings all exhibit excellent spallation resistance. The oxide sc ale on the remelted coatings was thinner with better protectiveness an d 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 crystallite s, and a rather uniform distribution of active elements. Surface segre gation of yttrium on the coating surface, enabled the nucleation and f ormation of a compact alumina scale.