Online monitoring of thermo cycles during laser remelting of flame sprayed chromia coating in pulsed mode and coating properties

A fiber laser operating in pulsed mode was used to remelt flame sprayed chromia coating. Time-temperature history of laser remelting process was captured using an infrared pyrometer. Temperature of the remelted zone remained steady during remelting. Average temperature increased with an increase in duty cycle and frequency. An improvement in surface roughness was found with an increase in the duty cycle and decrease in frequency. Porosity and inter-lamellar boundary of flame sprayed coating were obliterated upon laser remelting. A columnar grain growth perpendicular to the coating surface was observed. The as-sprayed coating harbored compressive residual stress that decreases with depth. Upon laser remelting, surface residual stress showed a tendency to become tensile. Wear coefficient of the remelted coating 70 % lower than those of the as-sprayed coating. The primary failure modes were splat delamination and radial cracking in as-sprayed and laser remelted coating, respectively. © 2020 Elsevier Gmb