On-line temperature monitoring of plasma sprayed coating is presented, which is based on IR pyrometery combined to robot trajectories. Temperature fields of the substrate before spraying and the deposited coating when the damage happens are taken to investigate the temperature fluctuation information. Experimental results demonstrate that coating damage always occurs in the temperature transition area of the substrate from the higher to the lower, as well as the higher temperature area. The temperature difference between the peak and the mean of the relevant regions is beyond 30 - 50℃ or even higher. This case provides the omen of coating damage and the focusing scopes for the process control of coating temperature in plasma spraying
