Optimization of functionally graded W/SS 316L coating for fusion applications

W coatings have applications as a protective layer over the structural steel of the International Thermonuclear Experimental Reactor (ITER) temporary First Wall. In this work, a finite element simulation study of W/SS 316L functionally graded material (FGM) coatings was performed to determine the coating’s design parameters that reduce the thermal stress-discontinuity at the interface. Simulations considering only W coatings were performed initially to determine the ITER temporary First Wall equivalent thermal load conditions. Afterwards, the simulations of W/SS 316L FGM coatings were performed for varying the number of gradient interlayers while keeping the FGM thickness constant. Then, the FGM thickness was varied while keeping the number of gradient interlayers constant. In the simulations, the thermal load during the deposition and under the heat flux cycle of the ITER temporary First Wall were considered. Based on the simulation results, a 4-interlayer coating system with an FGM thickness of 0.8 mm between the top W coating and the steel substrate was recommended for the application.