Atmospheric plasma spraying of functionally graded steel/tungsten layers for the first wall of future fusion reactors

Abstract Functionally graded steel/tungsten layers may be used as interlayers in the first wall of future fusion reactors to balance thermally-induced stress peaks in the steel‑tungsten joint. In this work, a modified water-stabilized atmospheric plasma spraying set-up is used to deposit uniform and functionally graded steel/tungsten coatings at elevated substrate temperatures. Uniform coatings were used to characterise individual sublayers of graded coatings in detail. The thermal expansion, thermal conductivity, Young's modulus and yield strength of the layers are promising for the application in steel‑tungsten joints and can be explained by microstructural observations. Only at a substrate preheating temperature of 900 °C the formation of intermetallic precipitates during deposition was observed.