Preliminary studies on detonation sprayed W/W-steel composite coating materials on steel substrates for the first wall of blanket

Abstract

The mismatch of the thermo-mechanical properties of tungsten and steel would lead to large thermal stress between detonation sprayed (DS) tungsten coatings and steel substrates. DS W-steel composite coatings were prepared on 316 L stainless steel (SS) substrates as the interlayer of DS-W coatings to solve this issue. The DS-W coatings manufactured on 316 L SS substrates without interlayers were used for comparing. The surface and cross-section morphologies showed the composite coating material was dense steel lamellas-stacked structure in which tungsten particles dispersed homogeneously. The EDS and XRD results showed the composite coating was consisted of three different textures: W, SS and W-SS compound alloy. But the tungsten content in the coating was lower than the expected 50 vol% due to the low deposition efficiency of the tungsten powders. The Vickers hardness of the composite coating was 577– 647 HV which was between that of the DS-W and the SS substrate. The bonding strengths of the DS W/W-SS/SS substrate three-layer coating samples and the DS-W/SS substrate coating samples were about 61.33 MPa and 52.45 MPa, respectively. Besides, the three-layer samples had better performance under the transient heat shock tests than that of the DS-W/SS substrate samples. All these results proved the addition of the DS W-SS composite interlayers improved the overall properties of the DS-W/SS substrate system. The relatively low tungsten content in the composite coatings should be optimized to further improve the performance of the three-layer coating system in the following.