Preliminary studies on the main characteristics and transient heat shock performances of detonation sprayed tungsten coatings on 316 L steel substrates

Abstract

Detonation spraying (DS) method was used to deposit tungsten coatings on 316 L steel substrates for the potential usage of the first wall of blanket in nuclear fusion devices. The main characteristics and anti-transient heat shock performances of the DS-W coatings were studied and compared with that of the atmospheric plasma sprayed tungsten (APS-W) coatings. The results showed that the DS-W coating had a very dense structure with its porosity of about 0.97%. The oxygen content of the DS-W coating that roughly detected with an energy dispersive spectrometer was much lower than that of the APS-W coating and the initial tungsten powders. It was considered that this result should be due to the unexpectedly introduced W2C during the DS process. These W2C would act as deoxidation agent and decrease the oxygen content in the coating. The microhardness of the DS-W coatings was much higher than that of the APS-W coatings and the pure tungsten bulk. It was analyzed that the dense structure, the reinforcement by W2C and the fine-grained strengthening effect during the DS process were responsible for this result. Furthermore, the DS-W/steel specimens exhibited excellent bonding strength and transient heat shock resistance. After having been tested under 3.5 MJ/m2 of transient heat loads, the DS-W/steel sample was still on a good status without obvious damages. Besides, it was believed that the overall performance of the DS-W coatings should be further improved through appropriate post-processing methods. As a conclusion, the DS-W coating demonstrated outstanding properties and its great potential for the application in plasma-facing materials.