Microstructure characteristics and oxidation behavior of vacuum plasma sprayed tungsten disilicide coating

An efficient and effective method, vacuum plasma spray, has been utilized to fabricate tungsten disilicide coating in the present work. The phase composition and microstructure characteristics of the as-sprayed coating have been focused as well as its thermal stability and oxidation behavior from room temperature to 1500 degrees C. Results showed that the coating consisted of tetragonal WSi2 and a little amount of tetragonal W5Si3, presenting a uniform and lamellar structure with porosity less than 6%. The WSi2 coating was stable at temperatures below 500 degrees C, while rapid oxidization occurred between 800 and 1200 degrees C leaving loose and coarse surface consisting of mixed SiO2 and WO3. Excellent oxidation resistance at temperature range of 1300-1500 degrees C could be observed with dense and integrated SiO2 film formed on the coating surface. The oxidation mechanism was also discussed based on theoretical analysis, which could provide strong illustration of the oxidation processes of the WSi2 coating at different temperatures. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.