Development of high-grade VPS-tungsten coatings on F82H reduced activation steel

Tokunaga, Tomonori*; Watanabe, Hideo*; Yoshida, Naoaki*; Nagasaka, Takuya*; Kasada, Ryuta*; Lee, Y.-J.*; Kimura, Akihiko*; Tokitani, Masayuki*; Mitsuhara, Masatoshi*; Hinoki, Tatsuya*; Nakashima, Hideharu*; Masuzaki, Suguru*; Takabatake, Takeshi*; Kuroki, Nobuyoshi*; Ezato, Koichiro; Suzuki, Satoshi; Akiba, Masato

VPS-W coating formed on F82H kept at about 873K in conventional plasma spray conditions has inhomogeneous texture; namely mixture of disarranged area composed of large re-solidified/un-melted grains, fine randomly oriented grains and pores, and well ordered area composed columnar grains. Heat load test indicate that elimination of the disarranged area is necessary to improve the heat load resistance of VPS-W. One can get W coating with texture of homogeneous columnar crystal grains by eliminating the re-solidified/un-melted large particles. Optimization of the W powder size was also effective to reduce number of randomly oriented fine grains and pores.