Modification of vacuum plasma sprayed tungsten coating on reduced activation ferritic/martensitic steels by friction stir processing

Impacts of friction stir processing on irradiation effects in vacuum-plasma-spray coated tungsten

“…Both the H IT are larger than that of bulk-W (∼7 GPa). In the accompanied paper [6], the Vickers hardness (H V ) value of the as-VPS-W is smaller than that of the VPS-FSP × 2-W with a large scatter. This discrepancy is possibly explained by the difference of indentation size and the influence of inherent defects; the H V value of the as-VPS-W is inevitably affected by porosities at inter-particles in its relatively larger plastic deformation area, while the FSP-ed VPS-W have less porosities, resulting in higher H V value with a smaller scatter.…”

“…All tests were conducted with a contact depth of 300 nm. For the VPS-FSP × 2-W samples, indentations were carried out around the positions around 0.5 mm apart from the FSP-ed surface, because its Vickers hardness depends on the distance from the surface [6]. The test results were analyzed in accordance with the method by Oliver and Pharr [9].…”

“…Our group reported that FSP was firstly applied to VPS-W and that its hardness and thermal conductivity was successively improved in unirradiated condition [6]. Fine-grain and * Corresponding author.. E-mail address: ozawa.kazumi@jaea.go.jp (K. Ozawa).…”

“…Among the W layer, (2) is the region only VPS was performed, and (3) the one both VPS and FSP performed. Detail procedure and basic physical, mechanical and thermal properties of both materials are given in the accompanied paper [6]. The surfaces to be irradiated was polished metallo-graphically up to 0.05 m alumina powder with a buff cloth.…”

Thick tungsten coating on ferritic–martensitic steel applied with a vacuum plasma spray coating method

“…Also, the large mismatch of thermal expansion coefficients between a tungsten block and a heat sink such as copper can cause cracking and delamination [4,7]. Recently, direct tungsten coating on the heat sink or on the structural materials has been performed to overcome these disadvantages [5,[8][9][10][11][12][13][14]. Among the possible coating technologies such as thermal plasma spray, physical vapor deposition, and chemical vapor deposition, a thermal plasma spray coating method is preferred due to its high coating rate and uniform coating for thicker layers [5,[8][9][10][11][12][13][14][15][16].…”