“…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].…”