The Ni-based single crystal superalloy has an excellent performance derive for high temperature fatigue strength. So, the expansion of application has been expected mainly in advanced gas turbine parts. However, it is known that the γ′ microstructure changes inside the material by plastic strain processing and heat-treatment. As a result, the fatigue strength was remarkably reduced. The new phenomenon was found that the B containing alloy coatings formed by thermal spraying restore high temperature fatigue strength of the weakened single crystal superalloy. We introduce the improvement effect of high temperature fatigue strength achieved by means of spraying the B containing alloy to CMSX-4 Ni base alloy substrate produced alterated layer.