Abstract
MoSi2 of which melting point was high and which had excellence oxidation-resistance at high temperature was studied.
MoSi2 powder was deposited by low pressure plasma thermal spraying on the specimen with 50%Ni-50%Cr based coat after blasted on SS400 substrate. Then, residual stress generated in the specimen was determined. Compressive stress was produced in MoSi2 spray deposit. Tensile stress was produced in 50%Ni-50%Cr spray deposit except at the surface of SS400 substrate.
A series of the experiments were done so as to elucidate the validity of the obtained residual stress distribution.
Blasting on SS400 substrate, residual stress near the surface of the substrate was compressive and that of the inner part was tensile. After the blast treatment on SS400 substrate, depositing on the substrate with 50%Ni-50%Cr, residual stress in spray deposit was tensile. This was because SS400 substrate restricted the contraction of 50%Ni-50%Cr spray deposit which had large thermal shrinkage. Depositing MoSi2 after the blast treatment, compressive stress was generated in the. spray deposit. This was because the linear expansion coefficient of MoSi2 was extremely small comparing to that of the substrate nevertheless the temperature of the spray deposit was higher than that of SS400 substrate. As the result, the spray deposit restricted thermal shrinkage of SS400 substrate.
Obtaining residual stress produced by the thermal spraying, the importance of measuring the elastic modulus of sprayed deposit was indicated.
