A gas dynamic method,to estimate the mixed-mean gas temperature in a stagnation chamber of a cold spray nozzle,is proposed.The method does not use thermocouple but mass flow rate of the process/carrier gases and stagnation pressure upstream of the nozzle.The mixed-mean gas temperatures estimated by the present method were validated by comparing them with measured values using a coiled sheath-type φ0.5mm thermocouple,inserted in the stagnation chamber of the nozzle.The gas flow experiment of cold spray was conducted under the conditions of gas pressure up to 0.96MPa,and heaterexit gas temperature up to 673K.The working gases selected were air and helium.The species of the process gas and the carrier gas was the same.The ratios of the mass flow rate of the carrier gas against that of the total mass flow rate selected were 0,0.20 and 0.33 for air,0 and 0.20 for helium as working gas.The comparison of the estimated and measured mixed-mean gas temperatures shows that the estimation error of the present method is less than 3% for air,and less than 5% for helium gas.

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Thermal sprayed MCrAlY coatings are applied to protect the substrate against high temperature oxidation and corrosion in the field of gas turbine components.In generally,CoNiCrAlY is used as a bond coat in thermal barrier systems(TBCs).CoNiCrAlY coatings are coated by various thermal spraying processes,LPS,HVOF,and APS.However,APS process is not used as a bond coat in TBCs,because of their poor performance in oxidation or corrosion resistance.We have been researched about characteristics of high temperature oxidation of MCrAlY coatings coated by APS.In this study,the high temperature oxidation resistance of CoNiCrAlY coatings with several conditions were evaluated,in particular,using CoNiCrAlY powders of different sizes were investigated.It has been obtained that oxidation resistance of thermal sprayed CoNiCrAlY coating are good relationship with powder size.

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