Abstract

An investigation has been undertaken on the analysis of residual stress in glass coatings during plasma spraying. Theoretical analysis and in-situ experimental measurements show that the residual stresses in glass coatings are particularly sensitive to the heat input from the plasma flame, since this can raise the temperature to above the glass transition temperature. Control of the spraying parameters enables the quench stress of splats to be relaxed by the end of the spraying and the only significant remaining source of stress derives from the differential contraction between the coating and substrate during cooling. The analysis also shows that a stress transition occurs during cooling and that the sign of the final residual stress depends upon the expansion coefficient of the glass. The residual stresses are shown to govern the critical coating thickness for cracking and the coating adhesion.

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