Systematic investigation of residual strains associated with WC-Co coatings thermal sprayed onto metal substrates

Using penetrating high-energy synchrotron X-ray radiation and thermal neutrons, the residual strains and stresses associated with the high-velocity oxygen-fuel (HVOF) thermal spray coating of WC-Co on two different substrate materials with significantly different coefficients of thermal expansion (CTE) to that of the coating material, have been investigated in a systematic approach. This approach enabled quantification of the residual strain and stress contributions that emanate from the different processing steps associated with the coating process. An eigenstrain approach enabled direct comparison of the contributions of the different processing steps to the plastic strains. It is shown that the dominant contribution originates from the grit-blast surface preparation step. Contributions purely from the coating process are not distinguishable from that of the grit blasting process within the measurement accuracy. For the as-coated samples no obvious contributions ascribable to the differences in the CTEs of the substrates, or impact related effects are observed.