Microstructure-based thermo-mechanical modelling of thermal spray coatings

• Microstructure-based finite element models simulate the properties of thermal spray coatings.
• Modelled values of orthotropic elastic moduli agree with experimental measurements.
• Compressive stiffening of plasma sprayed ceramics occurs by progressive crack closure.
• Cracks initiate where defects (e.g. oxide inclusions) cause stress concentration.
• Single-asperity contact models reveal microscale stress propagation and plastic flow.

This paper demonstrates how microstructure-based finite element (FE) modelling can be used to interpret and predict the thermo-mechanical behaviour of thermal spray coatings. Validation is obtained by comparison to experimental and/or literature data.Finite element meshes are therefore constructed on SEM micrographs of high velocity oxygen-fuel (HVOF)-sprayed hardmetals (WC–CoCr, WC–FeCrAl) and plasma-sprayed Cr2O3, employed as case studies. Uniaxial tensile tests simulated on high-magnification micrographs return micro-scale elastic modulus values in good agreement with depth-sensing Berkovich micro-indentation measurements. At the macro-scale, simulated and experimental three-point bending tests are also in good agreement, capturing the typical size-dependency of the mechanical properties of these materials. The models also predict the progressive stiffening of porous plasma-sprayed Cr2O3 due to crack closure under compressive loading, in agreement with literature reports.Refined models of hardmetal coatings, accounting for plastic behaviours and failure stresses, predict crack