Microstructure-based thermo-mechanical modelling of thermal spray coatings. (15th May 2015)

• Record Type: Journal Article
• Authors: Bolelli, Giovanni; Candeli, Alessia; Koivuluoto, Heli; Lusvarghi, Luca; Manfredini, Tiziano; Vuoristo, Petri
• Is Part Of: Materials & design. Volume 73(2015:Sep.)
• Page Start: 20
• Page End: 34
• Publication Date: 2015-05-15
• Subjects: Thermal spray -- Coatings -- Finite element simulation -- Microstructure based model -- Elastic properties -- Contact simulation; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2015.02.014
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: 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. Abstract: 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 Cr2 O3, 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 Cr2 O3 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 initiation locations as observed by indentation tests, highlighting the relevance of stress concentrations around microstructural defects (e.g. oxide inclusions). Sliding contact simulations between a hardmetal surface and a small spherical asperity reproduce the fundamental processes in tribological pairings. The experimentally observed "wavy" morphologies of actual wear surfaces are therefore explained by a mechanism of micro-scale plastic flow and matrix extrusion.