Influence of residual stress on the wear resistance of thermal spray coatings

Thermally sprayed coatings are widely used for wear protection. Their wear resistance depends on coating properties such as the microstructure, hardness and porosity etc. but also on the residual stress in the coating. It is induced by a variety of influences e.g. temperature gradients, difference of the thermal expansion coefficient of the coating / substrate materials and the geometry of the components.

In this work, the residual stress was determined by using hole-drilling method and X-ray diffraction. Pin-on-Disc and Pin-on-Tube tests were used to investigate the wear behaviors. After the wear tests, the wear volume was measured by using a 3D-profilometer. The result shows that the strength of the residual stress can be controlled by varying the coating thickness and the surface geometry. The wear resistance is significantly positively influenced by the compressive stress in the HVOF WC-Co coatings and negatively affected by the tensile stress in Twin-Wire-Arc-sprayed FTC-FeCSiMn coatings.