Investigation of Mechanical Properties of Twin Wire Arc Repair of Cast Iron Components

Twin wire arc is a commonly used thermal spray technology for application of steel coatings to cast iron components. Adhesion strength is a critical property of such coatings and significant research is available reporting adhesion strength following test procedures similar to ASTM C633. However, residual stresses and the anisotropic structure of the coatings leads to significantly different behavior in bending applications than in the purely tensile loading of the standard adhesion test. This work seeks to relate the pull-off adhesion strength to the bending strength of a coating and to characterize the failure modes of coatings in both static bending and bending fatigue. Non-destructive evaluation systems were used to monitor crack growth and disbonding during bending tests. Comparisons between bend tests and pull-off adhesion tests show significant differences to consider when evaluating twin wire arc coatings. Additionally, in many applications the wear properties of a coating must be understood. This study seeks to relate the wear resistance of coatings to their microstructural properties. Reciprocating and abrasive wear testing showed that wear behavior is highly dependent on the spray parameters used during the coating process.