Evaluation of adhesion strength between amorphous splat and substrate by micro scratch method

A micro scratch test was performed to evaluate the adhesion strength of plasma sprayed Fe-based amorphous splats deposited on a mirror polished steel substrate preheated at different temperatures. The lateral force (LF), penetration depth (PD) and acoustic emission (AE) signals were recorded to reflect the dislodging process of the splats. The debonding mechanism and the adhesion strength of the individual splat were discussed in details. The results indicate that the adhesion strength of splat was prone to be higher on fully preheated substrate due to sufficient spreading time and good wettability at the droplet/substrate interface. The scratch process contains three stages, i.e., scratching on the bare substrate towards the splat (stage I), contacting and dislodging the splat (stage II), moving away from the splat (stage III). The maximum lateral force (MLF), PD as well as AE signal in stage II vary a lot both in value and range of influenced distance with the increment of substrate preheating temperature. The projected cone areas and residuals onto the scratch can qualitatively reflect the bonding status of splat, whereas the ratio of adhesion force to splat area can quantitatively characterize the adhesion strength of the splat.