Evaluation of bonding strength between yttria coating and vanadium alloys for development of self-cooled blanket

A laser spallation technique was utilized for measurement of the bonding strength between yttria coating and vanadium alloys. The bonding strength between the alloys containing small amounts of yttrium made by levitation melting method and the yttria coating prepared by vacuum plasma-spray was evaluated to be about 950 MPa. It was not clearly observed the effects of alloying elements on the bonding strength. The strength varied about 100 MPa by specimens and by alloy compositions. Detailed observation of the failure type at the interface indicated that crack formation in the coating reduced the stress at the interface, so that the evaluation might be overestimated. It was demonstrated that application of the laser spallation technique to measure the bonding strength between ceramics coating and base material was useful for the evaluation of mechanical integrity of the coating.