IMPROVED RING SHEAR TEST FOR THE EVALUATI ON OF ADHESION STRENGTH OF THERMAL SPRAYED COATING

The ring shear test was modified to evaluate the adhesion properties o f plasma sprayed coatings. To ensure the ring shear test to be reliabl e, the conditions of some main factors, such as coating thickness, coa ting width and rod-jig clearance, for the evaluation of the adhesion s trength were evaluated. The results obtained in this research are summ arized as follows: 1) In order to develop the accuracy of the loading exactly along the specimen's axial direction, the loading stress unifo rmity on the coating and the uniformity of the clearance between rod a nd jig, the conventional ring shear test was modified in shapes of bot h the shearing jig and the specimen and the loading manner. Consequent ly, the reproducible results with less scattering were obtained by usi ng the modified ring shear test. 2) To ensure this modified ring shear test as the method to evaluate the adhesion strength of plasma spraye d coating, the necessary conditions of some main factors were evaluate d. It was found that coating width, coating thickness and rod-jig clea rance should be fixed to some moderate values.