Effect of indenter radius on scratch test of ceramic coating

In order to study effect of indenter radius on scratch test, scratch tests were carried out with three different sizes of diamond indenters and four types of coating materials. The critical load, L_c was increase with increasing of radius of diamond indenter. The maximum shear stress at the interface is obtained by Fem analysis at critical load, L_c with indenter radius of 0.2 mm. This maximum shear stress is considered as an adhesive strength of coating material. Critical loads, L_c under other indenter radius were predicted by FEM analysis. L_c obtained by scratch tests shows good agreement with L_c predicted by FEM except the result of CVD-TiC coating with indenter radius γ=0.4mm. Change of friction coefficient during scratch test may affect on the result.