Fig. 7 shows the scratch test on the deposited Cr coating. At the load of 139.6 N, there is an abrupt change on the Acoustic Emission (AE) signal, which corresponds to the critical load of the invalidation of the deposited coating. The critical load can be considered approximately as the adhesion between the deposited coating and the substrate. As the load increases linearly with the displacement in the x direction, the AE signal changes continuously, which indicates that Retaspimycin the deposited coating has been damaged. From the cross-sectional morphology (Fig. 4(b)), it can be found that the deposited Cr coating is dense and comformal to the substrate. Duradzhy et al. have found that there is electrolyte elemental diffusion into the surface of the electrode during plasma electrolytic heating process . In CPED process, the diffusion of the elements are both inward to the substrate and outward to the coating , so the deposited coating exhibits excellent adhesion with the substrate. The result of the adhesion test is consistent with the observation of the cross-sectional morphology of Cr coating.