Study of Cr₂O₃ coatings Part II: Adhesion to a cast-iron substrate

The interfacial indentation technique for determining toughness is applied to plasma-sprayed Cr₂O₃ coatings. In this investigation, another adhesion test, i.e. the four-point bend test coupled with acoustic emission (AE), is performed. AE is monitored during the test from the initiation of load application until fracture in order to detect the damaging of the coating and to identify the different crack growth proc-esses. The residual stresses of coatings are determined by a step-by-step hole drilling method. Correlation of the residual stresses and the two determined parameters to failure (crack length in the case of indenta-tion test and failure displacement in the case of bending test) is discussed. © 1995, ASM International. All rights reserved.