Study of Cr2O3 coatings .1. Microstructures and modulus

Metallographic characterization has been used to estimate the quality and, particularly, the adhesion of plasma-sprayed Cr2O2 coating. This study focuses on the state of the substrate before spraying, During the process of spraying, the differential contraction generated between the various materials because of their different physical and mechanical properties determines the stresses inside the coating and at the interface between the coating and the substrate. The residual stresses thus influence the mechanical and thermomechanical behavior of the coated parts and their adhesion. These stresses are determined by a step-by-step hole drilling method (Part ZI of this paper), and Young's modulus is measured by two different methods: a dynamic ultrasonic test and a static four-point bend test, Part II of this paper is devoted to the adhesion of a Cr2O3 deposit on a cast iron substrate.