Simulation of chromized coating processing and microstructure

Processing-microstructure relationships of chromized coatings were studied with the help of a model system in which an electrodeposition technique was used to deposit chromium on the top of a Fe-0.2%C substrate instead of using a conventional pack-cementation method. Diffusion studies were conducted at a chromizing temperature of 1000 °C and the effect of cooling rates and heat-treatment times were studied. It was found that a chromized microstructure is predominantly caused by slow cooling. The thermal cycle above the eutectoid temperature is important in controlling the coating microstructure. Voids typically formed in the chromized coatings are not due to the Kirkendall effect or halide activators. However, a vacancy-interstitial interaction might explain their formation.