Effect of substrate temperature on coating adhesion

grantor: University of TorontoAn experimental study was conducted to study the effect of preheating stainless steel specimens before depositing nickel coatings with a D.C. plasma torch. Substrate temperature was varied from 25°C to 650°C. The adhesion strength and the porosity of the coating were respectively measured using a standard ASTM C 633-79 pull test and a mercury intrusion porosimeter. Coating microstructure was examined under a SEM. Oxide layer formed on the test specimens during heating was analyzed using XPS and argon ion sputtering. The adhesion strength of the coating increased from 10 MPa to 75 MPa when substrate temperature was raised from 25°C to 650°C. Heating substrate slows the solidification rate of impinging particles, allowing them to make better contact with the substrate, and also produces an oxide layer on the substrate surface which can change its thermal contact resistance and wettability. Oxide layer thickness increased with substrate temperature.M.A.Sc