Mechanical properties of thermal sprayed substrates

Thermal spray coatings are used for many applications where improvement of surface properties is required. The use of thermal sprayed coatings is limited in applications requiring structural strength and particularly where components are fatigue limited. The present paper looks at the mechanical properties of Ni-20Cr coatings deposited on SS304 & mild steel substrate. Ni-20Cr coatings were deposited using HVOF spray, APS and cold spraying. Low cycle fatigue measurements were done on coated substrates followed by characterization of the fracture surface to understand fatigue crack origin and propagation. Microstructure characterization of the as-sprayed coatings, including residual stress measurements was done to understand the mechanism underlying the fatigue behavior. The results are discussed in terms of the spray process used and the key factors affecting LCF capability.