Microstructure and adhesion of Cr3C2–NiCr vacuum plasma sprayed coatings

Vacuum plasma spraying (VPS) was used to spray a Cr3C2–NiCr coating of ∼ 150, 300 and 450 μm in thickness onto a plain carbon steel substrate, employing a commercially available Cr20Ni9.5C powder. The splat microstructures observed in the coating were found to consist of a NiCr matrix with a predominant Cr3C2 phase, besides Cr7C3 and Cr2O3. The adhesion of the coating to the substrate was evaluated by means of interfacial indentation techniques. It has been found that the interfacial toughness value changes from 7.6 to 10.1 MPa m1/2 when the thickness increases from 150 to 450 μm. Also, it has been found that the parameter Kcao, determined by linear regression from the Kca versus 1 / e2 curve by means of the interfacial indentation model advanced by Chicot et al., has a value of ∼ 9.8 MPa m1/2.