High tensile adhesive strength NiCrMo coating enabled by plasma-spraying a Mo-clad NiCr powder for reliable bond coat application

Metal bond coats have been widely applied to thermally sprayed ceramic coatings to increase the adhesion. However, even the bond coat depends on mechanical bonding with a low adhesive strength. In this study, a novel metal bond coat with both high adhesion and cohesion is proposed by plasma-spraying Mo-clad Ni-based. To reveal the bonding state, NiCrMo splats were deposited on five metallic substrates including Ti alloy, mild steel, stainless steel, nickel-based alloy and Al alloy. The morphologies of the splats were characterized by scanning electron microscopy (SEM) and laser confocal microscopy. The interface samples were prepared with focused ion beam (FIB) cutting and the bonding was estimated by scanning electron microscopy. The adhesive strength was tested by the tensile test with the modified coating samples by reducing load-bearing area from 40 % down to 10 % as compared that for the conventional tensile adhesion test (TAT). Results show that with the fully molten NiCrMo particles of temperatures higher than 2620 °C metallurgical bonding can be formed for all substrates. The measurement by the modified TAT yielded the mean tensile strength from 130 MPa to 150 MPa, which are the highest compared to conventional metal coatings. The present results reveal that the APS NiCrMo coating can be used as an effective bond coat which can be applicable to a wide range of different substrate materials.