Adhesion evaluation of multilayered based WC–Co–Cr thermally sprayed coatings

This paper describes the adhesion evaluation of different interlayers such as Co–Cr, Ni–Cr 80–20 HVOF (High Velocity Oxy-Fuel) thermally sprayed coatings and Ni-plating between the cermet based WC–Co–Cr coatings. Three adhesion measurement methods for these different multilayered based thermal spray coatings, namely tensile adhesive strength (according to EN 582), interfacial indentation and solid impact tests were conducted. The distinguished coating properties include: i) the adhesive strength, ii) the interfacial toughness, iii) the depth of impact. The metallographic and experimental results show that the electrochemically deposited interlayer Ni-plating provides the highest adhesion to cermet coating within the multilayered structured coatings. This is not only due to the chemical affinity between the Ni-plating and the cermet coating, but also to its homogeneous microstructure, since the electrochemically deposition does not provide splat formation.