Effect of the spray parameters on the particle behaviour and the coating properties during ID warm spraying of fine WC-12Co powders (-10 + 2 µm)

Internal diameter (ID) coating by means of thermal spraying for the wear and corrosion protection of components is currently experiencing growing interest in science and industry. While high-kinetic spray processes (such as HVOF, HVAF or warm spraying) in combination with cermet materials (e.g. WC-Co or Cr₃C₂-NiCr) are well established for this purpose in traditional (external) coating, they have hardly been used in the ID area so far. Even though a few special ID spray guns with compact design and low combustion energy are by now available on the market, only little is known about the effects and interactions of the spray parameters on the particle behaviour and the coating properties. Due to the mentioned gun specifications and the usually required short spray distances for ID coating, fine spray powders < 15 μm must be used to ensure sufficient melting and acceleration of the particles. In this study warm spraying of fine WC-12Co powders (-10 + 2 µm) using a novel spray gun “ID CoolFlow RED” (Thermico, Germany) was investigated. Statistical design of experiments (DoE) was employed to analyse and to model the influence of varying spray parameter settings on the in-flight particle behaviour and the corresponding coating properties.