MANDREL-COATING INTERACTIONS IN HVOF THERMAL SPRAY FORMING PROCESSES

摘要

Thermal spray processes are used to produce coatings on a substrate changing its surface properties. Thermal spray forming processes are based on the spraying of a coating material onto a removable mandrel. These kind of processes produce self-standing shapes of the sprayed material in "Near Net Shape" processes. The Thermal Spray Center of the University of Barcelona has developed a high velocity oxyfuel (HVOF) forming process to obtain wear resistant components. The materials chosen are CERMET (WC-Co) and NiCrBSi blends. The use of a easy removable mandrel allows the study of the interactions between the sprayed material and the substrate material by direct observation of the mandrel's surface after removal. Results clearly show that there is a plastic deformation on the steel substrate due to impact of the ceramic component of the CERMET. This type of interactions has some influence on the adherence of the coating, affecting the reproducibility of the forming technique. Results also show the perfect reproducibility (at the micron scale) of the surface details of the mandrel in the contact face of the self-standing form.