The spray and fuse process consists of two steps. First, the spraying/application of the coating material with either low velocity combustion flame, or by standard HVOF/HVAF.
The coating material (in powder form) is fed into the flame where it is heated and projected to the substrate.
During the second step, the coating is fused to the substrate by torch or vacuum furnace, which densifies the coating, and produces a full metallurgical bond.
The spray and fuse process results in an absence of interconnected pores in the coating and very high bond strengths.
The typical chemical composition of spray and fuse coatings are based on Ni or Co and may include WC or other hard phases for additional wear resistance. Typical hardnesses range from HRC 30-75.
These coating are particularly useful against aggressive wear problems in corrosion environments such as valve components in severe service.