Members of the thermal spray family of processes typically are grouped into three major categories: flame, plasma arc, and electric arc. (Kinetic energy-driven spray, or cold spray, is a recent addition to the family.) Each of these processes encompasses many more subsets, and each has its own characteristic range of temperature, enthalpy, and velocity. These attributes, in turn, develop coating characteristics that are unique to each process, which in simplest terms include coating bond strength, porosity, inclusions (usually oxides), and hardness. Selection of the appropriate thermal spray method typically is determined by:
•Desired coating material
•Coating performance requirements
•Economics
•Part size and portability