Cold spray AM is a process in which powder particles are accelerated at high speed to deposit on a substrate to make a structure. Cold spray means powder particles are not melted, and thus there is no provision for utilizing high-temperature sources to cause melting. On the contrary, in thermal spray, partially or fully molten drops are used, and thus high-temperature sources such as arc, direct current plasma, radio frequency plasma, flame, etc., are required to melt wire, powder, or rod to make molten drops. The American Welding Society classifies cold spray as part of thermal spray due to functional similarities. In the cold spray, the temperature is increased to 1000 °C, but its purpose is to increase the speed of the gas. It also does not mean the cold spray has nothing to do with the melting—partial melting of powder may happen when the speed of the powder is high and the substrate is at a higher temperature—partial melting will provide metallurgical bonding between powders and the substrate or a deposited layer. Thus, the cold spray deposition is not so cold. It, like a thermal spray process, is not hot enough to be able to melt powders before their deposition. Partial melting or liquid phase sintering also happens when post-processing heat treatment is used to improve properties.