**7. Types of thermal spray processes**

There are various types of thermal spray coating processes introduced by the researchers (**Figure 17**).

#### **7.1 Powder flame spraying**

In powder flame spraying, the feedstock material is injected to the plume for heating and melted by the heating zone. After melting the molten particles are propagated towards the substrate surface. Then the molten particles are deposited on the substrate surface or pre-deposited splat to form a coating (**Figure 18**). The molten particles are ejected by the flame spray gun. The only difference between powder flame spraying and wire flame spraying is the feedstock material.

**Figure 17.** *Classification of thermal spray coating process.*

**Figure 18.** *Powder flame spray technology.*
