**7.3 Detonation flame spraying**

By the term "detonation" is meant a very rapid combustion in which the flame front moves at velocities higher than the velocity of sound in the unburned gases, and therefore characterized as supersonic velocities. A precisely measured quantity of the combustion mixture consisting of oxygen and acetylene is fed through a tubular barrel closed at one end. In order to prevent the possible back firing a blanket of nitrogen gas is allowed to cover the gas inlets. Simultaneously, a predetermined quantity of the coating powder is injected into the combustion chamber. The gas mixture inside the chamber is ignited by a simple spark plug. The gas mixture combustion generates plume which melt the particles to form coating (**Figure 20**).
