Flame spray, also known as oxy/acetylene combustion spray is the original thermal spray technique developed about 100 years ago. It uses the basic principles of a welding torch with the addition of a high velocity air stream to propel molten particles onto the substrate. The coating material can be either a wire or powder form. Often flame spray coatings are fused after being applied to enhance bond strengths and coating density. When the spray stream is passed across the surface of the substrate material, the molten material rapidly cools forming a coating.
The combustion spraying process, compared with others, is relatively low energy and can be used to spray substrates that cannot be exposed to high temperatures. This can help when component distortion and structural damage is an issue. There are two forms of combustion spraying, using powder or wire stock material, each suited to different applications. Combustion spraying can be used to make repairs, improve efficiency and restore dimensions. It is often a cost-effective method when repairs are required to high cost components.