Technically speaking flame spray is not the same as detonation gun coating.
Jim is taking advertising liberties here.

Paul Lamar

There are a number of thermal spray processes. It's been a few years since I was heavily involved, but the ones that I am aware of include:

Flame spray: an alloy is introduced to a flame (like an oxy-acetylene torch) via powder or wire feed, and is essentially brazed to the parent metal. Bond strength isn't very good, and the density and uniformity of the coating is not very good.

Plasma spray: A gas is superheated with an electric arc in a torch, and a powdered alloy is introduced into a nozzle, thus melting the material and imparting a relatively high velocity. The bond is better than flame spray, since it is both metallurgical and somewhat mechanical.

Detonation gun: fuel and air are mixed in a nozzle and detonated via a spark. This is an intermittent (albeit rapid) deposition method. The powdered alloy is introduced to the expanding and hot gas in a nozzle, and supersonic particle velocities are achieved. The coating goes on in "splats" about the size of a nickle.

High Velocity Oxy-Fuel: Similar to d-gun, but a continuous process.

All the methods yield highly variable results depending on how carefully the numerous parameters are controlled -- powder grade, fuel rate, feed rate, distance to workpiece, speed of motion of part, etc, etc. The fuel type and mixture strength affects the alloy composition (size and pct of retained carbides, inclusions, porosity). The choice of vendor has a tremendous amount to do with the results. There are also many, many powder compositions to choose from.

Jon Lauter
Rotary Power Marine Corporation

Thanks Jon.

Paul Lamar
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