The Detonation gun basically consists of a long water cooled barrel
with inlet valves for gases and powder. Oxygen and fuel (acetylene most
common) is fed into the barrel along with a charge of powder. A spark
is used to ignite the gas mixture and the resulting detonation heats
and accelerates the powder to supersonic velocity down the barrel. A
pulse of nitrogen is used to purge the barrel after each detonation.
This process is repeated many times a second. The high kinetic energy
of the hot powder particles on impact with the substrate result in a
build up of a very dense and strong coating.