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High Velocity Oxygen Fuel - HVOF

Thermal projection by high speed is based on combustion: the one of a fuel that is generally propene, propilene, natural gas, hydrogen or querosene, with oxygen or air, as a supporter of combustion. Consequently, gases expand towards the outside, which generates a beam supersonic that accelerates particles. Reached temperatures (Tmax,flame is 2860ºC) by particles in the supersonic beam are, generally, minors whom in the case of plasma projection (in addition, time of residence and the thermal interchange also are smaller). But the speed is maximized, gas speeds of 1370 m.s-1 using nitrogen like carrying dust gas, giving denser coverings.

The size of the dust of projection used in HVOF is in a rank of 5 - 45 um and volumes oscillate between 20-80 g/min.  Frequently used distances of projection vary between 150-400 mm.

Some of the strong points of this technique are the microstructural uniformity and, product of the time of residence and the temperature of the beam, the diminished degradation of particles by the temperatures reached. On the other hand, comparatively with other techniques of thermal spray, it displays the adjustment to a greater margin of material bases, limitless size of the pieces to cover, diversity of materials, portable equipment, low costs of application and installation, optimization of parameters (that influence much in the properties of the coverings), faster process, possibility of greater thicknesses and minor volume of remainders, among others. These improvements give HVOF too many applications, like the referring ones to resistance to the wearing down, the corrosion and the high temperature, are most common.

About wear resistance apps, works on Co-WC coatings are remarkable in aircraft industry, on rebuilding and reworking of landing gear, engines, and propellers.