It is the use of heat the coating material is heated to a molten or semi-molten state, and then by means of the flame stream and high-speed.
The gas particles are sprayed onto the coating material the substrate surface, thereby depositing a coating of a certain special features
Twentieth century the 1980s, there has been a first-generation HVOF equipment Jet-Kote;
Particle velocity up to 400m / s or more;
Coating greatly improved bond strength, porosity greatly reduced;
Flame temperature <3000 ℃, the carbide coating small decomposition process;
Aviation kerosene instead of using propane, propylene and oxygen to reduce the cost;
In recent years the use of compressed air instead of oxygen HVAF equipment, tungsten carbide coating better performance.
Low degree of oxidation, tungsten carbide carbon loss near vacuum spraying;
Strength approaching sintering / casting material;
High hardness, good toughness;
Excellent polishing performance, can be polished to a mirror;
High production efficiency, metal 20Kg / h, tungsten carbide 30-40Kg / h;
Spraying process does buildup.
Environmental requirements: Cr6 + carcinogenic, electroplating wastewater pollution.
Some of the requirements for high temperature, corrosion and wear conditions, can not meet the requirements:
The presence of microcracks in hard chrome plating;
The presence of hydrogen embrittlement of hard chrome plating;
Deposition plating process is slow (about 25μm / hour), long process cycle;
Plated workpiece size is limited dimensions of the plating tank;
Cost factor: For larger size, requires coating of the workpiece, the cost is relatively high;
The higher environmental requirements, waste discharge costs.
In recent years, countries have carried out research into alternative hard chromium plating.
Among the many methods, HVOF made a major breakthrough,
Substantially overcomes the aforementioned problems of hard chrome plating,
Get a wider range of applications.