High velocity oxygen/air fuel process (HVOF/HVAF)

Purpose:

• hard-alloy wear-resistant coatings based on tungsten carbide;
• application of heat-resistant coatings;
• corrosion and wear protection;

Customer Benefits:

• high speed of sprayed particles, due to which the obtained coatings have high density and high adhesion strength;
• the process occurs with relatively little thermal exposure to the substrate;
• ecological clean process, used as a replacement for galvanic chrome plating;
• coating spraying with minimal allowances for subsequent machining;
• high efficiency and repeatability of process characteristics owing to works automation.

The HVOF method was based on two previously developed methods: detonation and gas flame. In the detonation method, as in gas flame, acetylene is mixed with oxygen, and then this combustible mixture is mixed with a transporting gas (nitrogen) and a coating material. 

    Metal powder particles are accelerated to a speed of 750 m/s. The distance between the surface of the spraying part surface and the nozzle cut is 100... 120 mm. In this case, combustible gas reaches a temperature of 2700 ° C.

The advantage of the high-speed gas-flame method HVOF/HVAF compared to other spraying methods is the sufficiently high particle velocity (up to 750 m/s) and the minimum porosity of the resulting coating.

The purpose of the HVOF/HVAF method is to combine a continuous process characteristic of the gas-flame method with a relatively high coating quality, as in detonation spraying.

Advantages of the HVOF/HVAF method:

• obtaining a coating with minimal porosity (< 1%) in combination with high adhesion strength to the base material (80 MPa or more);

• due to the low roughness of the sprayed surface, there is practically no need for its subsequent machining (or required to a minimum);

• thermal impact on the part is minimal.

Application:

• aerospace;
• drilling;
• oil and gas;
• chemistry and rewinding;
• metallurgy;
• energy.

Application by parts:

• strengthening and restoration of pumps, smoke sinks and turbines shafts;
• gas thermal coatings as a replacement for galvanic chrome plating;
• tungsten carbide coatings for reduction and protection against wear of rods;
• repair of coating and spraying on new plungers, bushings, pistons, etc.;
• restoration and protection against wear of new housings of submersible electric motors (PED), rotors of rotary engines;
• high-speed spraying of housings, covers (reduced share of flushing, erosion, reduced losses), impellers (increased operating life) of pumping equipment;
• restoration and protection against wear of operating elements of shutoff valves;
• repair of babbit bearing coating;
• restoration and strengthening of turbocompressor rotors by gas-thermal spraying;
• spraying of brake rollers of drawing drum and rollers of rolling mills with wear-resistant hard-alloy coating.