HVAF High Velocity Air Fuel Surface Grit Blasting Coating Application Applied Coating
M3™ Supersonic HVAF Spray Gun

The M3™ supersonic HVAF spray gun delivers the highest quality cemented carbide coatings. The M3™ can apply all HVOF powders (-45+15 μm), as well as special HVAF cuts (-30+5 μm, -30+10 μm). Metals and metal alloys can also be effectively applied.

The M3™ produces not only high particle velocity, but also high particle temperature, compared to single-nozzle HVAF spray guns. This allows the M3™ to produce impermeable tungsten carbide coatings with hardness of up to 1670 HV300 and negligible W2C content. Standard HVOF cut powders (-45+15 μm) can also be sprayed with hardness of 1350 HV300.

Tungsten carbide and chrome carbide coatings sprayed with M3™ have passed high pressure gas permeability tests at 15,000 PSI, with 100% success rate.

M3™ coatings meet or exceed the coating requirements of Aerospace Material Specification (AMS 2447 Rev. D).

PowderCutVelocityD.E.Spray Rate
WC-based powders-45+15 μm
-30+5 μm
-25+5 μm
960 - 1250 m/s46-62%34 kg/h max
CrC-based powders-25+5 μm~ 1300 m/s40-55%18 kg/h max
Data obtained on Propylene 
  • WC-based coatings with hardness of up to 1670 HV300
  • Coating porosity typically below 0.2%
  • Compressive residual stresses in coatings
  • Negligible oxide content in coatings (1.5-2 times that of feed stock material)
HVAF tungsten carbide based coatings outperform HVOF counterparts by 3-6 fold in slurry erosion tests, and up to 15 fold in cavitation resistance tests. Due to very low W2C content and high bond strength, M3™ applied tungsten carbide coatings also exhibit 5+ times higher impact resistance compared to HVOF.

The M3™ spray gun operates on Propylene or Propane. Highly efficient 100% air cooling eliminates the need for a chilled water supply.

The cost of coating application with M3™ is 2-4 times lower compared to HVOF process due to use of air instead of oxygen and high spray rates that reduce spraying time.
M3™ Spray Gun
Fuel TypesAir ConsumptionCooling
Propylene, Propane 250 SCFM @ 125 PSI100% air cooled
  • Highest quality coatings from cemented carbides
  • Axial powder injection
  • 100% Air Cooling (no water chillers)
  • Can spray continously for hours without stopping
  • Supports use of Natural Gas
  • Low operating cost
  • Low consumption of spare parts
  • Fast start-up
Grit Blasting
The M3™ spray gun can also be used to grit blast parts immediately prior to coating application. By supplying grit to the gun and executing the normal spraying sequence on the robot a part can be grit blasted in place. Hot grit blasting may also be similarly perfomed, by supplying grit to a running gun. This high velocity grit blasting offers 20-50 fold reduction in grit consumption, and up to 15 fold reduction in blasting time. For example, a mandrel that normally takes 30 minutes to grit blast, can be hot grit blasted in just under 2 minutes. Hot grit blasting technology permits to substantially increase the bond strength of subsequently applied coatings. For example, bond strength of Inconel 718 was measured to be 29,000 PSI (200Mpa). Grit options include Aluminum Oxide # 120, 150, 180 or 220, as well as Tungsten Carbide 8-14 µm, 14-26 µm, 26-32 µm.

M3™ Tungsten Carbide Coating