AC-HVAF supersonic spraying process principle

       The AC-HVAF system is an active combustion high-speed flame spraying system successfully developed by the American TSR (Unique) company in 2001 on the basis of the scientific research results of the Soviet Union after HVOF. It is an emerging method for depositing high quality cemented carbides and metal alloys. The spray particles are heated and accelerated by the air and gas combustion products in the combustion chamber. Fuel gas is propane, propylene, MAPP gas or natural gas. For tungsten carbide-based powders, the particle velocity exceeds 700 m/s and the particle surface temperature is maintained at a temperature about 100 °C lower than the melting point of the metal binder phase, which enables AC-HVAF to work in the "solid particle" spraying mode. Since the combustion temperature of the air-fuel mixture is relatively low when the pressure in the combustion chamber is 3.5Bar~4.5Bar (the maximum temperature of propane combustion is 1850℃, and the maximum temperature of MAPP gas combustion is 1900℃), so the "solid particle" spraying is OK. The oxide content in the coating is very small, and the carbides have basically no thermal degradation, if any, they are very small. AC-HVAF spray coating has good toughness, bonding strength and low residual stress, which can realize the deposition of ultra-conventional thick tungsten carbide coating, super-grinding the coating to the level of optical mirror, which also makes the coating resistant to Fatigue properties are significantly improved.



In addition, due to the high efficiency of the AC-HVAF spraying system (the spraying efficiency of cemented carbide can reach 30kg/h), no oxygen and almost no spare parts consumption, the cost of AC-HVAF spraying carbide is comparable to that of other surface hardening technologies ( It is very competitive compared to casting hard chrome plating and surfacing).



The AC-HVAF system uses the supersonic flame flow formed by the combustion of gaseous fuel (propane, propylene, etc.) and air to heat and accelerate the spray material. The speed of spraying powder particles is higher than that of HVOF system (700m/s ~ 800m/s), but the temperature is lower (1400℃), generally below the melting point. dense coating. The AC-HVAF spray gun is cooled by compressed air.