AC-HVAF/SAF powder spraying equipment is used for the application of coatings from carbide, pure metal and metal alloy powders for the protection of parts, machines, vessels and structures from abrasive wear, erosion and chemical corrosion.

The service life of parts can be extended by several fold, and in some cases by as much as 10 times, by applying appropriate AC-HVAF/SAF protective coatings. As an example, consider downhole pipes used in the oil drilling industry, which at times experience severe corrosion. In an effort to improve the typical service life (of about 3 weeks) a number of solutions were explored. Conventional HVOF coatings yielded only a moderate improvement, as comparatively high posority and poor bond strength led to eventual peeling of the coatings. However, the same material applied with the UltraCoat™ powder spraying system produced a stress-resistant coating with much higher bond strength and nearly zero porosity, increasing the service life of the pipes from about 3 weeks to well over a year. That is a dramatic difference that resulted in substantial cost savings, and is one of many examples from different industries where use of appropriate coatings has made a real difference.

We offer two systems for powder spraying:

• M3™ Supersonic Spray Gun with UltraCoat™ Supersonic Air Fuel system.
  
  


• M2™ Spray Gun with Quasar™ AC-HVAF system.
  
  

AC-HVAF "High-Velocity Air-Fuel" process is used for deposition of hard coatings from carbide, pure metal and metal alloy powders. AC-HVAF equipment runs on compressed air and a fuel gas such as propane, propylene, MAPP gas or natural gas. While similar to HVOF in principle, there are several key differences. Air is used instead of compressed oxygen, which allows the system to operate at lower temperatures, harnessing all the advantages of solid state particle spraying (similar to Cold Spray). In turn, coating oxide content is also reduced to Cold Spray levels, and the produced coatings contain compressive residual stresses. Use of compressed air also eliminates the need for oxygen tanks, thereby reducing costs.

Occupying a band in between Cold Spray and HVOF, AC-HVAF can produce coatings of equal (in many cases, better) quality while reducing the complexity and cost of coating application. There are several other factors that make AC-HVAF technology exceptionally competitive in many industries, often making it the preferred choice for deployment. Briefly, they are summarized below:

• High Wear Resistance
  One of the main advantages of AC-HVAF coatings is the exceptional wear resistance. In independent studies carbide coatings (particularly WC) have repeatedly outperformed other processes in direct comparison for wear, typically showing a multifold improvement (e.g. three fold improvement over Super D-Gun in ASTM G65), in part due to a substantial reduction in decarburization of carbides.
• High Fatigue Resistance
  AC-HVAF coatings are more fatigue resistant compared to their HVOF counterparts and possess a very high tensile bond strength. The unique coating structure of AC-HVAF prevents crack propagation and delamination. In a comparative study commissioned by the US Air Force to evaluate the use of hard coatings on landing gear as hard chrome replacement, AC-HVAF was directly compared to 5 other processes including Cold Spray. AC-HVAF coatings were the only ones to pass all 10 stress tests, earning the final recommendation.
• High Deposit Efficiency
  AC-HVAF is capable of achieving deposit efficiency of up to 85% for metals, and up to 72% for carbides. Higher D.E. reduces costs as more powder bonds to the part and less powder is wasted.
• High Spray Rates
  In some applications it is economically important to be able to coat large surfaces quickly, and in terms of spray rates AC-HVAF stands in a league of its own. Spray rates of up to 66 pounds (30 kg) per hour for carbides and up to 50 pounds (23 kg) per hour for metals make AC-HVAF an exceptionally efficient process for large scale applications.
• Low Operating Costs
  AC-HVAF requires neither the compressed oxygen of HVOF, nor the expensive gases of Cold Spray. Common fuel gas such as propane, propylene, MAPP gas or natural gas is used in conjunction with compressed air provided by an air compressor (400 CFM, 125 PSI).
• Low Cost of Deployment
  The AC-HVAF system is completely self-contained and requires no peripheral equipment such as independent cooling systems or oxygen tanks. All that is needed for operation is compressed air and a fuel gas, either propane, propylene, MAPP gas or natural gas.
• No Nozzle Clogging and No Frequent Maintenance
  UniqueCoat's proprietary spray gun design does not suffer from nozzle clogging, nor does it require routine replacement of consumable parts, allowing spray jobs to proceed with no interruptions for long periods of time. Additionally, non-clogging nozzles never suffer from "spitting" of accumulated material onto the sprayed surface, making AC-HVAF the preferred choice for coating extremely large parts, such as paper and film rolls, where having 100% uniform and defect-free coatings is paramount.
• Ease of Use for Operators
  The equipment is simple to use and very user friendly. A touch screen interface makes the system easy and intuitive to operate, and intelligent industrial control automatically maintains all operating parameters, instantly shutting the system down if any problems occur. There is no need for extensive configuration or operator training. The system is also very tolerant of operator errors.
• Diversity of Applications
  AC-HVAF can apply all standard HVOF materials, often improving coating quality while delivering higher spray rates, reducing operating costs and eliminating maintenance-related downtime. For these reasons AC-HVAF has become the equipment of choice for many industries worldwide, including automotive, aerospace, steel, paper, film production, power generation, oil, coal, and many others. The AC-HVAF system has earned a reputation for coating quality, reliability and simplicity of use.
• Hard Chrome Replacement
  Hard chrome plating has come under scrutiny because of its environmental hazards. The plating process produces hexavalent chromium, a known carcinogen. Environmental regulations are becoming increasingly strict, putting pressure on chrome plating shops to invest in new equipment or shut down. Because of this, the price for hard chrome is increasing while availability is decreasing.
  
  AC-HVAF is an excellent “green” alternative to hard chrome plating. There are no hazardous fumes to contain, and the overspray can be recycled. UniqueCoat Technologies offers several materials which can replace hard chrome plating. These materials provide much better wear protection and other enhanced properties. They also have the advantage that they can be applied in a targeted area as needed in order to minimize the application cost.
  
  Coatings of the most popular Tungsten Carbide-based compositions are applied onto roll surfaces and superfinished to better than Ra 0.3 micro-inch roughness. Such surface quality became possible due to the superior density of AC-HVAF coatings and the absence of brittle phases which are usually formed due to oxidation and thermal deterioration of carbides in other thermal spray processes.
  
  AC-HVAF WC-based coatings are noticeably harder and denser than hard chrome, exhibit better toughness and corrosion resistance, and can be applied to practically any thickness, providing armor-like performance during service. Contact us today to discuss your application. We will suggest a coating material to meet your needs.

AC-HVAF stands for Activated Combustion High Velocity Air Fuel. In technical definition, HVAF technology is a derivative of HVOF. Instead of using compressed oxygen the system extracts oxygen from air. This eliminates the need for compressed oxygen, reducing costs, and also allows the system to operate at lower temperatures, harnessing all the advantages of solid state particles (the same principles used in Cold Spray). The oxide content is also reduced to Cold Spray level. Activated Combustion is a patented improvement to the HVAF process developed by Dr. Baranovski in the 1990's. It opened a second era of HVAF-based equipment that no longer suffered from the poor deposit efficiency of its predecessors. This, along with many other changes, allowed modern AC-HVAF to be become a viable technology with many practical advantages over conventional HVOF and Cold Spray systems.


Supersonic Air Fuel (SAF) is a new thermal spray process (patent pending) that is the technological successor to AC-HVAF, producing particle velocities of Mach 3, 1000-1200 m/sec, approximately double the velocity of AC-HVAF. Higher kinetic energy of solid particles produces higher contact pressures upon impinging a substrate, leading to better adhesion to the substrate and cohesion within the coating. The result is a marked improvement in the physical and mechanical properties of the sprayed coatings. For instance, the hardness of WC86-Co10-4Cr coatings applied with agglomerated and sintered powder is increased to over 1400 HV300, a 27-32% improvement compared to AC-HVAF coatings. Electrical conductivity of copper coating applied with SAF exceeds that of coatings applied with Cold Spray. Due to practically non-existent porosity, corrosion resistance of SAF coatings used for hard chrome replacement is actually better than that of hard chrome plating. Supersonic Air Fuel inherits all the advantages of AC-HVAF, while setting a new standard for coating quality.