Vacaero

Manufacturers of heat treating and brazing vacuum furnaces and controls, complete hot zone and vacuum furnace retrofits, thermal spray coatings, plasma, HVOF and paint coating services.

VAC AERO Service Experience Trust
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Vacuum Brazing Techniques

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Most base metals typically brazed in vacuum furnaces have a natural oxide “coating” that can inhibit the flow of brazing filler metals. 

Conversely, alloys containing appreciable amounts of reactive elements such as aluminum and titanium tend to form oxides at high temperatures which impede the flow of the brazing filler metal.  Many of the nickel-base superalloys fall into this category and the severity of the problem varies depending on alloy composition.  These materials should be brazed at high vacuum levels of 2 x 10-4 torr or better.  There are several reliable techniques for improving the brazeability of difficult to braze materials.  These include brush nickel plating of the joint surfaces, chemical etching techniques to remove aluminum and titanium from a shallow layer at the joint surface and using special aggressive braze filler metals with self-fluxing characteristics. The oxides of the less reactive metals like iron, nickel, and cobalt tend to dissociate (break down) under low pressure and high temperature.  Therefore, alloys such as the 300 and 400 series stainless steels, carbon steels and many tool steels can be successfully brazed in vacuum at relatively high pressures (1 to 50 microns). BY JEFF PRITCHARD

Joining Aluminum for Airborne Electronics

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When joining aluminum for aerospace electronics, brazing often is the most practical choice for creating a continuous all-metal joint interface.

Because of its light weight and excellent thermal conductivity, aluminum often is the material of choice for assemblies that house or cool airborne electronics.

Aluminum’s properties are particularly important in combat aircraft. Weight minimization becomes a major design consideration for many components going into these aircraft. Thermal conductivity is especially important in the electronics packages because of the heat problems created by the dense packing of powerful systems in limited spaces. The complex aluminum enclosures, chassis and heat dissipators used in military avionics systems often are manufactured from numerous individual components, which must then be joined.

Selection of a joining process must be based on a thorough analysis of the service requirements and materials involved. For example, the joint’s mechanical strength properties often are critical. A structural joint usually requires good tensile and shear strength as well as resistance to fatigue from cyclic vibrations. Thermal conductivity of the joint is essential for heat exchangers and heat dissipators.

Electrical conductivity also may be important in some applications. In addition, the service environment must be considered, particularly when the joint will be exposed to temperature extremes, moisture or other corrosive media.
In enclosures, shielding sensitive electronic components from electromagnetic interference (EM!) often is critical. Certain joining processes provide joints with better EMI shielding characteristics than do others. by J.E. Pritchard & R. Laub

Maintenance procedures for vacuum furnaces

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Maintenance procedures and safe working conditions are essential in maintaining vacuum furnaces as is proper preparation of components to be heat treated prior to charging to the furnace. VAC AERO International operates more than a dozen vacuum furnaces in its own heat treating facilities. In addition, it has manufactured hundreds of vacuum furnaces for sale to the global market. Through these activities, the company has gained extensive experience in the care and maintenance of vacuum furnace equipment.

As with any piece of equipment, proper maintenance at regular intervals is essential for long service life and trouble-free operation of vacuum furnaces. The mechanical components in a vacuum furnace require standard maintenance practices (i.e. cleaning, lubrication, etc). However, the successful use of a vacuum furnace depends on the purity and reliability of its vacuum. Additional maintenance activities are required to ensure good vacuum levels in the system. Leaks in joints and contamination of furnace internals will greatly affect operating vacuum levels and the quality of the processing. Leaks are the most time consuming and troublesome of the maintenance items. Small leaks can only be isolated using helium leak detectors. However, by keeping track of where leaks most frequently occur, preventive measures can be taken to minimize the problem. The operating manuals supplied with most furnaces provide detailed information on maintenance and troubleshooting. All maintenance manuals should be read and understood before commencing furnace operation. BY JEFF PRITCHARD

VAC AERO Participates in a Study About Building Lean Supply Chains

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Building a Lean Supply Chain: Lean shouldn’t stop with your company; to be truly lean, you must reach beyond your shop floor.

Companies of all sizes, shapes, and descriptions are attempting to implement lean manufacturing. As a company becomes lean, however, it inevitably runs into constraints imposed by its suppliers and customers, the adjacent nodes of the supply chain in which it operates. The logical next step to becoming lean internally is to try to spread the lean philosophy outward to those immediate trading partners. Sometimes doing so can bring significant improvements, especially when a large company is influencing one or more of its smaller suppliers. At other times it doesn’t work so well, such as when a small machine shop attempts to influence a much larger raw-material supplier.

HVOF Coating Applications for Modern Gas Turbine Engines

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In order to maximize efficiency in modern gas turbine engines, manufacturers have developed methods of obtaining minimal clearance between rotating turbine blade tips and stationary engine casings. One method utilized involves allowing the tips of the turbine blades to wear into a rub tolerant surface on the casing. This ensures that when the blades are fully extended due to centrifugal forces during engine operation, only a minimal leak path will exist for the hot gas across the tips of the blades.

In order to minimize blade tip wear, engine manufacturers are now designing blade tips with wear resistant coatings. VAC AERO has developed an HVOF CoCrAlY coating that fulfills this application.

SiC-Reinforced Aluminum Alloy Coatings Produced by Cold Spray Process

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Metal matrix composites are becoming increasingly popular for industrial applications as diverse as aerospace, automotive and electronics. The composites consist of an alloy matrix reinforced with ceramic particles to enhance mechanical properties. Aluminum alloys are especially popular as a matrix material. The addition of relatively inexpensive silicon carbide (SiC) particles to an aluminum alloy matrix improves strength, elasticity, wear resistance and corrosion resistance. These composites are used widely for high performance structural components in aerospace and automotive applications. Current techniques for fabricating the composites include casting, extrusion, powder metallurgy and thermal spray deposition

HVOF Coatings for Chrome Replacement on Landing Gears

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Hard chromium plating has traditionally been used on aircraft airframe components to provide corrosion protection and wear resistance. Chromium plating has been identified by governmental regulatory agencies as a health hazard due to the presence of hexavalent chromium within the plating solutions. This has prompted major airframe and landing gear manufacturers to search for alternative processes to chromium plating which do not pose a health threat to the process operators. The leading candidate for hard chromium replacement is tungsten carbide coating applied by the HVOF (High-Velocity Oxygen Fuel) thermal spray process. There are many practical considerations to account for when implementing a change of this magnitude.

Canada is the world’s foremost supplier of landing gears. With the U.S. Environmental Protection Agency imposing stricter limits on the use of hexavalent chromium, and other countries considering similar legislation, efforts are underway to adopt a new coating process. “It’s in everyone’s interest to be ready in time for that legislation,” says IAR project director Dr. Jean-Pierre Immarigeon. “If new technology can be mastered, you can adopt it in advance of the legislation being passed.” The best clean alternative technology being considered by the aerospace industry is a ceramic/metal composite coating applied by High-Velocity Oxy-Fuel (HVOF), a thermal spraying process that is environmentally safer than chrome plating and has the potential for cost and time savings.