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
Canada FrançaisAccessibility |

Metallography of Superalloys

by

While specimen preparation of superalloys for metallographic examination is relatively straightforward, the metallographer must take into consideration some of the inherent characteristics of these complex alloys, such as high toughness, presence of large amounts of strengthening phase and high corrosion resistance, to ensure getting samples that clearly reveal their complex microstructures.

Superalloys are complex alloys of Fe-Ni, Ni-, and Co-base compositions. Their microstructure can be quite complex due to the potential for a variety of phases that can form in heat treatment or service exposure conditions. This article discusses the use of new metallographic materials to prepare these alloys and the different etchants required to reveal the structure of these alloys properly as a function of alloy composition, heat treatment and microstructural phases. This discussion is limited to iron-nickel and nickel-base alloys, but most of the comments are also applicable to Co-base alloys.

Biography – Dan Kay

Dan Kay’s Biography Dan Kay (BMetEng, MBA), operates his own brazing consulting/training company, and has been involved full-time in brazing for 45-years. He received his Bachelor of Metallurgical Engineering degree from Rensselaer Polytechnic Institute in 1966, and his MBA from Michigan State University in 1982. Dan regularly consults in areas of vacuum and atmosphere brazing, […]

Welding of High Strength Steel Landing Gear Components

by

For many years, VAC AERO has been performing welding and heat treating operations on a landing gear component for a popular turboprop aircraft. Because of the part design, the welding operation, in particular, is complex and challenging and often involves substantial re-work.

In order to minimize the rate of re-work, VAC AERO undertook a comprehensive process review. The review determined that a minor design change could virtually eliminate re-work at welding. The assembly is a five-piece, tubular structure manufactured entirely from 4330V steel. It consists of a hollow tube approximately 1500mm long by 120mm in diameter, two fittings (upper and lower) that are TIG welded to each end of the tube and two backing rings that bridge the gaps between the fittings and the tube during the welding operation. BY JEFF PRITCHARD

Biography – George F. Vander Voort

by

George received his BS in Metallurgical Engineering from Drexel in 1967 – the last class as Drexel Institute of Technology and received their Distinguished Alumnus Award in 2005.  At Drexel he was twice editor-in-chief of the Drexel Technical Journal, including the three years in a row when it was named the number one college technical […]

Vacuum Brazing Techniques

by

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

by

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

by

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