Thermal spray processes like air plasma spray and High Velocity Oxygen Fuel (HVOF) are usually thought of as being used primarily for applying protective coatings to new parts. While new part applications do indeed constitute the majority of their use, there are also a wide variety of repair techniques that employ thermal spray processes. VAC AERO has been a leader in developing repairs for aircraft structural components and gas turbine engine parts using thermal spray processes. An example of a structural component repair involves a flap track from a popular turbo-prop aircraft.  As the wing flaps of this aircraft are extended and retracted during landing and take-off, rollers run along the surfaces of a series of components known as flap tracks.

Kalisz, Poland (March 28, 2008).

In the last 15 years Poland has seen considerable direct investment by American, Canadian, and Western European aerospace companies. During the pre-1990 Soviet years, Poland was one of the main centers of Soviet Bloc aerospace activity. After the collapse of the Soviet Bloc, Polish skilled labor and engineering resources, experienced and competitively priced, were underutilized. Since the entry of several large companies (Sikorsky, Pratt & Whitney Canada, Pratt and Whitney America, EADS, Goodrich, and others) in this region, special processes became one of the bottlenecks of the Polish aerospace market.

The purchase of a vacuum furnace involves a considerable capital investment. As a result, the question of buying a used furnace at a lower cost than a new furnace is a fairly common one. However, there are a number of potential issues with used equipment that should underscore the warning “buyer beware”. To begin with, good used vacuum furnaces are a rare commodity. When they do appear on the market, they don’t last long. Many of the best are purchased through industry networking and never reach the general market. Still, there are numerous dealers of used furnace equipment with inventories posted on their websites.

By J.E. Pritchard, S. Rush, A. Kiela

VAC AERO International Inc.

Abstract

Application of sacrificial coatings has long been used to reduce rotor-shroud clearances in gas turbine engines. Materials normally used for these coatings include sintered metal-powder segments, sintered metal-fibre segments, metallic honeycomb (filled and unfilled), elastomers and thermally sprayed abradable coatings. Thermally sprayed coatings offer advantages over the other materials, including direct application, easy removal and repair, variety of coating materials and good performance. New abradable thermal spray coating materials have been developed for performance in industrial turbine engines at operating temperatures up to 980ºC. Results are presented from laboratory evaluations of these coatings by burner rig and hot abradability testing.

For maximum fuel efficiency, many gas turbine engine designs depend on sacrificial coatings to tighten internal clearances between moving parts. An extra gap of .005" between the rotating blades and the engine casing can increase fuel consumption by as much as 0.5%. As fuel comprises more than half of direct operating costs, this waste can be significant. Engine efficiency largely depends on close clearance between blades and casing. Clearance can be affected by a number of engine operating variables, including casing expansion and contraction, loading due to maneuvering, thrust, gust, stall, vibration and manufacturing tolerances. An industrial turbine engine manufacturer was experiencing unsatisfactory results with the ring segment coatings used to maintain rotor-shroud clearance. Because of poor abradability, the coatings caused excessive wear on the tips of the turbine blades. The engine manufacturer and VAC AERO agreed to work cooperatively to develop an improved abradable coating for these applications. Read More

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. These complex assemblies often are manufactured from numerous individual components that must be joined. There are many ways to join aluminum including mechanical fastening (screws, rivets, etc.), adhesive bonding, welding and brazing. The selection of a joining process must be based on a careful analysis of the service requirements and the materials involved. 

VAC AERO’s Coatings division recently received six new approvals from Rolls-Royce Canada for thermal spray and inorganic paint coatings. The facility was qualified to the stringent standards of RPS 300, 392 and 427 for plasma spray coatings and RPS 666, 666/1 and 666/4 for inorganic paint coatings. Beginning in February 2008, these coatings will be applied to large compressor casings for industrial turbine engines.

For more information on VAC AERO’s Coating Services please click here.

VAC AERO provides custom furnace designs and process capabilities to suit your specific requirements.

In addition to standard vacuum heat treating and brazing furnaces, VAC AERO also manufactures custom vacuum systems for a wide variety of special processing applications. VAC AERO’s skilled team of engineers works closely with the customer from concept through design, final manufacture and installation. VAC AERO designs and builds standard Gas Quench furnaces for maximum durability, reliability and trouble-free operation and provides an outstanding level of training, field and technical support based on decades of commercial heat treating experience.

A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   Sa-Sq   St-Sy   T   U   V   W   X   Y   Z   stabilizing treatment (1) Before finishing to final dimensions, repeatedly heating a ferrous or nonferrous part to or slightly above its normal operating temperature and then cooling to room…

Read More

A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   Sa-Sq   St-Sy   T   U   V   W   X   Y   Z   zinc worms Surface imperfections, characteristic of high-zinc brass castings, that occur when zinc vapor condenses at the mold/metal interface, where it is oxidized and then becomes entrapped in…

Read More