Abradable Coatings used for Gas Path Seals in Turbine Engines
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.
Abradable Coatings for Gas Path Seals in Turbine Engines
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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
VAC AERO Brazes 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. 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.
Joining Aluminum for Airborne Electronics
by J.E. Pritchard & R. Laub
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.
Vacuum Furnaces for Brazing of Aluminum
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Because of its light weight and good thermal conductivity, aluminum is often the material of choice for assemblies that house or cool 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 Participates in a Study About Building Lean Supply Chains
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.
