Pushing the envelope in seal technology

Research into non-traditional materials increases
the temperature threshold for metal seals

Manufacturers of turbine and rocket engines have an ongoing need to design engines that run at higher temperatures for better fuel efficiency. Until recently, seal materials were limited to 1300-1400°F because of unwanted stress-relaxation at higher temperatures. Engineers at Advanced Products Company, North Haven, CT, have performed extensive testing of their existing seal materials, while simultaneously searching for other high temperature alloys that are not traditionally used for seals.

Stress relaxation studies at 1800°F

For example, Inconel-718, a common metallic seal material, exhibits excellent corrosion resistance and is preciptiation hardenable up to 180,000 psi; however, it loses its properties at a continuous 1100°F and an intermittent 1300°F. Waspaloy's strength is limited to 111,000 psi, but can withstand temperatures up to 1600°F intermittently and 1300°F continuously. Because of the temperature limitations of these standard alloys, researchers focused their attention on high-temperature alloys not previously considered for seal use. Both oxide dispersion strengthened alloys, such as PM1000, MA-956 and MA-754, as well as refractory alloys, such as Mo/Re, TZM, Mo/W and a proprietary composite alloy, were analyzed in the 1600-1800°F range using ASTM E-328 stress relaxation testing. The graph above illustrates results over time at the top of the temperature range.

Having identified several materials with superior stress relaxation characteristics, researchers presented their results to a group of aerospace and turbine engineers attending a NASA Glenn conference. Advanced Products is currently using these materials to develop and test various prototype seals for leading jet engine companies, with a standard product line projected by June.

--SG

For more information: Circle 629 - Advanced Products Company, North Haven, CT, or connect directly to their website via the Online Reader Service Program at http://www.OneRS.net/102df-629