A Most Demanding Job
According to Bob Hill President, Solar Atmospheres of Western PA recently partnered with a customer for one of their most demanding jobs ever attempted. The customer was searching for a facility that could process sixteen bars weighing a total of 10,693 pounds to be vacuum thermally processed at 2500±12°F for 168 hours (7 days).
This recrystallization anneal cycle was to be performed on extruded rounds made from a special nickel base alloy. Due to the length of the thermal cycle, it was the customer's intent to process all sixteen of the 6.625" round bars together in one layer, while maintaining a minimum of 3.5" spacing between the bars. Since at high temperature the material would have a tendency to warp severely, Solar decided to use a flat 2.5" thick graphite hearth base plate 54" wide x 248" long. Cognizant of the nickel/carbon eutectic temperature of 2130°F, Solar knew that an interfacing material would be imperative for the success of the run. Therefore, it was decided to use four 1" think ceramic blankets rated at 2600°F as separation.
The furnace was operated at 0.5 torr partial pressure flowing nitrogen and ramped at 600°F per hour to 2000°F. Once at 2000°F, held for one hour, the ramp rate was slowed to 300°F per hour to the 2500°F temperature. Upon completion of the 168 hour hold, the furnace was cooled to ambient in static nitrogen and opened. The ceramic blankets did their job and there was no evidence of eutectic reaction. The pyrometry of the furnace was exact as there was no evidence of insipient melting of the alloy. The vacuum furnace's robustly designed hot zone, which included multiple layered graphite felt insulation and graphite elements, looked immaculate.
This exotic material will be used for a 2000°F rotating application. The vacuum recrystallization anneal was the most critical step in the manufacturing process for the ultimate properties required.
Bob Lacock, Marketing Manager
Solar Atmospheres, 800.347.3236 x 213
rdl@solaratm.com
