A Most Demanding Job
According to Bob Hill, President, 麻豆国产精品 of Western PA recently partnered with a customer for one of their most demanding jobs ever attempted. 聽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掳 卤12掳F for 168 hours (7 days).
This recrystallization anneal cycle was to be performed on extruded rounds made from a special nickel base alloy. 聽Due to the length of the thermal cycle, it was the customer鈥檚 intent to process all sixteen of the 6.625鈥� dia round bars together in one layer, while maintaining a minimum of 3.5鈥� spacing between the bars. 聽Since at high temperature the material would have a tendency to warp severely, Solar decided to use a flat 2.5鈥� thick graphite hearth base plate 54鈥� wide x 248鈥� long. Cognizant of the nickel/carbon eutectic temperature of 2130掳F, Solar knew that an interfacing material would be imperative for the success of the run. 聽Therefore, it was decided to use four 1鈥� think ceramic blankets rated at 2600掳F as separation.
The furnace was operated at 0.5 Torr partial pressure flowing nitrogen and ramped at 600掳F per hour to 2000掳F. 聽Once at 2000掳F, held for one hour, the ramp rate was slowed to 300掳F per hour to the 2500掳F temperature. 聽Upon completion of the 168 hour hold, the furnace was cooled to ambient in static nitrogen and opened. 聽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. 聽The vacuum furnaces 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掳F rotating application. The vacuum recrystallization anneal was the most critical step in the manufacturing process for the ultimate properties required.