No abstract

No abstract

Achieving a balance between low cycle fatigue and creep in alloy 718 critical rotating hardware has become challenging as application conditions become more aggressive and geometries more complex. Optimization of both forge practice and of minor chemistry variations are required to meet this property balance. A review of potential factors influencing creep variation in direct age alloy 718 forgings identified phosphorus level as a statistically significant factor over the range of 50 ppm to 125 ppm. Verification of the findings was accomplished using a series of full scale heats with phosphorus levels targeted to a 90 ppm minimum. Data from the 12 full scale VIM heats, including 104 creep tests from multiple forgings, exhibited an average creep life of 111 hours with Q1 and Q3 distributions of 80 hours and 145 hours, respectively, when tested at 1100F/120 KSI and 0.2% strain. This is an approximate 2X increase in mean life from historical levels. The results of the evaluation show that with an optimized well controlled forge process phosphorus levels above 80 ppm, but below 150 ppm, will improve creep performance of DA alloy 718.

No abstract

No abstract