Fatigue crack propagation of nickel-base superalloys at 650 deg CThe 650 C fatigue crack propagation behavior of two nickel-base superalloys, Rene 95 and Waspaloy, is studied with particular emphasis placed on understanding the roles of creep, environment, and two key grain boundary alloying additions, boron and zirconium. Comparison of air and vacuum data shows the air environment to be detrimental over a wide range of frequencies for both alloys. More in-depth analysis on Rene 95 shows at lower frequencies, such as 0.02 Hz, failure in air occurs by intergranular, environmentally-assisted creep crack growth, while at higher frequencies, up to 5.0 Hz, environmental interaction are still evident but creep effects are minimized. The effect of B and Zr in Waspaloy is found to be important where environmental and/or creep interactions are presented. In those instances, removal of B and Zr dramatically increases crack growth and it is therefore plausible that effective dilution of these elements may explain a previously observed trend in which crack growth rates increase with decreasing grain size.
Document ID
19880048681
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Gayda, J. (NASA Lewis Research Center Cleveland, OH, United States)
Gabb, T. P. (NASA Lewis Research Center Cleveland, OH, United States)
Miner, R. V. (NASA Lewis Research Center Cleveland, OH, United States)