Sarwan K. Mannan

Effects of NiAl-β precipitates on fatigue crack propagation of INCONEL alloy 783 under time-dependent condition with various load ratios

Abstract Hold time fatigue crack growth with various load ratios and sustained loading crack growth tests were conducted on INCONEL ® alloy 783 for different microstructures at 650 °C in air. The results showed that the presence of intergranular NiAl-β precipitates significantly improves the resistance to fatigue crack propagation under time-dependent conditions. Crack growth retardation was observed as the cyclic loading approached the sustained loading status.

Oxide-induced crack closure: an explanation for abnormal time-dependent fatigue crack propagation behavior in INCONEL alloy 783

Abstract INCONEL ® (trademark of Special Metals Corporation) alloy 783 was subjected to the fatigue crack growth under sinusoidal and hold-time waveform conditions at 650 °C in air. Interestingly, alloy 783 did not display full time-dependent fatigue crack propagation (FCP) with increase in the hold time. The oxide-induced crack closure is thought to be responsible for the abnormal time-dependent FCP behavior.

Long Term Thermal Stability of INCONEL Alloy 783

Recently developed INCONEL® alloy 783 (nominal composition of Ni-34Co-26Fe-5.4Al-3Nb-3Cr) is precipitation strengthened by Ni3Al-type Gamma Prime and NiAl-type Beta Phases. Due to its low co-efficient of thermal expansion (CTE), high strength, and good oxidation resistance alloy 783 has been specified for use in aircraft gas turbine components such as rings, casings, shrouds, and seals and has been considered for use in a number of other critical industrial turbine components.In this study, commercially produced alloys 783, 718, and 909 were annealed and aged following recommended heat treatments. The materials were then isothermally exposed at 1100°F (593°C) for times up to 10,000 hours. At 1000 hour intervals, specimens of these alloys were removed from the furnace and subjected to room temperature tensile (RTT) and high temperature tensile (HTT) testing at 1200°F (649°C). The microstructure of as-produced and exposed materials was characterized using optical microscopy, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). Variation in tensile properties with isothermal exposure time was correlated with the microstructure.Copyright