Effect of prolonged isothermal exposure on elevated-temperature, time-dependent fatigue-crack propagation in INCONEL Alloy 783

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 33; no. 11; pp. 3465 - 3478
• Main Authors: LONGZHOU MA, CHANG, Keh-Minn, MANNAN, Sarwan K, PATEL, Shailesh J
• Format: Journal Article
• Language: English
• Published: New York, NY Springer 01.11.2002; Springer Nature B.V
• Subjects: Alloys; Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fatigue, corrosion fatigue, embrittlement, cracking, fracture and failure; Fatigue, embrittlement, and fracture; Materials science; Metallurgy; Metals. Metallurgy; Physics; Temperature; Treatment of materials and its effects on microstructure and properties; Isothermal condition; Scanning electron microscopy; Inconel alloys; Nickel alloys; Cracking; Experimental study; Heat treatments; Crack propagation; Cracks; Property structure relationship; Microstructure; Cobalt alloys; Fatigue cracks; Tensile properties
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-002-0334-8

The effect of isothermal exposure on the elevated-temperature, time-dependent fatigue-crack propagation (FCP) in INCONEL Alloy 783 is investigated. Commercially produced Alloy 783 was annealed and aged following the standard heat-treatment procedure. One set of specimens was then isothermally exposed at 500 deg C for 3000 hours. All specimens were subjected to FCP tests with various hold-time periods and sustained-loading crack-growth tests at 538 deg C and 650 deg C in a laboratory-air environment. Without a hold time, the as-produced and isothermally exposed materials had comparable FCP rates at both test temperatures. With hold times of 100 and 300 seconds, the as-produced and isothermally exposed specimens had comparable FCP rates at 538 deg C. Hold-time testing of the as-produced material at 650 deg C showed abnormal time-dependent FCP and sustained-loading crack-growth retardation. However, hold-time testing of isothermally exposed material at 650 deg C showed the steady sustained-loading crack growth and fully time-dependent FCP typically observed in many superalloys. Comparison with Alloy 718 data from the literature shows that FCP rates of as-produced Alloy 718 and isothermally exposed Alloy 783 are comparable at 650 deg C. A fully time-dependent FCP model based on the damage-zone concept and a thermal-activation equation is proposed to characterize the FCP behaviors.