Thermomechanical and isothermal fatigue behavior of bare and coated superalloys

Journal Article · Mon Jan 01 04:00:00 EST 1996 · Journal of Engineering Materials and Technology

DOI:https://doi.org/10.1115/1.2805939· OSTI ID:203575

Kadioglu, Y; Sehitoglu, H ^[1]

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1. Univ. of Illinois, Urbana, IL (United States). Dept. of Mechanical Engineering

Thermomechanical fatigue (TMF) and isothermal fatigue (IF) experiments were performed on bare Mar-M246 as well as bare and coated Mar-M247 nickel based superalloys at strain ranges from 0.335 to 1 percent. The experiments were conducted in air, through a temperature range of 500 to 1,038 C at a constant strain rate of 5.0 {times} 10{sup {minus}5} s{sup {minus}1}. Due to the coarse-grained structure of Mar-M246, TMF lives scattered considerably under low strain range conditions. Electron microscopy studies show that significant surface oxidation and gamma prime, {gamma}{prime}, depleted zones occur for Mar-M246 under these conditions. In the surface grain, where the change in {gamma}{prime} morphology is most pronounced, {gamma}{prime} rafted along axes {approx}{+-}45 deg from the loading axis. The influence of a protective coating on the IF and TMF lives of Mar-M247 was also examined. Results indicate that the coating does not significantly affect the fatigue lives of Mar-M247. The oxidation behavior of bare and coating Mar-M247 was investigated via X-ray microprobe and Auger Spectroscopy. Through these analyses, it is evident that the coating was completely degraded when exposed to the test environment for a long time. In both Mar-M246 and Mar-M247, in-phase thermomechanical fatigue (TMF IP) loading resulted in intergranular cracking. TMF IP loading promoted multiple cracks at the coating/substrate interface of coating Mar-M247. Finally, Eshelby techniques were used to calculate stress distributions in the vicinity of a surface oxide and second-phase particle at the coating/substrate interface.

• Sponsoring Organization: USDOE
• OSTI ID: 203575
• Journal Information: Journal of Engineering Materials and Technology, Journal Name: Journal of Engineering Materials and Technology Journal Issue: 1 Vol. 118; ISSN 0094-4289; ISSN JEMTA8
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
AUGER ELECTRON SPECTROSCOPY
CARBON ADDITIONS
CHEMICAL COMPOSITION
CHROMIUM ALLOYS
COBALT ALLOYS
CRACKS
EXPERIMENTAL DATA
FATIGUE
GAS TURBINE ENGINES
HAFNIUM ALLOYS
IRON ADDITIONS
MANGANESE ADDITIONS
MATERIALS
MICROSTRUCTURE
MOLYBDENUM ALLOYS
NICKEL BASE ALLOYS
OPTICAL MICROSCOPY
OXIDATION
S-N DIAGRAM
SCANNING ELECTRON MICROSCOPY
SILICON ADDITIONS
TANTALUM ALLOYS
TITANIUM ALLOYS
TRANSMISSION ELECTRON MICROSCOPY
TUNGSTEN ALLOYS