Micromechanisms of thermomechanical fatigue: a comparison with isothermal fatigue

Conference · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6999002

Bill, R C

Thermomechanical Fatigue (TMF) experiments were conducted on Mar-M 200, B-1900, and PWA-1480 (single crystals) over temperature ranges representative of gas turbine airfoil environments. The results were examined from both a phenomenological basis and a micromechanical basis. Depending on constituents present in the superalloy system, certain micromechanisms dominated the crack initiation process and significantly influenced the TMF lives as well as sensitivity of the material to the type TMF cycle imposed. For instance, high temperature cracking around grain boundary carbides in Mar-M 200 resulted in short in-phase TMF lives compared to either out-of-phase or isothermal lives. In single crystal PWA-1480, the type of coating applied was seen to be the controlling factor in determining sensitivity to the type of TMF cycle imposed. Micromechanisms of deformation were observed over the temperature range of interest to the TMF cycles, and provided some insight as to the differences between TMF damage mechanisms and isothermal damage mechanisms. Finally, the applicability of various life prediction models to TMF results was reviewed. Current life prediction models based on isothermal data must be modified before being generally applied to TMF.

• Research Organization: National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
• OSTI ID: 6999002
• Report Number(s): N-86-28164; NASA-TM-87331; E-3075; NAS-1.15:87331; USAAVSCOM-TR-86-C-7; CONF-8606200-2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
BRITTLENESS
CRACK PROPAGATION
CRYSTAL STRUCTURE
DATA
EXPERIMENTAL DATA
FATIGUE
GAS TURBINES
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INFORMATION
MACHINERY
MATERIALS
MECHANICAL PROPERTIES
METALLOGRAPHY
MICROSTRUCTURE
NUMERICAL DATA
SERVICE LIFE
TEMPERATURE EFFECTS
TURBINES
TURBOMACHINERY