Accession Number : ADA254037


Title :   Effect of Cyclic Strain/Temperature Exposure on Fatigue Life of Coated Turbine Alloys


Descriptive Note : Final rept. Aug 1983-Mar 1987


Corporate Author : PRATT AND WHITNEY WEST PALM BEACH FL MATERIALS ENGINEERING LAB


Personal Author(s) : Barkalow, R H


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a254037.pdf


Report Date : Dec 1988


Pagination or Media Count : 102


Abstract : This program sought basic information about the behavior of coated superalloys versus strain-temperature history in high-temperature, thermal- mechanical exposure. The test plan was based on the observation that test cycle shape strongly impacts the thermal-mechanical-fatigue (TMF) behavior. We found that increasing T sub max. of the Type 1 cycle from 1900 to 2100 deg F shortened the initiation period for TMF cracking and reduced cycles to specimen failure by about 30 to 50 percent. A more radical change in cycle shape, namely a four- sided shaped cycle, was less mechanically damaging (a factor of two) but more severely oxidizing than Type 1 cycles between the same temperature and strain limits. Cyclic speed experiments showed that crack initiation and cycles-to- failure data were not strongly sensitive to testing speed in the range of 1 to 4 cycles per minute. Lower N sub f values for slow speed tests are believed to reflect crack growth in the substrate rather than coating effects. Shut-down steps and hold times at T sub max. and during cooldown from T sub max. generally decreased N sub f values. Coatings; Coated Turbine Alloys; Coated Superalloys; Fatigue Life; Cyclic Strain; Temperature Exposure.


Descriptors :   *TEMPERATURE , *FATIGUE LIFE , *STRAIN(MECHANICS) , *EXPOSURE(GENERAL) , *CYCLES , *TURBINES , *SUPERALLOYS , *COATINGS , *ALLOYS , TEST AND EVALUATION , LAYERS , OBSERVATION , VALUE , BEHAVIOR , FATIGUE , HISTORY , FAILURE , SUBSTRATES , SHAPE , CRACKS , MECHANICAL PROPERTIES , IMPACT , VELOCITY


Subject Categories : Coatings, Colorants and Finishes
      Properties of Metals and Alloys
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE