Accession Number:

ADA456825

Title:

A Study on the Role of Grain-Boundary Engineering in Promoting High-Cycle Fatigue Resistance and Improving Reliability in Metallic Alloys for Propulsion Systems

Descriptive Note:

Final rept.

Corporate Author:

CALIFORNIA UNIV BERKELEY DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s):

Report Date:

2005-04-30

Pagination or Media Count:

33.0

Abstract:

High-cycle fatigue, involving the premature initiation andor rapid propagation of small cracks to failure due to high-frequency vibratory loading, remains the principal cause of failures in military gas-turbine propulsion systems. The objective of this study is to examine whether the resistance to high-cycle fatigue failures can be enhanced by grain-boundary engineering, i.e., through the modification of the spatial distribution and topology of the grain boundaries in the microstructure. While grain-boundary engineering has been used to obtain significant improvements in intergranular corrosion and cracking, creep and cavitation behavior, toughness and plasticity, cold-work embrittlement, and weldability, only very limited, but positive, results exist for fatigue. Accordingly, using a Ni-base yy superalloy, Rene 104 also referred to as ME3, as a typical engine disk material, sequential thermomechanical cyclic strain and annealing processing is used to i modify the proportion of special grain boundaries, and ii interrupt the connectivity of the random boundaries in the grain-boundary network. The processed microstructures are then subjected to high-cycle fatigue testing, first to assess the crack-propagation properties of long and small cracks to examine how the altered grain-boundary population and connectivity can influence growth rates and overall lifetimes.

Subject Categories:

  • Mechanics
  • Jet and Gas Turbine Engines

Distribution Statement:

APPROVED FOR PUBLIC RELEASE