Fracture toughness testing and toughening mechanisms of some commercial cobalt-free hardfacing alloys
Hardfacing alloys are weld deposited to provide a wear resistant surface for structural base materials. Commercial low cobalt hardfacing alloys are being evaluated to reduce plant activation levels. Since hardfacing alloys typically must be resistant to cracking to assure adequate in service performance, fracture toughness is a critical material property. Fracture toughness (K{sub IC}) measurements of Fe base, Ni-base, and Co-base hardfacing were performed in accordance with ASTM E399-90 procedure in an effort to identify a tough cobalt-free alternative. Reduced scatter in K{sub IC} data was observed for the Fe base hardfacing, and the 95% lower bound K{sub IC} values were generally higher than the Ni-base Hardfacing alloys. Preliminary crack growth data obtained during precracking indicate that the Ni-base hardfacing possess better fatigue crack growth resistance. However, none of the Fe-base or Ni-base hardfacing have K{sub IC} values that are comparable to the reference Co-base hard facing. The test specimens were machined from thick (0.5 inches) weld deposits, and the microstructures of the test specimens are compared with the more prototypic, thinner deposits. Microstructural and fractographic examinations are used to characterize the fracture mechanisms and delineate the operative toughening mechanisms. Crack deflection and crack bridging toughening mechanisms are shown to be relevant for most of the commercial hardfacing.
- Research Organization:
- Westinghouse Electric Corp., Bettis Atomic Power Lab., West Mifflin, PA (US)
- Sponsoring Organization:
- USDOE Assistant Secretary for Management and Administration, Washington, DC (US)
- DOE Contract Number:
- AC11-93PN38195
- OSTI ID:
- 654147
- Report Number(s):
- WAPD-T--3177; CONF-980429--; ON: DE98004680
- Country of Publication:
- United States
- Language:
- English
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