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Metallurgical Transactions A

, Volume 10, Issue 9, pp 1265–1271 | Cite as

Fracture and fatigue in M-50 and 18-4-1 high speed steels

  • J. A. Rescalvo
  • B. L. Averbach
Mechanical Behavior

Abstract

The plane strain fracture toughness values,K Ic , the fatigue crack growth rates and the tensile properties of M-50 and 18-4-1 high speed steels have been measured as a function of tempering temperature. The M-50 was a vacuum arc remelted grade (VIM-VAR) and the 18-4-1 an electroslag grade, and both are used in mainshaft gas turbine bearings. At the usual hardness for bearings, Rockwell C 62, 18-4-1 exhibited a slightly higher fracture toughness (21 MPa·m1/2) than M-50 (18 MPa·m1/2). The fatigue crack growth rates were very similar, and in the slow growth region followed the usual power law,dC/dN=(ΔK) m withm=3 to 4. The crack propagation rates were still significant at values as low as ΔK=5 MPa·m1/2. SEM studies of the fracture surfaces showed complex transgranular fracture paths for both steels. The tensile strengths and the elongations of M-50 were somewhat higher than the corresponding values for 18-4-1 but the yield strengths of the two steels were similar. The microstructures of these steels were markedly different, with M-50 exhibiting 2.6 vol pct undissolved carbides and the 18-4-1 showing 15.2 vol pct carbides, but the fatigue and fracture behaviors were similar.

Keywords

Fracture Toughness Fatigue Crack Crack Growth Rate Fatigue Crack Growth Fatigue Crack Propagation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© The Metallurgical of Society of AIME 1979

Authors and Affiliations

  • J. A. Rescalvo
    • 1
  • B. L. Averbach
    • 1
  1. 1.Department of Materials Science and EngineeringMassachusetts Institute of TechnologyCambridge

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