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- Title
Strength and toughness of sintered plus forged T1 high speed steel.
- Authors
GOMES, M. A.; WRIGHT, C. S.; WRONSKI, A. S.
- Abstract
The stresses for macroscopic plastic flow and critical stages of fracture, fracture toughness and hardness of sintered plus forged T1 high speed steel were determined. The results are compared to similar data for sintered, sintered to closed porosity plus hot isostatically pressed and electroflux refined (EFR) alloys of comparable composition. EFR meltstock, with addition of 0.6 wt% Mo, was water-atomized in a 200 kg unit which incorporated ceramic filters and an argon shroud to ensure maximum cleanliness. The powder was sieved, <125 μm, vacuum annealed, blended, isostatically compacted and vacuum sintered and hot forged to produce a 300 kg billet. Mechanical properties were determined in four-point bending of heat-treated beam specimens. Most samples showed evidence of macroscopic plastic flow, up to ∼1%, beyond a stress of ∼1.8 GPa, σY. Using surface replica microscopy, crack nucleation was detected at stresses σN, between 0.5 and 0.9 σY, and subcritical short crack growth, at stresses generally larger than σY. Fracture, from crack nuclei associated (only) with fractured M6C carbides, took place at stresses, σF, in the range 1.4 to 3.0 GPa Macroscopic fracture toughness, KIC, was in the range 17–24 MPa m1/2 and, like σN and σF, appeared to depend sensitively on the tempering temperature. The most attractive combination of properties, for the overtempered, 580°C, structure at HV50 ∼750 appears to be: σY≈1.9 GPa, σF≈2.8 GPa, KIC≈23 MPa m1/2. These values are comparable to those for EFR aerospace quality T1 high speed steel.
- Subjects
SINTERING; HEAT treatment of steel; TEMPERING; STRENGTH of materials; STRAINS &; stresses (Mechanics)
- Publication
Journal of Materials Science, 1997, Vol 32, Issue 7, p1799
- ISSN
0022-2461
- Publication type
Article
- DOI
10.1023/A:1018592404209