Low cycle fatigue of As-HIP and HIP + forged Rene 95

Journal Article · Mon Oct 01 04:00:00 EDT 1979 · Metall. Trans., A; (United States)

DOI:https://doi.org/10.1007/BF02812013· OSTI ID:5925976

Bashir, S; Taupin, P; Antolovich, S D

The continuous cycling and hold time low cycle fatigue properties of the Ni base superalloy Rene 95 were studied at 649/sup 0/C usng powder products (-60 mesh) in the as-HIP and HIP + forged conditions. It was shown that cracks were initiated by pores, by ceramic particles and by a classical stage I mechanism for both materials and for both cycle characters. For the continuously cycled as-HIP material, deformation was restricted to well defined bands at low strains and became homogeneous as the strain level increased. The total energy to fracture increased abruptly in the low strain regime and this was also reflected by a break in the Coffin-Manson plot. In all cases cracks initiated at pores. The hold time specimens exhibited an extremely high dislocation density and surface connected initiation yet without a significant life reduction. The observations were essentially similar for the HIP + forged material except that deformation tended to be confined to well defined slip bands even at high strains and to some extent even for the hold time tests. This behavior was attributed to the fact that the ..gamma..'-precipitates were smaller, more coherent and more readily sheared by dislocations which were strongly paired. There was a marked tendency for crack propagation to change from transgranular to intergranular (also observed for the as-HIP material) at a unique combination of crack length and plastic strain. The transition occurred at shorter crack lengths for the HIP + forged material except when crack initiation was subsurface. In this case the transition was delayed and the life was greatly enhanced, indicating that the environment plays a major role in determining the fatigue life.

• Research Organization: Univ. of Cincinnati, OH
• OSTI ID: 5925976
• Journal Information: Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 10:10; ISSN MTTAB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
AGING
ALLOYS
ALUMINIUM ALLOYS
CARBON ADDITIONS
CHEMICAL COMPOSITION
CHROMIUM ALLOYS
COBALT ALLOYS
CRACKS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DEFORMATION
DISLOCATIONS
FABRICATION
FAILURES
FATIGUE
FORGING
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HEAT TREATMENTS
HIGH TEMPERATURE
HOT PRESSING
LINE DEFECTS
MATERIALS
MATERIALS WORKING
MECHANICAL PROPERTIES
METALLURGY
MICROSTRUCTURE
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
POWDER METALLURGY
PRESSING
RENE 95
TITANIUM ALLOYS
TUNGSTEN ALLOYS
ZIRCONIUM ADDITIONS
ZIRCONIUM ALLOYS