Accession Number : AD0778367

Title :   Corrosion Fatigue Behavior of 4340 and D6AC Steels below K1scc.

Descriptive Note : Technical rept.,

Corporate Author : TRW INC CLEVELAND OHIO

Personal Author(s) : Kortovich,C. S.

Report Date : APR 1974

Pagination or Media Count : 47

Abstract : The corrosion fatigue behavior of low alloy martensitic A1S1 4340 and D6AC steels in distilled water below K1scc was studied. The results indicated that crack growth rates for both steels obeyed power law relationships which were not invariant with respect to each other or to results obtained in an inert argon environment. As a result, the environmental contribution to fatigue crack growth diminished as cyclic stress intensity factor range increased. Activation energy for crack growth in 4340 (750F temper) below the threshold stress intensity factor for stress corrosion cracking, K1scc, compared more favorably with the value for hydrogen adsorption onto a clean iron surface than for hydrogen diffusion through a steel lattice. However, the values obtained in this study indicated that the rate controlling factor was probably not associated with such idealistic processes. The crack growth rates for 4340 (750F temper) increased with loading time in tension and the trend of the data indicated a possible maximum at lower frequencies than those included in this investigation. (Author)

Descriptors :   *Steel, *Corrosion, *Fatigue(Mechanics), Crack propagation, Activation energy, Hydrogen, Stress corrosion, Yield strength, Loads(Forces), Tensile strength, Elongation

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE