Accession Number : ADA060298

Title :   Effect of Purity on Reliability Characteristics of High Strength Steel.

Descriptive Note : Final rept. May 75-Dec 77,


Personal Author(s) : Novak,S R ; Loginow,A W ; Reichhold,H M ; Bassett,J G ; McKelvey,G C

PDF Url : ADA060298

Report Date : Jul 1978

Pagination or Media Count : 107

Abstract : The effect of high purity on the mechanical properties and/or environmental-cracking properties of 4340, 18Ni (250 grade) maraging, and 10Ni-modified (AF1410) steels was investigated at a tensile-strength of about 250,000 psi. Normal- and high-purity laboratory-produced materials was tested for each steel. Only the tensile properties of the 4340 steel were determined, whereas for the 10Ni and 18Ni steels the fracture toughness and sensitivity to environmental cracking were also determined. High purity in the 10Ni and 18Ni steels resulted in significantly higher K(Ic) (Fracture toughness) values and increased resistance to stress-corrosion cracking (SCC) in 3.5 percent NaCl solution as established by longer t(inc) and slower da/dt values; high purity in the 10Ni steel increased K(Iscc) (SCC threshold) by a factor of 2.3, and no effect was found for the 18Ni steel. No significant effects of purity were found in smooth-specimen SCC tests in a marine atmosphere; however, the 10Ni steel was immune to SCC and the 18Ni steel was highly susceptible. In limited-duration (1000 hour) tests in hydrogen gas at 40 psig, the high-purity 10Ni steel exhibited no crack extension at high K(I) levels, whereas the other three steels cracked extensively at low K(I) levels. The results show that high purity can improve resistance to fracture and environmental-cracking susceptibility, but the extent of improvement is dependent on the steel-alloy system.

Descriptors :   *Steel, *Nickel steels, *High strength alloys, *Maraging steels, *Purity, Fracture(Mechanics), Toughness, Stress corrosion, Cracking(Fracturing), Hydrogen embrittlement, Tensile properties

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE