Hydrogen Embrittlement of 15-5 PH Stainless Steels
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Fig. 4---2 pct Au + 50 InPb optical micrograph. 170 ~ Magnification 562 times.
500 h.
phase (Fig. 1) which forms on cooling but is not an equilibrium phase. Figures 3 and 4 illustrate this. A slowly cooled 2 pct Au + 50 InPb alloy (Fig. 3(a)) has three phases: i.e., a Pb-In matrix, a second Pb-In (In-rich) phase running through it; and a blocky Au-In intermetallic. Figure 4 shows that equilibrating for 500 h at 170 ~ eliminated the In-rich Pb-In phase, as expected, from the binary Pb-In equilibrium diagram.
Hydrogen Embrittlement of 15-5 PH Stainless Steels G. T. MURRAY The precipitation hardening (PH) martensitic stainless steels possess attractive mechanical properties, e.g. aged yield strengths generally in the 965 MPa (140 Ksi) to 1379 MPa (200 Ksi) range, good toughness, and good corrosion resistance, the combination of which make them attractive materials for aerospace applications. One of the chief drawbacks for such usage is their susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement (HE). HE has been recently reported in 7-4 PH/,2 17-7 PH, 3 PH 13-8Mo 4 and 15-5 PH 5 stainless steels.* Earlier work *Registered Trademarks--Armco Steel Corporation.
has been reviewed by Stanley? In general, the embrittlement increased with increasing strength level. Because of the limited published data on HE of PH stainless steels, and of the continued interest in these materials G. T. MURRAY is Associate Professor, Metallurgical Engineering Department, California Polytechnic State Univers!ty, San Luis Obispo, CA 93407 and Consultant to Naval Weapons Center, China Lake, CA. Manuscript submitted February 2, 1981. 2138--VOLUME 12A, DECEMBER 1981
Karnowsky and Jost ~
Au added to 50 InPb
Heat
Cool
Cool
5 10 20
502 ~ 465 ~ 418 ~
489 ~ 444 ~ 392 ~
495 ~ 448 ~ 398 ~
Figure 3 is similar to the structure shown by Karnowsky and Jost in their Fig. 17. The liquidus temperatures of Karnowsky and Jost are low because of their practice of determining the temperature during cooling. Table I compares the liquidus temperature on heating and cooling from our study with the results of the previous study. The solidus temperature reported by Karnowsky and Jost is actually the 173 ~ peritectic which was detected because of the nonequilibrium phases formed during cooling. The authors acknowledge the help of Mr. R. Olenginski for preparing the metallographic sections, and Mr. S. Cvikevich and Mr. D. Falcon for the microprobe work.
1. M.W. Karnowsky and F. G. Jost: MetalL Trans. A, 1976, vol. 7A, p. 1149.
for rocket components, a program was commenced at the Naval Weapons Center, China Lake, California to evaluate the susceptibility of these materials to HE and SCC. The present work was undertaken to evaluate a simple and expedient screening method for determining the susceptibility of PH steels to HE, prior to conducting fracture toughness measurements. The percent reduction in area at fracture of cathodically charged tensile specimens was selected as the test method since HE of other steels have been frequentl
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