Effect of Some Environmental Conditions on Stress Corrosion Behavior of Ni-Cr-Fe Alloys in Pressurized Water

Abstract

Stress corrosion tests have been run in pressurized water at 600 F (316 C) using double U-bends and double bent beam specimens. The tests were conducted in autoclaves for up to 3000 hours. The composition of the gas phase above the water and the pH were controlled. The materials tested were commercial heats of Inconel (1) 600, Inconel 625, lncoloy(1) 800 and stainless steel Types 304, 304L and 347; some Inconel alloy 600 weldments; and some experimental laboratory compositions. Several heat treatments were included. No attack was observed in specimens stressed at 90 percent of room temperature yield strength. No attack was observed when hydrogen constituted the gas phase. No attack was observed when crevices were absent. The combined action of a high stress, a high oxygen concentration and a crevice did promote intergranular attack and cracking in the crevice area in all alloys tested. The severity of the attack increased with the oxygen concentration. Many specimens heated for 2 hours at 1250 F (677 C) showed deeper attack than annealed specimens. Solution heat treatment, low carbon content or the presence of carbide stabilizers did not eliminate the attack. The behavior of weld metal deposits was not significantly different from that of base plate. Variations in composition within the normal range of Alloy 600 were unimportant. Differences in behavior among the several alloys tested were minor compared to those from environmental effects.

Werkstoff‐ und Korrosionsprobleme in wäßrigen Lösungen bei hohen Temperaturen und Drücken

“…1.4301, 1.4550 und Incoloy 800) zeigten bei der Prufung als Doppel-U-Proben in Wasser von 3 16 "C mit Zusatz von Ammoniak (pH = 10) und unterschiedlichen Gehalten an Luft und Sauerstoff bei Versuchsbeginn interkristalline SpannungsrSkorrosion ( 16). Die Risse traten in der Zugzone des inneren U-Bogens auf und waren bei sensibilisierten tiefer als bei nichtsensibilisierten Proben.…”

STRESS CORROSION CRACKING AND GENERAL CORROSION OF IRON, NICKEL, CHROMIUM, AND THEIR ALLOYS IN CAUSTIC SOLUTIONS. Quarterly Report, January 15, 1969--April 15, 1969.

“…The effect of alloying elements has been studied by SNOWDEN, 132 KA.GAN and MIKHAILOVA, 133 TRUMAN and PERRY, 134 AKOLZIN et al, 135 COPSON and ECONOMY, 136 and CORIOU et al 127 '. 128 The highlights of their investigations are: (i) increased nickel offers greater SCC resistance to the alloy; (ii) the beneficial effect of nickel is quite dependent upon chromium level in the alloy as shown by TRUMAN and PERRY, 134 and (iii) the addition of molybdenum reduced the resistance to cracking.…”

“…136 The effect of various heat treatments on the stress corrosion behavior of 316 stainless steels in 16.5-23% sodium hydroxide at 10 atmospheres and l80-190°C for 10-15 hours were studied. The cold-worked and loop-shaped specimens exhibited several microcracks whether or not the specimen was welded.…”

“…The failure times for these alloys were 336 and 428 hours. 136 have studied the stress corrosion behavior of a whole series of austenitic stainless steels, Inconels, and Incoloys in lithium hydroxide solutions (pH 10) at a temperature of 3l6°C. Their results are summarized in Table XXI.…”

Effects of Long-Time Exposure in Alloy 625 at 12OO�F, 1400�F and 1600�F

“…(') Alloy 625 has also demonstrated excellent performance in nuclear power plant operation environments where very reliable long-term performance is required. (2) Its wide use is attributed to its specific combination of fabricability, mechanical properties and corrosion resistance.…”