Carbide Precipitation and SCC Behavior of Inconel Alloy 690

The effects of grain boundary carbide density and strain rate on the stress corrosion cracking behavior of cold rolled Alloy 690

“…It is recognized that semi-continuous grain boundary carbides induced by thermal treatment can enhance the SCC resistance of Alloy 600 in caustic environment [6] and reducing environment [7][8][9][10][11] although the intergranular carbides reportedly increased the susceptibility to SCC in oxidizing environment [12]. For Alloy 690, the beneficial effect of carbides in caustic has also been found in U-bend tests [13] although it was not revealed in C-ring tests due to insufficient stress applied [14]. Alloy 690 is typically processed in the thermally treated condition.…”

Materials Reliability Program Resistance to Primary Water Stress Corrosion Cracking of Alloys 690, 52, and 152 in Pressurized Water Reactors (MRP-111)

“…The carbon solubility curve of Alloy 690 was investigated by Sarver et a1. [16] The Alloy 690 heats used are listed in Table 2 It should be noted that thermo-mechanical processing of both of these materials may cause grain boundaries to move by recrystallization after all the available carbon has precipitated as carbides on the old grain boundaries, thus creating a "ghost" grain boundary carbide network. Coring or non-equilibrium solidification of the original ingot can also manifest itself in the form of carbide banding.…”

Effects of alloy chemistry, cold work, and water chemistry on corrosion fatigue and stress corrosion cracking of nickel alloys and welds.

“…The greater resistance of Alloy 690 to SCC than that of Alloy 600 is attributed to the differences in the C solubility and carbide precipitation kinetics of these alloys. 14,15 The microstructures of Alloys 182 and 82 are similar to that of wrought Alloys 600 and 690. Under certain thermal treatments, Cr-rich carbides can precipitate at both interdendrite and intradendrite grain boundaries.…”

“…The fatigue CGR (da/dN) database on Alloy 600 is composed of results from 465 tests in air [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] at temperatures up to 538°C. The number of tests at various temperatures are as follows: 166 at room temperature, 13 at 35°C, 9 at 130°C, 14 at 289°C, 26 at 316°C, 20 at 320°C, 11 at 380°C, 76 at 427°C, and 130 at 538°C.…”