Mechanical Properties, Microstructure and Corrosion Performance of C-22 Alloy Aged at 260°C to 800°C

Aging and Phase Stability of Alloy 22 Welds FY05 SUMMARY REPORT

“…Because Mo provides the Ni-Cr-Mo alloys with their resistance to localized corrosion, segregation of the Mo to the TCP phases can cause a depletion of Mo in the matrix and lead to localized corrosion. Below approximately 600°C, Ni 2 (Cr,Mo), which has an ordered Pt 2 Mo-type structure, forms [2,4,[5][6][7]. This long-range ordering has been linked to an increased susceptibility to stress corrosion cracking and hydrogen embrittlement [2].…”

Aging and Phase Stability Studies of Alloy 22 FY08 Final Report

“…At temperatures above approximately 600°C up to at least 760°C, Tetrahedrally ClosePacked or TCP phases [1] (primarily the Mo-rich µ and P phases) form [2][3][4][5][6]16,17,19]. Because Mo provides the Ni-Cr-Mo alloys with resistance to localized corrosion, segregation of the Mo to the TCP phases can cause a depletion of Mo in the matrix and lead to localized corrosion [2,3,16,17].…”

“…Below approximately 600°C, Ni 2 (Cr,Mo) forms [2,3,[4][5][6]. This long-range ordering (LRO) has been linked to an increased susceptibility to stress corrosion cracking and hydrogen embrittlement [2].…”

“…Because Mo provides the Ni-Cr-Mo alloys with resistance to localized corrosion, segregation of the Mo to the TCP phases can cause a depletion of Mo in the matrix and lead to localized corrosion. Below approximately 600°C, Ni 2 (Cr,Mo), which has an ordered structure, forms [2,3,[4][5][6]. This longrange ordering (LRO) has been linked to an increased susceptibility to stress corrosion cracking and hydrogen embrittlement [2].…”

Correlation Between Two Types of Surface Stress Mitigation and the Resistance to Corrosion of Alloy 22

“…Figure 3 shows more pronounced IGA probably promoted by second phase precipitation due to the exposure of the HAZ to intermediate temperatures (600 to 900°C) for the time involved in the welding process. [14][15] Figure 4 shows the HAZ of a LPB corroded coupon. The aspect of Figure 4 is similar to that of Figure 3 showing that LPB treatment did not decrease the corrosion characteristics of an untreated welded plate (ASW).…”