Aging and Phase Stability of Alloy 22 Welds FY05 SUMMARY REPORT

Aging and Phase Stability Studies of Alloy 22 FY08 Final Report

“…The specimen aged at 750°C for 100 hours shows significant precipitation of small TCP phase particles in both the primary and secondary interdendritic regions. These features can be clearly seen in Comparison of the results obtained for the 1.25" thick welds with those previously obtained for 0.5" welds aged at Haynes, International is shown graphically in Figure 4.5.2.3 [33]. The results for the aged 1.25" thick welds are superimposed on those obtained for the Haynes 0.5" welds aged at 649°C, 704°C, and 760°C for similar times.…”

“…This is reflected in the volume fractions shown in Table 5.4.1.1 [33]. However, after aging at 700°C for 500 hours, the TCP phase volume fraction grew substantially.…”

“…Optical microscopy examination indicates less localized corrosion degradation with increasing annealing temperatures in both the 1 M NaCl and 6 m NaCl + 0.9 m KNO 3 environments [33]. However, the residual surface oxide from the annealing process may have obscured the quantification of the localized corrosion susceptibility from the cyclic potentiodynamic polarization curves.…”

“…Based on previous critical potential tests, the lower nitrate and intermediate temperature NaCl-KNO 3 environments are most likely to be sensitive to material susceptibility. Results from the corrosion testing are detailed in Torres et al [33] and are summarized in this report.…”

“…This was performed by collecting 880 micrographs (for each specimen) and stitching them together to form a collage [33]. The collage layout consisted of 44 rows and 20 columns, with the first row at the top of the weld (last weld pass), and the last row near the center of the weld (first weld pass).…”