抄録
Anodic dissolution behavior of solutioned and of aged Ni-Cr-Al alloys has been studied in 3 mol/dm3 NaNO3 and 2 mol/dm3 NaCl solutions at 30°C. The recovery of γ' from the alloys was determined. using electrolytic extraction technique. The dissolution current efficiency of the alloys was measured in a flow cell under controlled current densities ranging from 1 to 100 A/cm2. The results show that no dissolution of the γ' is observed in NaNO3, and the γ' particles drop out of the electrode surface during dissolution of the alloy matrix, whereas they dissolve anodically in NaCl. The metal removal rate of high γ' content alloys is higher in NaNO3 than in NaCl due to the dissolution behavior of γ'. Moreover, higher metal removal rate is obtained for the aged alloys than for the solutioned alloys in NaNO3. The enrichment in chromium in the alloy matrix during precipitation of γ' facilitates the transpassive dissolution of the aged alloys in NaNO3, and thus the current efficiency becomes close to 100% at all current densities, leading to poor dimensional control.
