TY  - SER
AU  - Anastasio,S.
AU  - James,J.
AU  - Fitz-Gerald,J.
TI  - Corrosion of superaustenitic stainless steel N08367 brazed with a Nickel-Chromium-Silicon-Phosphorous alloy: Electrochemical corrosion behavior of isolated and combined materials
PY  - 2009///
CY  - 
PB  - 
N2  - Transcripción del resumen del autor. The corrosion of superaustenitic stainless steel (SASS) Al-6XN (Fe-24Ni-20Cr-6.3Mo-0.22N in wt%, UNS N08367) brazed with a commercial brazing alloy (with a composition of Ni-22Cr-6.3Si-3.8P) in 0.6 M sodium chloride (NaCl) solution is reported. The SASS sheet material was intrinsically resistant to pitting and crevice corrosion in NaCl solution at room temperature, as indicated by its performance in both multiple crevice assembly exposures and electrochemical polarization testing. The open-circuit potential of isolated SASS (UNS N08367)fell roughly 900 mV below its critical potential for crevice corrosion repassivation (Ecrev,r). Isolated beads of the Ni-22Cr-6.3Si-3.8P braze alloy exhibited open-circuit potentials near its measured Ecrev,r of -0.200 V vs. saturated calomel electrode (SCE) when prepared at 1,150°Cfor 60 min in a vacuum furnace followed by a furnace cool. This was related to both the low pitting resistance equivalent number (PREN) of the solid solution phase as well as the segregation of beneficial chromium due to the complex microstructure of the solidified braze alloy in a bead form, representative of a brazed joint of infinite clearance. This complex microstructure is a result of the formation of intermetallic compounds involving the melting point depressants (silicon and phosphorus) in the braze alloy. Brazing UNS N08367 SASS with a Ni-22Cr-6.3Si-3.8P braze alloy (1,150°C/60 min) produced an extrinsic mode of crevice corrosion which initiated in the braze surface but propagated into the SASS. Multiple crevice assembly tests in 6 wt% ferric chloride (FeCl3) solution and 0.6 M NaCl at neutral pH revealed that the brazed SASS alloy was heavily attacked while the bare unbrazed UNS N08367 SASS surface exhibited no effects. Such crevice corrosion attack greatly exceeded the thickness of the brazed alloy layer, indicating corrosion penetration into the SASS. This corrosion of the brazed SASS was explained by a dissimilar metal crevice corrosion mechanism and was not attributed to intrinsic sensitization by the braze thermal treatment
ER  -