Surface Treatment of Austenitic Ni-Fe-Cr-Based Alloys for Improved Resistance to Intergranular-Corrosion and-Cracking

Author:  DL Limoges; G Palumbo; PK Lin, all of (CA)
Source:  US Patent 6,344,097 B1
Doc ID:  2002077
Year of Publication:  2002
Abstract:  
A surface treatment process for enhancing the intergranular corrosion and intergranular cracking resistance of components fabricated from austenitic Ni-Fe-Cr based alloys comprised of the application of surface cold work to a depth in the range of 0.01 mm to 0.5 mm, for example by high intensity shot peening, followed by recrystallization heat treatment preferably at solutionizing temperatures (>900 C.). The surface cold work and annealing process can be repeated to further optimize the microstructure of the near-surface region. Following the final heat treatment, the process can optionally comprise the application of surface cold work of reduced intensity, yielding a cold worked depth of 0.005 mm to 0.01 mm, in order further enhance resistance to cracking by rendering the near surface in residual compression.