TY - JOUR
T1 - The Role of the Slope Out Region on Fatigue Crack Initiation in Electron Beam Welded Waspaloy
AU - Abdul Jawaad, Abdul Kareem MS
AU - Strangwood, Martin
AU - Davis, Claire
PY - 2003/8/1
Y1 - 2003/8/1
N2 - Electron beam (EB) welding can be used to produce compressor drum assemblies for gas turbine aero-engines. The compressor disc components are fatigue limited and. the weld has been identified as a fatigue susceptible region. Electron beam welds in forged and double-heat-treated WASPALOY have been characterized in terms of microstructure, hardness, and fatigue initiation for the base metal, full penetration, and partial penetration (slope-out) weld metal. It has been found that the grain size increases from the base metal through the full penetration weld to the partial penetration weld metal, being largest at the end of full penetration (EOP). Fatigue initiation was found to occur preferentially at the EOP and was associated with the presence of large sulfides at, or close to, the weld surface. The sulfides arise from free surface segregation of sulfur, from the fused metal and surface contamination (arising from a preweld sulfuric acid etching stage), into the slope-out region during weld power down. The sulfides provide fatigue initiation sites and also modify the local composition, changing the type and number density of grain-boundary carbides and gamma' precipitates, in the slope-out region near EOP, resulting in lower hardness regions. Removal of the sulfuric acid etching stage resulted in a more uniform microstructure.
AB - Electron beam (EB) welding can be used to produce compressor drum assemblies for gas turbine aero-engines. The compressor disc components are fatigue limited and. the weld has been identified as a fatigue susceptible region. Electron beam welds in forged and double-heat-treated WASPALOY have been characterized in terms of microstructure, hardness, and fatigue initiation for the base metal, full penetration, and partial penetration (slope-out) weld metal. It has been found that the grain size increases from the base metal through the full penetration weld to the partial penetration weld metal, being largest at the end of full penetration (EOP). Fatigue initiation was found to occur preferentially at the EOP and was associated with the presence of large sulfides at, or close to, the weld surface. The sulfides arise from free surface segregation of sulfur, from the fused metal and surface contamination (arising from a preweld sulfuric acid etching stage), into the slope-out region during weld power down. The sulfides provide fatigue initiation sites and also modify the local composition, changing the type and number density of grain-boundary carbides and gamma' precipitates, in the slope-out region near EOP, resulting in lower hardness regions. Removal of the sulfuric acid etching stage resulted in a more uniform microstructure.
UR - http://www.scopus.com/inward/record.url?scp=0043236127&partnerID=8YFLogxK
U2 - 10.1007/s11661-003-0309-4
DO - 10.1007/s11661-003-0309-4
M3 - Article
SN - 1543-1940
VL - 34A
SP - 1637
EP - 1645
JO - Metallurgical and Materials Transactions A
JF - Metallurgical and Materials Transactions A
IS - 8
ER -