This paper considers the measurement of residual stresses induced by mechanical loading in a weld
Type 347 stainless steel. The work is based in part on an ongoing Round Robin collaborative effort
by the Versailles Agreement on Materials and Standards, Technical Working Area 31, (VAMAS
TWA 31) working on ‘Crack Growth of Components Containing Residual Stresses’. The specific
objective of the work at Imperial College London and HMI, Berlin is to examine how residual
stresses and prior straining and subsequent relaxation at high temperature contribute to creep crack
initiation and growth for steels relevant to power plant applications. Tensile residual stresses have
been introduced in the weld by pre-compression and neutron diffraction measurements have been
carried out before and after stress relaxation at 650 oC. Significant relaxation of the residual stresses
has been observed, in agreement with earlier work on a stainless steel. Preliminary results suggest
that the strains local to the crack drop by over 60% after 1000 h relaxation at 650 oC for the weld
steel. The results have been compared with finite element studies of elastic-plastic pre-compression
and stress relaxation due to creep.
Effect of Laves Phase on High-Temperature Deformation and Microstructure Evolution in an 18Cr-2Mo-0.5Nb Ferritic Stainless Steel
