The influence of pre-compression on the creep deformation and failure behaviour of Type 316H stainless steel

• Published in: Engineering fracture mechanics 2013-09, Vol.110, p.52-67
• Main Authors: Mehmanparast, A., Davies, C.M., Dean, D.W., Nikbin, K.M.
• Format: Article
• Language: English
• Subjects: 316H stainless steel; Austenitic stainless steels; CCG; Crack initiation; Crack propagation; Creep (materials); Creep crack growth; Creep deformation; Creep strength; Fracture mechanics; Mathematical models; NSW creep crack growth model; Polycarbonates; Pre-compression; Pre-strain; Stainless steels
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2013.08.006

•The pre-compression effects on the creep deformation and crack growth of 316H have been examined.•Pre-compression causes an increase in the yield stress and a reduction in creep ductility.•The CCG rate in the PC material is around seven times higher than short term test data on AR material.•The CCI and CCG trends in long term tests on AR material may be estimated by the PC material test data. The influence of pre-compression to 8% plastic strain at room temperature has been examined on the tensile properties, uniaxial creep deformation, creep crack initiation and growth behaviour of Type 316H stainless steel at 550°C. Uniaxial creep and crack growth tests have been performed on the pre-compressed (PC) material and the results compared to existing long term (>15,000h) and short term test data on as-received (AR) (i.e. uncompressed) material. Pre-compression has been found to increase the materials subsequent yield stress in tension. Therefore the extent of non-linearity observed on the load–displacement curves of uniaxial creep rupture and crack growth tests on PC material is limited compared to AR material. In addition pre-compression causes a significant reduction in creep ductility and rupture time, although similar average and minimum creep strain rates are found in PC and AR materials. The creep crack growth (CCG) data on PC and AR materials have been characterised using the steady state creep C* parameter employing appropriate validity criteria and geometry dependent fracture mechanics parameter solutions. The CCG results are compared to the creep crack growth prediction models. Based on the creep properties, creep ductility and metallurgical observations of the fracture behaviour of the AR and PC materials, it has been shown that short term creep crack growth tests on PC material may be used to predict long term creep crack initiation (CCI) and CCG behaviour of AR material at 550°C.