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This study aims to develop a flow rule for evaluating the relaxation and redistribution of residual stresses during the post-weld heat treatment (PWHT) of hydroelectric runners made from low-carbon martensitic stainless steel (13Cr-4Ni composition). During the PWHT, austenite reforms in the filler metal and surrounding areas of the base metal near welded joints. The evolving inelastic strain rate with reformed austenite led to defining two distinct flow rules in the pure martensitic (α′) and austenitic (γ) phases. A linear rule of mixture was then applied to assess global effective stress based on the inelastic strain rate and current austenite fraction during the PWHT. A unified constitutive model incorporating drag stress and back stress, evolving with creep and plastic deformation mechanisms during the PWHT, described the stress–strain behavior. To validate this analysis, a third flow rule was determined in the 18% tempered austenitic microstructure, compared with the rule of mixture's effective stress contribution from each phase on the inelastic strain rate. Isothermal constant strain rate tests in stabilized crystalline microstructures evaluated constants specific to their respective flow rules. This study demonstrates the stability of reformed austenite at elevated temperatures during slow cooling and its significant influence on the mechanical properties of 13Cr-4Ni steels. The effectiveness of estimating yield stress using the rule of mixture based on individual phase behaviors is also confirmed. [ABSTRACT FROM AUTHOR]

The austenitic stainless steel E309L filler is a commonly used material for in-situ crack repairs of hydro-turbines due to its high weldability, mechanical and chemical compatibility with the turbine's base material. However, experimental data for the as-welded E309L filler is scarce. In this paper, the mechanical properties of as-deposited 75% Ar/25% CO 2 flux-cored arc welding E309L austenitic stainless steel are investigated. The material is shown to be rate- and temperature-sensitive. Furthermore, although the directional nature of the welding/repair process might suggests otherwise, the response is found to be isotropic. Finally, a classic three-dimension Johnson-Cook plasticity theory is implemented and reproduces the experimental results with good accuracy. [ABSTRACT FROM AUTHOR]