Tratamiento térmico alternativo para el metal de soldadura de un ACERO 9Cr

Abstract

The creep strength enhanced 9Cr steels (CSE9Cr) are extremely important in the thermoelectric generation industry. The weldability of these alloys is critical as they are used in welded constructed equipments. A microstructure containing a high dislocation density and fine precipitates that reinforce the martensitic matrix is required to improve their creep strength. Mechanical properties are achieved after post weld heat treatments (PWHT), then the optimization of this PWHT is important. An alternative PWHT on deposits of CSE9Cr was studied. All weld metal coupons (AWM) were welded with experimental flux-cored tubular wires. The PWHT´s analyzed were: 1) conventional tempering (760°C x 2h), 2) alternative: solubilizing (1100 °C x 1h) + first tempering (660 °C x 3h) + second tempering (660 °C x 3h). The obtained microstructures were analyzed by SEM and EBSD. Hot tensile tests (HTT´s) at different initial strain rates and temperatures were performed on PHWT samples. HTT´s results were extrapolated using the correlation theory HTT-Creep and Larson-Miller parameterization. The results show that mechanical properties were improved due to the alternative PWHT. Possibly a microstructure with a higher density of dislocations and fine precipitates managed to retain the movement of dislocations for longer times.