Evolución microestructural in-situ a alta temperatura de depósitos de soldadura de aceros 9Cr con diferentes contenidos de boro

Resumo

New alloys have been developed for enhancing the performance of the equipment used in thermoelectric power
generation industry. With the objective of increasing the creep resistance of these materials, changes in
the content of some microalloying elements were carried out. Boron bearing in creep strength enhanced 9Cr
steel (CSE9Cr) welds improved martensite stabilization through precipitates. Mechanical properties are
achieved after post weld heat treatments (PWHT). In this work, microstructural evolution of samples subjected
to hot tensile test (HTT) was studied by means of in-situ X-Ray Diffraction (XRD) to determine the effect
of boron in CSE9Cr welds on their mechanical properties at elevated temperatures. All weld metal coupons
were welded using two experimental flux-cored wires with two levels of boron (20 and 60 ppm). A single
post weld heat treatment was applied to each composition. HTT at different temperatures and initial strain
rate were performed while the microstructure evolution was monitoring by in-situ XRD. Mechanical properties
and XRD microstructural parameters were correlated. HTT results were extrapolated using correlation
theory HTT-Creep and Larson-Miller parameterization. It was found that the higher boron in the weld metal
decreased the rate of strength loss at elevated temperatures.
Keywords: creep strength enhanced 9Cr steel, FCAW, in-situ XRD, high temperature mechanical properties.