Microstructural and Fractographic Characterization of a Thermally Embrittled Nuclear Grade Steel: Part II - Quenching and Tempering

Abstract

A nuclear reactor pressure vessel steel was submitted to different quenching and tempering heat treatments aimed at simulating neutron irradiation damage. The obtained microstructures were mechanically tested and submitted to metallographic and fractographic survey. The relevant microstructural and fractographic aspects were employed in the interpretation of the mechanical performance of the thermally embrittled microstructures. A well defined correlation was determined between the elastic-plastic fracture toughness parameter J-integral and the Charpy impact energy, which was achieved for some of the Q&T microstructures.

Sulfate‐reducing bacteria‐assisted hydrogen‐induced stress cracking of 2205 duplex stainless steels

“…In the case of sterile samples, the interior region of the fracture presented a more planar surface with a significant decline in microvoids content. Such microstructure is classified as mixed and brittle mode fracture . SRB‐inoculated samples precharged at 1 mA cm −2 demonstrated fractures similar to those obtained at lower current density.…”

“…These features are characteristic of a high toughness material and typical for the fracture surfaces of 2205 DSS tested in air . Microscopic observations of above‐mentioned fractures revealed nucleation, growth, and coalescence of microvoids mechanism, wherein a complex grid of fine voids or void sheets around the big dimples can be observed (Figure a,b). This double type size distribution of microvoids (large, deep and very small microvoids depicted as 1 and 2 in Figure a, respectively) indicates the role of constituent austenite and ferrite phases in the cracking process of 2205 DSS.…”

A comparison of microstructure and mechanical characteristics correlation of the joint specimens for duplex stainless steel UNS S32304 and super-duplex stainless steel UNS S32750: The role of post-weld heat treatment

“…Based on the microstructure analysis and plasticity behavior of materials, dimples can be of deep conical shape or quite shallow and this would affect the consolidation of microvoids by shear along slip bands. [61][62][63] For sample SFP due to the influence of heat treatment the size of dimples increases and at the end of the holes, small voids are visible. The generation of this morphology could be associated with small austenite grain and smooth austenite-ferrite grain boundary.…”