Investigation of the Effect of Short Exposure in the Temperature Range of 750–950 °C on the Ductility of Haynes® 282® by Advanced Microstructural Characterization

Abstract

A Gleeble-based test method has been developed to study the change in the ductility signature of Haynes® 282® during isothermal exposure from 5 s to 1800 s. A temperature range of 750 to 950 °C has been used to investigate the effect of age-hardening reactions. Microstructural constituents have been analyzed and quantified using scanning and transmission electron microscopy. Carbides present in the material are identified as primary MC-type TiC carbides, Mo-rich M6C secondary carbides, and Cr-rich M23C6 secondary carbides. Gamma prime (γ′) precipitates are present in all the material conditions with particle sizes ranging from 2.5 nm to 58 nm. Isothermal exposure causes the growth of γ′ and development of a grain boundary carbide network. A ductility minimum is observed at 800–850 °C. The fracture mode is found to be dependent on the stroke rate, where a transition toward intergranular fracture is observed for stroke rates below 0.055 mm/s. Intergranular fracture is characterized by microvoids present on grain facets, while ductility did not change during ongoing age-hardening reactions for intergranularly fractured Haynes® 282®.

Analysis of γ′ Precipitates, Carbides and Nano-Borides in Heat-Treated Ni-Based Superalloy Using SEM, STEM-EDX, and HRSTEM

“…The similarity in crystal structure sometimes makes the M 6 C and M 23 C 6 carbides challenging to distinguish. The M 6 C usually replace M 23 C 6 carbides in alloys containing approximately over 6 wt% Mo plus its atomic equivalent in W (weight per cent Mo plus one half the weight per cent W) [ 9 , 44 , 45 ]. The combined HRSTEM and STEM-EDX analyses show that I-type phase transformation occurred in René 108 during heat-treatment.…”

Welding Metallurgy and Weldability of Superalloys

“…Researchers were invited to submit innovative research papers in the areas of welding metallurgy, weldability, and associated topics of superalloys. In total, six research papers were published in this Special Issue of Metals, entitled "Welding Metallurgy and Weldability of Superalloys", which presents some of the research trends in the field [1][2][3][4][5][6]. All six research papers were related to weld cracking in some aspect, with the strongest focus on hot cracking [1][2][3][4]6], followed by strain age cracking [5].…”

“…In total, six research papers were published in this Special Issue of Metals, entitled "Welding Metallurgy and Weldability of Superalloys", which presents some of the research trends in the field [1][2][3][4][5][6]. All six research papers were related to weld cracking in some aspect, with the strongest focus on hot cracking [1][2][3][4]6], followed by strain age cracking [5]. The major part of the submission in terms of material was associated with Alloy 718, the "work horse" within the group of superalloys in the aero-engine industry [2][3][4].…”

“…In addition, Haynes ® 282 ® , a superalloy that falls into the same class of superalloys (i.e. precipitation hardening Ni-or Ni-Fe based superalloys) as Alloy 718 was covered in two papers that were investigated [5,6]. Varestraint weldability testing [3,4,6] was the major testing method addressed within the field of weldability testing, followed by Gleeble thermomechanical testing [5].…”

“…al. [5] developed a Gleeble-based test method to study the change in the ductility signature of Haynes ® 282 ® during isothermal exposure from 5 s to 1800 s within the temperature range of 750 to 950 • C. Microstructural constituents (i.e. primary and secondary type carbides as well as hardening precipitates (γ ) were identified).…”