The effect of heat treatment on the microstructure and mechanical properties of Ni-base superalloy Haynes 282 was investigated. Applying a standard two-step ageing (1010 °C/2 h +788 °C/8 h) to the as-received, mill annealed, material resulted in a the presence of discrete grain boundary carbides and finely dispersed intragranular γ′, with an average size of 43 nm. This condition showed excellent room temperature strength and ductility. The introduction of an additional solution treatment at 1120 °C resulted in grain growth, interconnected grain boundary carbides and coarse (100 nm) intragranular γ′. The coarser γ′ led to a significant reduction in the strength level, and the interconnected carbides resulted in quasi-brittle fracture with a 50% reduction in ductility. Reducing the temperature of the stabilization step to 996 °C during ageing of the mill annealed material produced a bi-modal γ′ distribution, and grain boundaries decorated by discrete carbides accompanied by γ′. This condition showed very similar strength and ductility levels as the standard ageing of mill-annealed material. This is promising since both grain boundary γ′ and a bi-modal intragranular γ′ distribution can be used to tailor the mechanical properties to suit specific applications. The yield strength of all three conditions could be accurately predicted by a unified precipitation strengthening model.

http://publications.lib.chalmers.se/records/fulltext/245117/local_245117.pdf

Influence of heat treatment on the microstructure and tensile properties of Ni-base superalloy Haynes 282

The fukushima disaster-systemic failures as the lack of resilience

Electrochemical noise (EN), as one of the most promising in situ electrochemical methods in corrosion and electrochemical science, has been developing rapidly in recent years with the advancements in instrumentation and signal processing methods. One advantage of EN is its application in long-term or early stage corrosion process monitoring because it instantly detects corrosion rate and corrosion forms. Investigators have applied various mathematical methods to extract characteristic parameters from EN. In this paper, identifying corrosion forms using parameters obtained from time domain, frequency domain and time–frequency domain is reviewed, and the correlation between parameters and corrosion forms is discussed. Finally, other in situ techniques are recommended to be employed synchronously with EN measurement in order to obtain reliable analyses.

Detection of corrosion degradation using electrochemical noise (EN): review of signal processing methods for identifying corrosion forms

https://cyberleninka.org/article/n/867021.pdf

On the role of boron on improving ductility in a new polycrystalline superalloy

The history of dynamic straining in stress corrosion cracking studies and the evolution of the slow strain rate test (SSRT) are reviewed. Smooth and notched specimens; the importance of strain rate, electrode potential, and other environmental factors; the evaluation of test results; and comparisons to other techniques are addressed. The SSRT’s application in research for oil and gas sour service, buried natural gas pipelines, ethanol transportation, nuclear power, low pressure turbines, and mechanism studies is summarized and its usage by material, industry, and geographic region quantified. Standard test procedures are compared and improvements suggested. The more recent use of cyclic loading is discussed and areas for future study proposed.

Sung-Woo Kim

Papers

M23C6 precipitation behavior and grain boundary serration in Ni-based Alloy 690

Intergranular oxidation of Ni-based Alloy 600 in a simulated PWR primary water environment

ROLE OF GRAIN BOUNDARY CARBIDES IN CRACKING BEHAVIOR OF Ni BASE ALLOYS

Electrochemical noise analysis of PbSCC of Alloy 600 SG tube in caustic environments at high temperature

Primary water stress corrosion cracking behavior of an Alloy 600/182 weld