Hydrogen embrittlement of nodular cast iron

Abstract

Ferritic nodular cast iron, intended for use as the material for inserts of canisters for long‐term geological disposal of spent nuclear fuel, was studied for hydrogen sensitivity. In the canisters, the insert provides the mechanical strength against external loads. Hydrogen was charged from 0.1 N H2SO4 solution in free‐corrosion tests and under controlled cathodic potential. Hydrogen uptake and trapping were then measured using thermal desorption spectroscopy. The hydrogen desorption rate after hydrogen charging manifests two distinct peaks. Plastic deformation during hydrogen charging increases the hydrogen uptake considerably. Hydrogen reduces the elongation to fracture and time to fracture in slow strain rate testing and constant load testing (CLT), respectively. Especially, the strain rate in CLT is dramatically increased. The appearance of hydrogen‐induced cracking in the ferrite phase changes from ductile dimple fracture to brittle cleavage fracture due to hydrogen charging, which initiates from the interphases of the graphite nodules. The results are discussed in terms of the role of hydrogen and the graphite nodules in hydrogen embrittlement of ductile cast iron.

DIC Analyses and Parameter Calibration of a Strain Aging Sensitive Ductile Cast Iron

“…Moreover, especially for the use of this material in a longterm geological repository, it would be interesting to expand the experimental data set with measurements at even lower strain rates and at different temperatures. Lastly it would be of interest to assess the interaction between DSA and hydrogen embrittlement [28], since the easy diffusion of the small hydrogen atoms may be expected to affect the interaction of other interstitial atoms with dislocations, and therefore affect both the energetics and the kinetics of the formation of Cotterell clouds believed to be responsible for dynamic strain aging.…”

An improved simulation modelling on the heat transfer process of wire-feeding spheroidization in iron melt

“…In the production process, the treatment of wire-feeding spheroidization may directly affect the internal quality and mechanical properties of materials [4,5]. The common treatment methods in industrial production include the flushing method, tundish-cover, plunging magnesium under pressure, rotary ladle processes, wire-feeding method and so on [6][7][8]. Among them, the most traditional approach is the flushing method, which is simple and operates easily, but it has some shortcomings, such as a low absorption rate of magnesium, large environmental pollution and a low degree of automation.…”

Laser Welding of Grey Cast Iron with Spheroidal Graphite-Influence of Process Parameters on Crack Formation and Hardness

“…The impact of these microstructures is seen in the reduction of tensile strength and loss of ductility. Furthermore, the welded joint is susceptible to cracking in the weld metal (WM) and heat affected zone (HAZ), not only due to brittle phases but also as a result of hydrogen embrittlement, as it was recently published for bulk EN-GJS-400-15 by Forsström et al [3] and Sahiluoma et al [4]. Previous research considered different measures to improve weldability in shielded arc metal welding.…”