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ML00079 - Jul.2017

Hydrogen Cracking of a Maritime Chain Link

Macrography of the longitudinal section of the broken link, at the fracture surface. There are several secondary cracks, parallel and perpendicular to the link axis.

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of the of the broken link, at the surface. There are several , parallel and perpendicular to the link axis.
M

Material

High Strength Low Alloy
  • UNS G15220 mod
Ds

Description

The chain was operating, intermittent, during one year in a maritime , and the broken link was positioned very close to an anode protecting the structure. A mechanism was identified for the link, that ruptured in a brittle way. The chain link is manufactured in a high strenght and is susceptible to hydrogen embrittlement in a condition.

C

Chemistry (% in weight)

Link Analysis

0.22C; 0.21Si; 1.22Mn; 0.007P; 0.014S; 0.55Cr; 0.45Ni; 0.26Mo.

Associated Images
Micrography of the longitudinal section of the link, presenting secondary cracks in the longitudinal direction, following segregation bands in the material.
541
VIEW
ML00079 / Jul.2017
Hydrogen Cracking of a Maritime Chain Link
M - High Strength Low AlloyP - Chain LinkAp - OffshoreCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Secondary Cracks
Micrographic detail of the longitudinal section of the link, presenting internal cracks of intergranular morphology, typical of a hydrogen assisted mechanism.
52
VIEW
ML00079 / Jul.2017
Hydrogen Cracking of a Maritime Chain Link
M - High Strength Low AlloyP - Chain LinkAp - OffshoreCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Intergranular Cracking
Fracture appearance of the 1 1/4" diameter link. The fracture is flat and presented no evidences of plastic deformation, suggesting a brittle behavior.
54
VIEW
ML00079 / Jul.2017
Hydrogen Cracking of a Maritime Chain Link
M - High Strength Low AlloyP - Chain LinkAp - OffshoreCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
Micrography of a longitudinal section of the link, presenting a tempered martensitic structure, typical of a quenching and tempering heat treatment and compatible with the link hardness of 43 HRc.
67
VIEW
ML00079 / Jul.2017
Hydrogen Cracking of a Maritime Chain Link
M - High Strength Low AlloyP - Chain LinkAp - OffshoreCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Martensite
Macrography of the longitudinal section of the broken link, at the fracture surface. There are several secondary cracks, parallel and perpendicular to the link axis.
38
VIEW
ML00079 / Jul.2017
Hydrogen Cracking of a Maritime Chain Link
M - High Strength Low AlloyP - Chain LinkAp - OffshoreCd - Hydrogen Embrittlement
Cm - Longitudinal Section AspectDf - Longitudinal Section
Micrography of the longitudinal section of the link, close to the fracture surface (in the top of the figure). There are secondary cracks parallel to the fracture.
33
VIEW
ML00079 / Jul.2017
Hydrogen Cracking of a Maritime Chain Link
M - High Strength Low AlloyP - Chain LinkAp - OffshoreCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Secondary Cracks
Micrographic detail of the longitudinal section of the link, close to the fracture surface, presenting the intergranular morphology of the secondary cracks, parallel to the fracture.
29
VIEW
ML00079 / Jul.2017
Hydrogen Cracking of a Maritime Chain Link
M - High Strength Low AlloyP - Chain LinkAp - OffshoreCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Intergranular Cracking
Micrographic detail of the intergranular secondary cracks, parallel to the fracture, typical of a hydrogen assisted cracking.
29
VIEW
ML00079 / Jul.2017
Hydrogen Cracking of a Maritime Chain Link
M - High Strength Low AlloyP - Chain LinkAp - OffshoreCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Intergranular Cracking
Micrographic detail of the intergranular secondary cracks, parallel to the fracture, typical of a hydrogen assisted cracking. Close to the cracking it is possible to see an elongated inclusion, probably of a sulfide type.
26
VIEW
ML00079 / Jul.2017
Hydrogen Cracking of a Maritime Chain Link
M - High Strength Low AlloyP - Chain LinkAp - OffshoreCd - Hydrogen Embrittlement
Cm - Micrography by SEMDf - Intergranular Cracking