Fastener

4 cases · 69 images

Crevice Corrosion in a Subsea System — Aspect Before Analysis

Condition: Hydrogen clear all

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Aspect of the broken stud that was fastening a flanged line in a subsea body (tapped hole) using a nut. The fracture, transverse to the stud axis, occurred exactly at the body to flange interface. Adjacent to the fracture, all thread fillets (positioned inside the flange hole) presented cracks at the bottom of the thread. The stud was operating during seven years and was not corroded, indicating it was protected by the anodes. There are also deposits in the fillets suggesting the cathodic protection was effective even inside the flange hole.
799
VIEW
ML00136 / Jun.2018
Hydrogen Cracks of Subsea Studs
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
Aspect of the broken bolt 1 1/2" nominal diameter, after a short time in service (non residente subsea equipment) under cathodic protection. The bolt broke at the thread fillet, close to the head.
800
VIEW
ML00074 / Jun.2018
Hydrogen Cracking of a 17-4 PH Subsea Bolt
M - Precipitation Hardened Stainless SteelP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
Micrography of a longitudinal section of the bolt, as polished, presenting brittle cracks, transverse to the bolt axis.
1241
VIEW
ML00077 / Jun.2018
Hydrogen Cracking of LAS Subsea Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Micrography by OMDf - Cracks
Multiple intergranular cracks transverse to the bolt axis. Hydrogen assisted cracking due to cathodic protection of a high strenght steel. Micrography in the "as polished" condition.
472
VIEW
ML00073 / Jun.2018
Hydrogen Cracking of a LAS Subsea Fastener
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Micrography by OMDf - Intergranular Cracking

More from these cases

ML00136 — Hydrogen Cracks of Subsea StudsM - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Longitudinal section micrography in a position of the thread, far from the failure. The stud presented a quenching and tempering structure and the thread was machined.
84
VIEW
ML00136 / Jun.2018
Hydrogen Cracks of Subsea Studs
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Machined Thread
Microstructure of the stud in the longitudinal section, presenting segregated bands, not uniformly distributed in the section. The bands are associated to elongated and aligned inclusions, and a refined microstructure, probably due to carbon and alloying elements concentration.
69
VIEW
ML00136 / Jun.2018
Hydrogen Cracks of Subsea Studs
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Banded Structure
Microstructure of the stud in the longitudinal section, out of a region of segregation, where the tempered martensitic microstructure appears more uniform.
72
VIEW
ML00136 / Jun.2018
Hydrogen Cracks of Subsea Studs
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Martensite
Micrographic detail of the segregated bands, not uniformly distributed in the section. The bands are associated to elongated and aligned inclusions, and a refined microstructure, probably due to carbon and alloying elements concentration. The localized microhardness (50g) in the band showed levels about 540HV, and out of the band, in the same localtion, presented an average hardness of 321 HV, indicating that the material is non uniform in the regions where there are bands.
66
VIEW
ML00136 / Jun.2018
Hydrogen Cracks of Subsea Studs
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Banded Structure
Micrographic detail of the martensitic structure of the stud in the longitudinal section, out of a region of segregation, where the microstructure appears more uniform and the microhardness is about 370HV (50g).
62
VIEW
ML00136 / Jun.2018
Hydrogen Cracks of Subsea Studs
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Martensite

+24 more from this case →

ML00074 — Hydrogen Cracking of a 17-4 PH Subsea BoltM - Precipitation Hardened Stainless SteelP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Fracture view presenting two diferente aspects, brittle in the bottom of the figure and in the center (most part of the fracture) and ductile in the top of the figure. Nominal diameter of the bolt 1 1/2".
203
VIEW
ML00074 / Jun.2018
Hydrogen Cracking of a 17-4 PH Subsea Bolt
M - Precipitation Hardened Stainless SteelP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Fracture Surface AspectDf - General View
Macrography of a longitudinal section of the broken bolt, at the fracture position, showing that the fracture is partially flat (left side), where the macroscopically aspect is brittle, and a final ductile fracture (right side). Interesting to note that there is a large longitudinal crack, secondary (transverse to the fracture surface).
143
VIEW
ML00074 / Jun.2018
Hydrogen Cracking of a 17-4 PH Subsea Bolt
M - Precipitation Hardened Stainless SteelP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Kalling Etched MacroDf - Longitudinal Section
Fractographic aspect of the broken fastener, at the surface, showing na intergranular morphology typical of a hydrogen assisted mechanism of a high strenght steel under cathodic protection.
224
VIEW
ML00074 / Jun.2018
Hydrogen Cracking of a 17-4 PH Subsea Bolt
M - Precipitation Hardened Stainless SteelP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Fractography by SEMDf - Intergranular Cracking
Detail of the brittle part of the bolt fracture, presenting a secondary cracking longitudinal to the bolt axis. The region of the bolt at the bottom of the thread (close to the surface) is brighter than the internal part of the bolt suggesting different fracture mechanisms.
111
VIEW
ML00074 / Jun.2018
Hydrogen Cracking of a 17-4 PH Subsea Bolt
M - Precipitation Hardened Stainless SteelP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Fracture Surface AspectDf - Fracture
Microscopic aspect of the fracture, close to the bolt surface where the fracture is macroscopically brittle, presenting a predominantly intergranular fracture micromechanism.
108
VIEW
ML00074 / Jun.2018
Hydrogen Cracking of a 17-4 PH Subsea Bolt
M - Precipitation Hardened Stainless SteelP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Fractography by SEMDf - Brittle Fracture

+8 more from this case →

ML00077 — Hydrogen Cracking of LAS Subsea BoltsM - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Aspect of the bolt fracture. The fracture appearance is irregular and there are several secondary cracks from thread fillets.
245
VIEW
ML00077 / Jun.2018
Hydrogen Cracking of LAS Subsea Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
Aspect of the bolt surface with a detail of a secondary crack at the first thread fillet, close to the bolt head.
147
VIEW
ML00077 / Jun.2018
Hydrogen Cracking of LAS Subsea Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - Secondary Cracks
Aspect of the bolt fracture. The fracture appearance is irregular.
137
VIEW
ML00077 / Jun.2018
Hydrogen Cracking of LAS Subsea Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - Fracture
The longitudinal macrosection shows the fracture appearance, irregular, and a lot of secondary cracks transverse to the bolt axis, and longitudinal.
126
VIEW
ML00077 / Jun.2018
Hydrogen Cracking of LAS Subsea Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Longitudinal Section AspectDf - Longitudinal Section
Several secondary cracks in the broken bolt, responsible for the irregular shape of the fracture, that presentes brittle cracks in the transverse and longitudinal directions.
109
VIEW
ML00077 / Jun.2018
Hydrogen Cracking of LAS Subsea Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Longitudinal Section AspectDf - Longitudinal Section

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ML00073 — Hydrogen Cracking of a LAS Subsea FastenerM - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Aspect of the fastener fracture, flat, at a thread fillet.
69
VIEW
ML00073 / Jun.2018
Hydrogen Cracking of a LAS Subsea Fastener
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
One side of the broken socket head screw, presenting secondary cracks in thread fillets adjacent to the position where the nut was tightened.
64
VIEW
ML00073 / Jun.2018
Hydrogen Cracking of a LAS Subsea Fastener
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
Tempered martensitic structure of a longitudinal section of the fastener. Slightly banded material. Hardness level about 42 HRc.
59
VIEW
ML00073 / Jun.2018
Hydrogen Cracking of a LAS Subsea Fastener
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Martensite
Micrography of a longitudinal section of the fastener, at the threat fillet, showing a transverse cracking.
68
VIEW
ML00073 / Jun.2018
Hydrogen Cracking of a LAS Subsea Fastener
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Cracking
Micrography of the secondary crack, in the fillet adjacent to the nut position, where it was opened to the surface.
65
VIEW
ML00073 / Jun.2018
Hydrogen Cracking of a LAS Subsea Fastener
M - Low Alloy Medium Carbon QTP - FastenerAp - SubseaCd - Hydrogen Embrittlement
Cm - Nital Etched Micrography by OMDf - Cracking

+3 more from this case →