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Crevice Corrosion in a Subsea System — Aspect Before Analysis

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Aspect of the broken spring. The wire is 1 1/2" diameter and the ourter diameter of the spirals is 12 1/2", in a 20" height spring. It was broken in several pieces.
866
VIEW
ML00137 / Mar.2021
Brittle Fracture of a 15-5 PH Valve Spring
M - Precipitation Hardened Stainless SteelP - SpringAp - Oil and GasCd - Brittle Behavior
Cm - Aspect Before AnalysisDf - General View
Aspect of the CuZn platesheet where it is corroded (cooling medium side). The (hot) air cooler uses treated seawater as the cooling medium and the corroded regions are associated to the regions in the heat exchanger of higher temperatures, and the leakage occurred in regions of contact of the platesheet to cooper alloy tubes.
1167
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - Aspect Before AnalysisDf - Corrosion
Multiple thermal fatigue cracks at the welded joint between the smoke tube (vertical, internal diameter 248mm) and the tubesheet (horizontal, plate of 22 mm thickness). This is a view from the combustion chamber. The dye check tests revealed several parallel cracks.
1249
VIEW
ML00119 / Feb.2018
Thermal Fatigue of a Marine Boiler
M - Low Carbon SteelP - Fabrication WeldAp - ShipCd - Thermal Fatigue
Cm - Aspect by NDTDf - Thermal Fatigue Cracks
Micrography of the welded joint, at the root, presenting hot cracks. The imposed high energy in the root due to the ceramic backing support created a condition for cracking.
1100
VIEW
ML00118 / Jan.2018
Non qualified GMAW of Aluminum Plates
M - Aluminum Magnesium ManganeseP - Welded Testpiece for QualificationAp - ShipCd - Non qualified
Cm - Keller Etched Micrography by OMDf - Hot cracking
The hose connector fracture surface presented different fracture micromechanisms associated to the microstructure: inclusion decohesion, small regions of intergranular fractures (probably due to cementite at grain boundaries), and cleavage of the ferritic structure. All these mechanisms are brittle.
560
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Fractography by SEMDf - Brittle Fracture
Bimetallic engine bearing, removed from service at the end of its life.
356
VIEW
ML00083 / Oct.2017
Steel Back of a Bimetallic Engine Bearing
M - Low Carbon SteelP - Cold FormedAp - ShipCd - Removed From Service
Cm - Aspect Before AnalysisDf - General View
Micrography of a longitudinal section of the 1" plate, in the center of the thickness, presenting a refined ferritic perlitic microstructure. Banded.
310
VIEW
ML00063 / Apr.2017
EH36 1" Plate for Structure
M - CMn SteelP - Rolled PlateAp - ShipCd - Typical manufacturing
Cm - Nital Etched Micrography by OMDf - Grain refined structure
The fracture surface is flat, shows the graphite nodules and cleavage of the ferritic microstructure, indicating that the material have exceeded the capacity to acomodate the stress.
944
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Fractography by SEMDf - Cleavage Facets

More from these cases

ML00137 — Brittle Fracture of a 15-5 PH Valve SpringM - Precipitation Hardened Stainless SteelP - SpringAp - Oil and GasCd - Brittle Behavior
Aspect of the fracture of the spring. Close to the surface the fracture presents the aspect of rusted spots.
132
VIEW
ML00137 / Mar.2021
Brittle Fracture of a 15-5 PH Valve Spring
M - Precipitation Hardened Stainless SteelP - SpringAp - Oil and GasCd - Brittle Behavior
Cm - Aspect Before AnalysisDf - Fracture
The spring ruptured in several positions. This is the aspect of one of the fractures of the spring. In the initiation of the fracture (top side of the figure) the fracture presents a different morphology.
101
VIEW
ML00137 / Mar.2021
Brittle Fracture of a 15-5 PH Valve Spring
M - Precipitation Hardened Stainless SteelP - SpringAp - Oil and GasCd - Brittle Behavior
Cm - Aspect Before AnalysisDf - Brittle Fracture
Microstructure of the spring in a transverse section, presenting an aged martensitic structure.
96
VIEW
ML00137 / Mar.2021
Brittle Fracture of a 15-5 PH Valve Spring
M - Precipitation Hardened Stainless SteelP - SpringAp - Oil and GasCd - Brittle Behavior
Cm - Kalling Etched Micrography by OMDf - Martensite
Corroded spots (shallow pits) at the spring surface.
84
VIEW
ML00137 / Mar.2021
Brittle Fracture of a 15-5 PH Valve Spring
M - Precipitation Hardened Stainless SteelP - SpringAp - Oil and GasCd - Brittle Behavior
Cm - Aspect Before AnalysisDf - At the Surface
Corroded spots (shallow pits full of products) at the spring surface.
80
VIEW
ML00137 / Mar.2021
Brittle Fracture of a 15-5 PH Valve Spring
M - Precipitation Hardened Stainless SteelP - SpringAp - Oil and GasCd - Brittle Behavior
Cm - Surface Aspect by SEMDf - Corrosion

+22 more from this case →

ML00125 — Dezincification of a Cooler TubesheetM - BrassP - PlateAp - ShipCd - Preferential Dissolution
Micrography of a transverse section of the platesheet presenting a duplex structure, alpha (light yellow) and beta (orange) phases.
214
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - FeCl3+HCl+Ethanol Etched MicroDf - Alpha and Beta
Aspect of the tubesheet after removal of the cooper alloy tubes and water cleaning. The corrosion is more intense in the regions of tube connection.
176
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - Surface AspectDf - Corrosion
Transverse section of the tubesheet, after removal of the tubes. The seawater sie is to the top of the figure. It is possible to see regions of localized corrosion close to the tube position and a red layer all through the plate surface.
182
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - Transverse Section AspectDf - Corrosion
Macrographic detail of the transverse section of the tubesheet at the cooper alloy tube position, after removal of the 5/8" tube. The red layer at the top of the plate (exposed to the cooling medium - treated seawater) is a region of selective corrosion, dezincification.
169
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - Transverse Section AspectDf - Corrosion
Macrographic detail of the transverse section of the tubesheet at the cooper alloy tube position, after removal of the 5/8" tube. The "layer" at the top of the plate (exposed to the cooling medium - treated seawater) is a region of selective corrosion, dezincification. It is possible to see that in the right side of the figure, where the cooper tube was positioned, the corrosion damage is deeper.
153
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - Transverse Section AspectDf - Dezincification

+13 more from this case →

ML00119 — Thermal Fatigue of a Marine BoilerM - Low Carbon SteelP - Fabrication WeldAp - ShipCd - Thermal Fatigue
Macrography of the plate (thickness 22mm, in horizontal position) to tube (thickness 12.5 mm, in vertical position) welded joint. The half V groove was welded from the top (position inside the combustion chamber) in five weld beads, and with a small fillet welded from the water side (ouside of the tube). Average hardness of the plate is 180HV1 (1kg), of the tube is 150HV1 and of the weld is 190HV1. Maximum hardness of the tube HAZ is 165HV1 and plate HAZ is 195HV1.
219
VIEW
ML00119 / Feb.2018
Thermal Fatigue of a Marine Boiler
M - Low Carbon SteelP - Fabrication WeldAp - ShipCd - Thermal Fatigue
Cm - NItal Etched MacroDf - Welded Joint
Micrography of the plate in a longitudinal section, presenting a typical ferritic pearlitic structure, banded. The plate is 22 mm thick.
182
VIEW
ML00119 / Feb.2018
Thermal Fatigue of a Marine Boiler
M - Low Carbon SteelP - Fabrication WeldAp - ShipCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Banded Structure
Micrography of the plate in a longitudinal section, presenting a typical ferritic pearlitic structure, banded.
165
VIEW
ML00119 / Feb.2018
Thermal Fatigue of a Marine Boiler
M - Low Carbon SteelP - Fabrication WeldAp - ShipCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrographic detail of the ferritic pearlitic structure of the plate in the longitudinal section.
147
VIEW
ML00119 / Feb.2018
Thermal Fatigue of a Marine Boiler
M - Low Carbon SteelP - Fabrication WeldAp - ShipCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrography of the weld metal in the center os the weld. Columnar grains (of the previous austenite) with primary ferrite in the grain boundaries; ferrite with aligned second phases and acicular ferrite, intragranular.
137
VIEW
ML00119 / Feb.2018
Thermal Fatigue of a Marine Boiler
M - Low Carbon SteelP - Fabrication WeldAp - ShipCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Weld Metal

+16 more from this case →

ML00118 — Non qualified GMAW of Aluminum PlatesM - Aluminum Magnesium ManganeseP - Welded Testpiece for QualificationAp - ShipCd - Non qualified
Micrography of the welded joint, at the root, showing hot cracks with intergranular morphology.
146
VIEW
ML00118 / Jan.2018
Non qualified GMAW of Aluminum Plates
M - Aluminum Magnesium ManganeseP - Welded Testpiece for QualificationAp - ShipCd - Non qualified
Cm - Keller Etched Micrography by OMDf - Hot cracking
Micrographic detail of the welded joint, at the root, presenting hot cracks. The presence of these defects were responsible for reducing the material strenght (rupturing in lower strenght than the requirements) and ductility (cracking in bending tests).
116
VIEW
ML00118 / Jan.2018
Non qualified GMAW of Aluminum Plates
M - Aluminum Magnesium ManganeseP - Welded Testpiece for QualificationAp - ShipCd - Non qualified
Cm - Keller Etched Micrography by OMDf - Hot cracking
The welded joint of the flat position is shown from the root side. It is possible to see that the use of the backing generated the possibility for melting the base metal out of the groove, without detection of this condition during welding, responsible for creating defects and avoiding the WPS qualification.
102
VIEW
ML00118 / Jan.2018
Non qualified GMAW of Aluminum Plates
M - Aluminum Magnesium ManganeseP - Welded Testpiece for QualificationAp - ShipCd - Non qualified
Cm - Aspect Before AnalysisDf - General View
The welded joint of the vertical up position is shown from the root side. It is possible to see that the use of the backing generated the possibility for melting the base metal out of the groove, without detection of this condition during welding, responsible for creating defects and avoiding the WPS qualification.
122
VIEW
ML00118 / Jan.2018
Non qualified GMAW of Aluminum Plates
M - Aluminum Magnesium ManganeseP - Welded Testpiece for QualificationAp - ShipCd - Non qualified
Cm - Aspect Before AnalysisDf - General View
Summary of the welding conditions and qualification test results. NON QUALIFIED WPS. The individual parameters for each welding position are presented in the legend of each macrography, that also presents the amount of beads.
117
VIEW
ML00118 / Jan.2018
Non qualified GMAW of Aluminum Plates
M - Aluminum Magnesium ManganeseP - Welded Testpiece for QualificationAp - ShipCd - Non qualified
Cm - WPS summaryDf - Welded Joint

+22 more from this case →

ML00103 — Brittle Fracture of a Free-Cutting ConnectorM - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Aspect of the external side of the connector, with a longitudinally crack of a brittle aspect. It is a 5/8" connector (15.8 mm).
134
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Aspect Before AnalysisDf - General View
Aspect of the internal side of the connector. The fracture, in the longitudinal direction, presents a brittle aspect. The thickness of the connector is about 2 mm.
126
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Aspect Before AnalysisDf - Brittle Fracture
Macroscopic detail of the brittle fracture, in the longitudinal direction.
105
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Aspect Before AnalysisDf - Brittle Fracture
Micrography of the longitudinal section of the fitiing, in a free-cutting steel. The microstructure is predominantly ferritic and there is a large amount of sulfide inclusions, aligned perpendicular to the forming direction.
98
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Longitudinal Section
Micrographic detail of the longitudinal section of the fitiing, in a free-cutting steel. The microstructure is predominantly ferritic, with small perlitic areas and some free cementite at ferritic grain boundaries. There is a large amount of sulfide inclusions, aligned perpendicular to the forming direction.
106
VIEW
ML00103 / Nov.2017
Brittle Fracture of a Free-Cutting Connector
M - Low Carbon SteelP - Machined PartAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Non Metallic Inclusions

+11 more from this case →

ML00083 — Steel Back of a Bimetallic Engine BearingM - Low Carbon SteelP - Cold FormedAp - ShipCd - Removed From Service
Micrography of a transverse section of the engine bearing, close to the internal surface, showing two layers of bearing alloys that presents a total thickness of 600 microns.
29
VIEW
ML00083 / Oct.2017
Steel Back of a Bimetallic Engine Bearing
M - Low Carbon SteelP - Cold FormedAp - ShipCd - Removed From Service
Cm - Nital Etched Micrography by OMDf - Surface Layer
Micrographic detail of a transverse section of the back steel of an engine bearing, presenting a predominantly ferritic structure, strain hardened.
26
VIEW
ML00083 / Oct.2017
Steel Back of a Bimetallic Engine Bearing
M - Low Carbon SteelP - Cold FormedAp - ShipCd - Removed From Service
Cm - Nital Etched Micrography by OMDf - Predominantly Ferritic
Micrography of a transverse section of the back steel of an engine bearing, presenting a predominantly ferritic structure, strain hardened.
24
VIEW
ML00083 / Oct.2017
Steel Back of a Bimetallic Engine Bearing
M - Low Carbon SteelP - Cold FormedAp - ShipCd - Removed From Service
Cm - Nital Etched Micrography by OMDf - Strain Hardened
Micrography of a transverse section of the back steel of an engine bearing, presenting a predominantly ferritic structure, strain hardened.
24
VIEW
ML00083 / Oct.2017
Steel Back of a Bimetallic Engine Bearing
M - Low Carbon SteelP - Cold FormedAp - ShipCd - Removed From Service
Cm - Nital Etched Micrography by OMDf - Strain Hardened
ML00063 — EH36 1" Plate for StructureM - CMn SteelP - Rolled PlateAp - ShipCd - Typical manufacturing
Micrography of a longitudinal section of the 1" plate, in the center of the thickness, presenting a refined ferritic perlitic microstructure. Banded.
12
VIEW
ML00063 / Apr.2017
EH36 1" Plate for Structure
M - CMn SteelP - Rolled PlateAp - ShipCd - Typical manufacturing
Cm - Nital Etched Micrography by OMDf - Banded Pearlite
Micrography of a longitudinal section of the 1" plate, in the center of the thickness, presenting a refined ferritic perlitic microstructure. Banded.
10
VIEW
ML00063 / Apr.2017
EH36 1" Plate for Structure
M - CMn SteelP - Rolled PlateAp - ShipCd - Typical manufacturing
Cm - Nital Etched Micrography by OMDf - Longitudinal Section
ML00040 — Brittle Fracture of a Valve StemM - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Detail of the cleavage micromechanism.
195
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Fractography by SEMDf - Cleavage Facets
The cast iron microstructure is predominatly ferritic with graphite nodules.
169
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Graphite in Nodules
The micrography of the stem at the fracture region shows a flat fracture with transgranular clevage at the ferritic structure.
137
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture
Micrography presenting a detail of the fracture surface opening to the graphite nodules.
139
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture