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ML00076 - Jun.2017

Hydrogen Cracking of a 17-7 PH Subsea Spring

Micrographic detail of the strain hardened aged martensitic structure. Small aligned delta ferrite islands can be seen.

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Micrographic detail of the aged martensitic . Small aligned islands can be seen.
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Material

Precipitation Hardened Stainless Steel
  • UNS S17700
Ds

Description

The spring was in operation in a and broke in a brittle way, without any variation in the operational conditions, after less than 6 month in service. The intergranular and transgranular brittle indicate a effect of this high strength exposed to seawater . Intergranular were observed all through the spring surface.

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Chemistry (% in weight)

Small sample analysis

0.09C; 0.25Si; 0.85Mn; 17.2Cr; 7.1Ni; 0.1Mo; 1.30Al.

Associated Images
The spring presents intergranular and transgranular brittle aspects in the fracture surface.
886
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Fractography by SEMDf - Brittle Fracture
The stainless steel spring broke without any evidence of plastic deformation. The round wire 1/8" diameter has ruptured in a brittle way in this 2" long spring of external diameter of 1/2".
73
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
Detailed aspect of the spring close to the fracture position. The wire surface shows a morphology that reveals the material structure.
58
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - Fracture
The longitudinal section of the spring wire shows a strain hardened martensitic structure, aged to high strength (602 HV 0.3kg). Previous austenite grains are elongated.
55
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Kalling Etched Micrography by OMDf - Longitudinal Section
Micrographic detail of the strain hardened aged martensitic structure. Small aligned delta ferrite islands can be seen.
51
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Kalling Etched Micrography by OMDf - Longitudinal Section
The transverse section of the spring wire shows a strain hardened martensitic structure, aged to high strength (602 HV 0.3kg).
48
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Kalling Etched Micrography by OMDf - Transverse Section
Micrographic detail of the strain hardened aged martensitic structure.
48
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Kalling Etched Micrography by OMDf - Transverse Section
The low magnification fractography by SEM shows a brittle fracture of the spring wire, with several secondary cracks.
45
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Fractography by SEMDf - Brittle Fracture
The fractography by SEM presents intergranular (in the previous austenite grain boundaries) and transgranular fracture micromechanisms. Several secondary cracks perpendicular to the fracture surface.
46
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Fractography by SEMDf - Brittle Fracture
Micrography of a longitudinal section of the wire, at the fracture surface (top of the figure) evidencing the intergranular and transgranular aspects of the hydrogen assisted cracking mechanism.
37
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Micrography by OM using A262 Method ADf - Secondary Cracks
Micrographic detail of a longitudinal section of the wire, at the fracture surface (top of the figure) evidencing the intergranular and transgranular aspects of the hydrogen assisted cracking mechanism. The electrolytic oxalic acid etch reveals the delta ferrite phase. Compare with the Kalling etch in the other figure.
31
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Micrography by OM using A262 Method ADf - Fracture
Micrographic detail of a longitudinal section of the wire, at the fracture surface (top of the figure) evidencing the intergranular and transgranular aspects of the hydrogen assisted cracking mechanism. The Kalling etch does not reveal the delta ferrite. Compare with the electrolytic oxalic acid etch in the other figure.
29
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Kalling Etched Micrography by OMDf - Fracture
Micrographic detail of the spring wire surface, far from the fracture, showing several small intergranular cracks.
40
VIEW
ML00076 / Jun.2017
Hydrogen Cracking of a 17-7 PH Subsea Spring
M - Precipitation Hardened Stainless SteelP - WireAp - SubseaCd - Hydrogen Embrittlement
Cm - Kalling Etched Micrography by OMDf - At the Surface