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ML00011 - Oct.2017

Intergranular SCC of Pure Nickel

Crack propagation with intergranular and transgranular aspects.

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propagation with intergranular and transgranular aspects.
M

Material

Unalloyed Nickel
  • UNS N02200
  • ASTM B 366 Ni 200
Ds

Description

The was in operation in a caustic line, at 90°C/100°C, and presented longitudinal after less than 1 year in service. The failure occurred by a mechanism, intergranular, from the internal fitting surface, not associated to any welded region. The elbow was suffering vibration (pulsing loads) and the frequent cleaning with contaminated condensed steam could contribute for the failure.

C

Chemistry (% in weight)

Product Analysis

99.7Ni; 0.01Cu; 0.07C; 0.11Mn.

Associated Images
Transverse section of the fitting that suffered a longitudinal cracking. As polished. The wrought fitting has suffered intergranular stress corrosion cracking from the internal surface, exposed to hot caustic environment.
566
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Micrography by OMDf - Intergranular Cracking
The fitting presented through wall cracks that lead to leaking. The internal aspect of the surface is presented where the cracks were still in the begining.
127
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Aspect Before AnalysisDf - Crack
Microstructure of the fitting in the transverse section, presenting a granular Ni austenitic structure. No evidences of any phase in the grain boundaries.
113
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Kalling Etched Micrography by OMDf - Austenite
Microstructure of the fitting in the transverse section, presenting a granular Ni austenitic structure. No evidences of any phase in the grain boundaries.
110
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Kalling Etched Micrography by OMDf - Austenite
Microstructure of the fitting in the transverse section, presenting a granular Ni austenitic structure. No evidences of any phase in the grain boundaries.
96
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Kalling Etched Micrography by OMDf - Austenite
After opening the crack the fracture surface presented different aspects close to the internal surface and through the wall propagation. Intergranular at the surface, showing intergranular SCC mechanism, and transgranular with striation, showing the contribution of pulsing loads.
101
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Fractography by SEMDf - Through Wall Cracking
After opening the crack the fracture surface presented different aspects close to the surface, initiation mechanism, and through the wall propagation. Detail of the intergranular cracking mechanism close to the internal surface.
98
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Fractography by SEMDf - Intergranular Cracking
After opening the crack the fracture surface presented different aspects close to the internal surface, in the initiation, and through the wall propagation. Detail of the transgranular striation, showing the contribution of pulsing loads.
98
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Fractography by SEMDf - Fatigue Striation
After opening the crack the fracture surface presented different aspects close to the internal surface, in the initiation, and through the wall propagation. Detail of the transgranular striation, showing the contribution of pulsing loads.
82
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Fractography by SEMDf - Fatigue Striation
Transverse section of the fitting that suffered a longitudinal cracking. As polished. The wrought fitting has suffered intergranular stress corrosion cracking from the internal surface, exposed to hot caustic environment.
70
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Micrography by OMDf - Intergranular Cracking
Transverse section of the fitting that suffered a longitudinal cracking. As polished. The wrought fitting has suffered intergranular stress corrosion cracking from the internal surface, exposed to hot caustic environment.
59
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Micrography by OMDf - Corrosion Cracking
Crack propagation with intergranular and transgranular aspects.
55
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Kalling Etched Micrography by OMDf - Corrosion Cracking
Crack propagation with intergranular and transgranular aspects.
45
VIEW
ML00011 / Oct.2017
Intergranular SCC of Pure Nickel
M - Unalloyed NickelP - Wrought FittingAp - Chemical IndustryCd - Stress Corrosion
Cm - Kalling Etched Micrography by OMDf - Corrosion Cracking