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ML00174 - Jul.2021donated by: Ericclapton Fernandes

Carburization of a 347 SS Welded Joint

Sample surface. Microstructure of the plate base metal, exposed to high temperature exhausting gases. Refined austenite and some cracks.

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Sample surface. of the , exposed to exhausting gases. Refined and some .
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Material

Austenitic Stainless Steel
  • AISI 347 Nb stabilized
Ds

Description

After twelve years in service, exposed to exhausting gases (basically methane), between 550°C and 628°C, the gas turbine carcass presented multiple (through wall) at welded regions. A small sample was taken from the cracked area to be analyzed in the laboratory. The austenitic coarse grains at the revealed to be the most damaged regions, creating brittle cracks that propagated easily through thickness.

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Chemistry (% in weight)

Small sample

0.12C; 1.04Si; 1.87Mn; 0.025P; 0.019S; 20.7Cr; 10.5Ni; 0.11Mo; 0.14Ti; 0.07Nb; 0.1Cu.

Associated Images
The carcass was manufactured using niobium stabilized plates, grade AISI 347, with circumferential welds, where the through wall cracks were detected.
303
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Field photoDf - General View
The circumferential welds presented several regions where the multiple cracks appeared, mainly revealed by dye check test.
49
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Aspect by NDTDf - Multiple cracks
Aspect of one region where the cracks appeared, after grinding and polishing. Several branched cracks located in welded regions. It is the region where the sample was taken.
37
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Aspect Before AnalysisDf - At the Surface
The small sample removed for analysis. This wedge sample presents three faces: one polished face (that corresponds to the surface), one fractured face and one cut face.
38
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Testpiece aspectDf - Fracture
The small wedge sample is 4 mm deep in the thickness and the circumferential weld are is about 15 mm width where it appears in the internal side of the carcass. The image shows the crack surface (fracture) where the weld aspect is evident.
32
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Aspect Before AnalysisDf - Fracture
The fracture surface in the sample shows columnar grains in the weld and large facets in the heat affected zone (HAZ) close to the internal surface of the carcass (to the top of the image).
32
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Fractography by SEMDf - Brittle Fracture
Detail of the fracture in the heat affected zone, showing a flat fracture where the fracture is close to the surface of the plate, exposed to the high temperature exhausting gases.
24
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Fractography by SEMDf - Brittle Fracture
Sample surface. Microstructure of the plate base metal, exposed to high temperature exhausting gases. Refined austenite and some cracks.
24
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Oxalic Acid Electrolytic EtchDf - Base Metal
Detailed microstructure of the plate base metal, exposed to high temperature exhausting gases. Refined austenite, precipitation of carbides in the grain boumdaries and some cracks.
23
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Oxalic Acid Electrolytic EtchDf - Austenite
Detailed microstructure of the plate base metal, exposed to high temperature exhausting gases. Refined austenite, precipitation of carbides in the grain boumdaries and some cracks.
24
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Oxalic Acid Electrolytic EtchDf - Crack
Sample surface. Microstructure of the weld metal, exposed to high temperature exhausting gases. Austeno-ferritic structure and some cracks.
20
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Oxalic Acid Electrolytic EtchDf - Weld Metal
Detailed microstructure of the weld metal, exposed to high temperature exhausting gases. Austeno-ferritic structure and some cracks.
21
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Oxalic Acid Electrolytic EtchDf - Ferrite and Austenite
Detailed microstructure of the weld metal, exposed to high temperature exhausting gases. Austeno-ferritic structure, strong carbide precipitation integranular and transgranular, and some cracks.
23
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Oxalic Acid Electrolytic EtchDf - Cracks
Sample surface. Microstructure of the heat affected zone (weld metal to the left side and base metal to the right side), exposed to high temperature exhausting gases. Large austenitic grain size and cracks fully opened and filled with oxides.
24
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Oxalic Acid Electrolytic EtchDf - Heat Affected Zone
Microstructure of the heat affected zone (weld metal to the left side), exposed to high temperature exhausting gases. Large austenitic grain size and intergranular cracks fully opened and filled with oxides.
21
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Oxalic Acid Electrolytic EtchDf - Coarse Structure
Detailed microstructure of the heat affected zone, fully carburized and cracked intergranular. Large austenitic grain size.
20
VIEW
ML00174 / Jul.2021
Carburization of a 347 SS Welded Joint
M - Austenitic Stainless SteelP - Fabrication WeldAp - EnergyCd - Carburization
Cm - Oxalic Acid Electrolytic EtchDf - Intergranular Cracking