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ML00160 - Apr.2020

High Temperature Degradation of 310SS

Aspect as received, side A, of the part removed from the rectangular tube that was manufactured from plates, and originally presented two welded seams (not included in the sample). Close to the edges of the sample, where probably were the corners of the rectangular tube, the degradation is in a highest level. Three samples were analysed, with different thicknesses (indicated in the figure). Side A is the side that was in contact with the reaction (product side).

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Aspect as received, side A, of the part removed from the rectangular that was manufactured from , and originally presented two welded (not included in the sample). Close to the edges of the sample, where probably were the corners of the rectangular , the degradation is in a highest level. Three samples were analysed, with different thicknesses (indicated in the figure). Side A is the side that was in contact with the reaction (product side).
M

Material

Austenitic Stainless Steel
  • AISI 310
Ds

Description

The welded rectangular operated during 4 months at temperatures between 800°C and 1100°C in the electric furnace that transforms metallic oxides into metallic power, exposed to and nitrogen, in intermittent cycles. The tube has suffered continuous by scalling at the . The precipitation of carbides and reduced the hot resistance, and created grain boundary oxidation and scale close to tube corners, due to heating/cooling cycles.

C

Chemistry (% in weight)

Plate chemistry

0.049C; 0.48Si; 1.54Mn; 0.019P; 0.019S; 24.3Cr; 18.7Ni; 0.63Mo; 0.09Nb; 0.34Cu; 0.05W; 0.06V.

Associated Images
Aspect as received, side A, of the part removed from the rectangular tube that was manufactured from plates, and originally presented two welded seams (not included in the sample). Close to the edges of the sample, where probably were the corners of the rectangular tube, the degradation is in a highest level. Three samples were analysed, with different thicknesses (indicated in the figure). Side A is the side that was in contact with the reaction (product side).
445
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Aspect Before AnalysisDf - General View
Aspect as received, side B, of the same part. Side B is the external side of the rectangular tube, that was in contact with the electric furnace atmosphere. This surface of side B presented less degradation than the internal surface (side A).
88
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Aspect Before AnalysisDf - General View
Transverse section macrography of the plate where the degradation by thinning is worst, close to the original corners of the tube. The thinning is occurrring from the product reaction side (side A to the bottom of the figure). The macrography shows a reduction in the thickness from 2 mm (right side, sample 2) to almost zero (left side, sample 1).
86
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Transverse Section AspectDf - Thinning
Longitudinal section macrography of the plate where the degradation by thinning is reducing the thickness from 6mm to 4mm (sample 3). The thinning is occurrring from the product reaction side (side A to the bottom of the figure).
83
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Longitudinal Section AspectDf - Thinning
SAMPLE 1 AT THE FRACTURE - Micrography in low magnification where the thickness is reduced to zero (fracture). Side A (process side) to the bottom and side B (furnace environment side) to the top.
85
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Low Mag
SAMPLE 1 AT THE FRACTURE - Micrography at the position where the thickness is reduced to zero. Side A to the bottom. The microstructure is austenite with intergranular and transgranular precipitation. The position of the zero thickness presents aspect of an intergranular fracture, and in side A there are several intergranular cracks from the surface.
83
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation
SAMPLE 1 AT THE FRACTURE - Micrographic detail of the intergranular fracture. The austenitic grains of the material are loosing.
80
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Intergranular Fracture
SAMPLE 1 AT 1 mm THICKNESS - Micrography in low magnification in the center of the thickness. The microstructure is austenitic with secondary intergranular and intragranular precipitation.
76
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Low Mag
SAMPLE 1 AT 1 mm THICKNESS - Micrography in the center of the thickness. The microstructure is austenitic with secondary precipitation, intergranular and intragranular.
76
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation
SAMPLE 1 AT 1 mm THICKNESS - Micrographic detail of the austenite with secondary precipitation. This oxalic acid electrolytic etch is revealing the integranular and transgranular (or intragranular) precipitation. In the grain boundaries it is possible to see: 1) a continuous network of carbide precipitation and 2) isolated islands of sigma phase. In the middle of the grains there are rounded and neddles like carbides.
72
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation
SAMPLE 2 AT 2 mm THICKNESS - Micrography in low magnification in the center of the thickness. The microstructure is austenitic with secondary intergranular and intragranular precipitation. No variation in the microstructure of the center of the plate, compared to sample 1.
52
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Low Mag
SAMPLE 2 AT 2 mm THICKNESS - Micrography in the center of the thickness. The microstructure is austenitic with secondary precipitation, intergranular and intragranular. There are no variations in the microstructure comparing to sample 1.
48
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Secondary Precipitation
SAMPLE 2 AT 2 mm THICKNESS - Micrographic detail of the austenite with secondary precipitation. This oxalic acid electrolytic etch is revealing the integranular and transgranular (or intragranular) precipitation. In the grain boundaries it is possible to see: 1) a continuous network of carbide precipitation and 2) isolated islands of sigma phase. In the middle of the grains there are rounded and neddles like carbides. There are no variations in the microstructure comparing to sample 1.
43
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Intergranular Precipitation
SAMPLE 3 AT 4 mm THICKNESS - Micrography in low magnification in the center of the thickness. The microstructure is austenitic with secondary intergranular and intragranular precipitation, but this micrography was obtained in the longitudinal section, presenting the plate alignment and was etched with NaOH, adopted to colour the sigma phase .
40
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - NaOH Electrolytic Etched MicroDf - Low Mag
SAMPLE 3 AT 4 mm THICKNESS - Micrography in the center of the thickness. The microstructure is austenitic with secondary intergranular and intragranular precipitation, but this micrography was obtained in the longitudinal section, presenting the plate alignment and was etched with NaOH, adopted to colour the sigma phase.
45
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - NaOH Electrolytic Etched MicroDf - Austenitic with Secondary Precipitation
SAMPLE 3 AT 4 mm THICKNESS - Micrographic detail of the material in the center of the thickness, longitudinal section. The microstructure is austenitic and the coloured phases are sigma, at austenitic grain boundaries.
44
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - NaOH Electrolytic Etched MicroDf - Sigma
SAMPLE 1 AT 1 mm THICKNESS - Micrography in low magnification in the center of the thickness, as polished. There are no regions of internal damage (like internal voids or cracks), indicating that the mechanism is only related to surface effects.
42
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - As polished micrographyDf - In the Center of the Thickness
SAMPLE 3, CLOSE TO THE SURFACE OF SIDE A - Micrography, as polished, of the oxides at the process side. In this region there is an oxide layer, not continuous but with no localized penetrations.
43
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - As polished micrographyDf - At the Surface
SAMPLE 3, CLOSE TO THE SURFACE OF SIDE B - Micrography, as polished, of the oxides at the electric furnace environment side. In this region the oxide layer is thinner than in the process side.
46
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - As polished micrographyDf - At the Surface
SAMPLE 1, CLOSE TO THE SURFACE OF SIDE A - Micrography, as polished, of the oxides at the process side. In this region the oxide layer is penetrating into the austenitic grain boundaries, creating a crack like effect.
56
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - As polished micrographyDf - At the Surface
SAMPLE 1, AT THE FRACTURE - Micrography, as polished, of the oxides at the fracture (zero thickness). In this region the oxide layer penetrated through thickness, intergranular, and fractured the material.
63
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - As polished micrographyDf - Intergranular Fracture
SAMPLE 1, AT THE FRACTURE - Micrographic detail, as polished, of the oxides that are penetrating in the austenitic grain boundaries. The oxidation created intergranular cracks in regions close to the edge of the rectangular tube, that are more susceptible to suffer cyclic thermal stresses, since the furnace is weekly turned off, during two days.
55
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - As polished micrographyDf - Intergranular Cracking
SAMPLE 1 AT THE FRACTURE - Micrographic detail by scanning electron microscopy, as polished, of the oxides that are penetrating in the grain boundaries. The EDS showed high Molibdenium content in the penetrating oxides. The process uses Mo oxides to make metallic Mo and the high Mo content at the surface could be responsible for reducing the oxidation resistance of the material and intensifying the thinning at the process side (side A).
47
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Micrography by SEMDf - Oxide Layer
SAMPLE 1 AT 1 mm THICKNESS, SIDE A - Micrographic detail of the austenite with secondary precipitation, close to the surface exposed to the process side. This oxalic acid electrolytic etch is revealing the sigma phase at austenite grain boundaries that is probably intensifying the intergranular oxidation, creating cracks and grain detachemnt leading to quick thinning.
40
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation
SAMPLE 1 AT 1 mm THICKNESS, SIDE A - Micrographic detail of the austenite with secondary precipitation, close to the surface exposed to the process side. This NaOH electrolytic etch is colouring the sigma phase at austenite grain boundaries, creating cracks and grain detachemnt leading to quick thinning.
35
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - NaOH Electrolytic Etched MicroDf - Austenitic with Secondary Precipitation
SAMPLE 1 AT 1 mm THICKNESS, SIDE B - Micrographic detail of the austenite with secondary precipitation, close to the surface exposed to the furnace environment. Although the microstructure is similar all througth the thickness, there are no oxide penetrations into the grain boundaries, even close to the fracture, indicating that the environment is less aggressive.
26
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation
SAMPLE 1 AT 1 mm THICKNESS, SIDE B - Micrographic detail of the austenite with secondary precipitation, close to the surface exposed to the furnace environment. This NaOH electrolytic etch is adopted to colour sigma phase and at this position there are no special formation of sigma in the grain boundaries and there are no oxide penetrations, confirming that the environment is important to create the damage and the internal side of the tube is responsible for the quick degradation in high temperature.
25
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - NaOH Electrolytic Etched MicroDf - At the Surface
High Temperature Degradation of 310SS
2
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Aspect Before AnalysisDf - General View