Back to Low Carbon Steel
ML00104 - Dec.2017

Thermal Fatigue of a Boiler Tube

The micrography of the longitudinal section of the tube, close to OD, shows the paralel cracks, filled with oxides, perpendicular to the surface.

1

1441
The of the of the , close to OD, shows the paralel , filled with oxides, perpendicular to the surface.
M

Material

Low Carbon Steel
  • ASTM A 178 grade C
Ds

Description

Several water wall of a were leaking after 10 years in operation. The is associated to formed due to cyclically overheated regions in part of the tube. The localized tube overheating, that promoted coalescing in the but did not reduce the hardness level, is very localized under deposit at the . The actuated as an insulator avoidind uniform heat exchanging. The failure is also assisted by .

C

Chemistry (% in weight)

Tube analysis

0.12C; 0.20Si; 0.47Mn; 0.019P; 0.010S; 0.11Cr; 0.01Ni; 0.03Mo.

Associated Images
The micrography of the longitudinal section of the tube, close to OD, shows the paralel cracks, filled with oxides, perpendicular to the surface.
1441
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - As polished micrographyDf - Close to the External Surface
The micrography of the longitudinal section of the tube, close to ID, shows the paralel cracks, filled with oxides, perpendicular to the surface.
229
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - As polished micrographyDf - Close to the Internal Surface
The water wall tube, external diameter 60.3mm and thickness 3.9 mm, shows circunferential cracks in the middle of the section. Several other tubes have failed after 10 years in service.
716
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Aspect Before AnalysisDf - General View
Aspect of the internal surface of the tube after longitudinal cut. This position is out of the damage area and only a small amount of deposits is evident.
216
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Surface AspectDf - Internal Surface
Aspect of the internal surface of the tube after longitudinal cut. This position is at the damage area where a thick deposit is evident.
186
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Surface AspectDf - Internal Surface
Aspect of the external surface of the tube, presenting a large circunferential crack.
171
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Surface AspectDf - External Surface
Aspect of the internal surface of the tube after cleaning, presenting small circunferential cracks.
144
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Surface AspectDf - Internal Surface
The macrography of a longitudinal section of the tube in the damaged area shows the circunferential cracks, from the internal and external sides of the tube. The outer diameter of the tube is in the top of the figure and the inner diameter is in the bottom of the figure. From the outside there are several paralel cracks, as well as from the inner side.
126
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - NItal Etched MacroDf - Cracks
Micrographic details of the longitudinal section of the tube, close to OD, showing paralel cracks, filled with oxides, perpendicular to the surface.
115
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - As polished micrographyDf - Cracks Transverse to the Surface
Micrographic details of the longitudinal section of the tube, close to OD, showing paralel cracks, filled with oxides, perpendicular to the surface.
109
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - As polished micrographyDf - Thermal Fatigue Cracks
Micrographic details of the longitudinal section of the tube, close to ID, showing paralel cracks, filled with oxides, perpendicular to the surface.
103
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - As polished micrographyDf - Cracks Transverse to the Surface
Micrographic details of the longitudinal section of the tube, close to ID, showing paralel cracks, filled with oxides, perpendicular to the surface.
99
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - As polished micrographyDf - Thermal Fatigue Cracks
Micrography of a longitudinal section of the tube, 200 mm far from the cracked region, in the center of the thickness (3.9 mm) showing a granular ferritic-perlitic structure.
139
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrographic detail of a longitudinal section of the tube, 200 mm far from the cracked region, in the center of the thickness (3.9 mm). Feritic perlitic structure.
113
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrography of a longitudinal section of the tube, at the cracked region, in the center of the thickness, showing an evolution of the perlitic structure into carbides.
110
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Coalesced structure
Micrographic detail of a longitudinal section of the tube, at the cracked region, in the center of the thickness. The pearlitic structure was already degratated into globular carbides.
101
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Coalesced structure
Micrography of the longitudinal section of the tube, close to OD, showing no damage in a section about 200mm far from the cracked region.
92
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrography of the longitudinal section of the tube, close to OD, showing the cracks from the surface. The cracks are filled with oxides and slightly opened by corrosion.
84
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Thermal Fatigue Cracks
Micrographic detail of the thermal fatigue cracking, assisted by corrosion, at the OD, in a longitudinal section. The microstructure is ferrite with coalescing carbides.
77
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Coalesced structure
Micrography of the longitudinal section of the tube, close to ID, showing no damage in a section about 200mm far from the cracked region.
69
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrography of the longitudinal section of the tube, close to ID, showing the cracks from the surface. The cracks are filled with oxides and there is still a layer of oxides at the internal surface, detached from the surface (probably during cleaning).
76
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Thermal Fatigue Cracks
Micrographic detail of the thermal fatigue cracking, slightly assisted by corrosion, at the ID, in a longitudinal section. The microstructure is ferrite with carbides.
85
VIEW
ML00104 / Dec.2017
Thermal Fatigue of a Boiler Tube
M - Low Carbon SteelP - Autogenously Welded TubeAp - BoilerCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Coalesced structure