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ML00138 - Jun.2018

Liquid Metal Embrittlement of a HSLA Steel

Micrography of the casting at the surface, presenting a zinc layer deposited in a hot dip process. The thickness of the layer is about 0.3mm in this position, that is higher than expected for this process. The steel substrate is not revealed because the etch was light and the zinc layer protects the low aloy steel during the etch.

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of the , presenting a zinc layer deposited in a hot dip process. The thickness of the layer is about 0.3mm in this position, that is higher than expected for this process. The substrate is not revealed because the etch was light and the zinc layer protects the low aloy during the etch.
M

Material

High Strength Low Alloy
  • ASTM A 217 grade WC4
Ds

Description

The of this lifting device was galvanized as the final step of fabrication and suffered liquid metal embrittlement (LME), with deep zinc penetrations through the previous grain boundaries, as well as internal that were not detected during inspection. This fabrication problem reduced the material capacity to sustain load, favoring a of the material during testing, although the mechanical properties were fine.

C

Chemistry (% in weight)

Product Analysis

0.21C; 0.44Si; 1.00Mn; 0.015P; 0.011S; 0.71Cr; 0.76Ni; 0.44Mo; 0.06Cu; 0.028V.

Associated Images
Aspect of the fracture surface of the 2" diameter casting. The fracture appeared flat, with secondary cracks, and the position of the fracture during the loading test is located in the region that was in tensile stress during the hot dip galvanized process (the part was sustaining its own weight during the zinc hot dip bath).
800
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Aspect Before AnalysisDf - Brittle Fracture
Micrography of the high strenght steel, heat treated, of the casting device. The microstructure is bainitic martensitic.
109
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Bainitic Martensitic
Micrography of the high strenght steel, heat treated, of the casting device. The microstructure is bainitic martensitic.
92
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Bainitic Martensitic
Micrographic detail of the high strenght steel microstructure, bainitic martensitic.
85
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Bainitic Martensitic
Micrography of the casting at the surface, presenting a zinc layer deposited in a hot dip process. The thickness of the layer is about 0.3mm in this position, that is higher than expected for this process. The steel substrate is not revealed because the etch was light and the zinc layer protects the low aloy steel during the etch.
93
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by SEMDf - Zn Layer
Micrographic detail of the zinc layer at the surface.
88
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Zn Layer
Aspect of the other side of the fracture of the 2" diameter lifting device. It failed in a brittle way during loading test. The zinc coating was partially removed from the casting surface of one side of the failed part, for inspection, looking for casting defects. The results showed that the casting part did not present casting defects.
92
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Aspect Before AnalysisDf - Fracture
Scanning electron fractography in low magnification (originally 15x), showing the flat fracture surface with steps and secondary cracks.
72
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Fractography by SEMDf - Brittle Fracture
Scanning electron fractography (originally 500x), showing zinc deposits at the fracture surface.
72
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Fractography by SEMDf - Zn Layer
Scanning electron fractography (originally 1000x), showing details of the zinc deposits at the fracture surface.
72
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Fractography by SEMDf - Fracture
Macrography of a section transverse to the fracture, at the surface of the casting. It is possible to see the large thickness of the galvanized layer at the surface (left side of the figure). There is a white layer over the fracture surface (top of the figure) and branch cracks starting from the surface, parallel to the fracture (in the bottom left side of the figure).
68
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - NItal Etched MacroDf - Secondary Cracks
Micrography of the section transverse to the fracture (top of the figure). The fracture is intergranular, there are several secondary cracks, and there are deposits of zinc over the fracture. The zinc makes difficult the etch with Nital to reveal the microstructure close to the fracture surface.
67
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Fracture
Micrographic detail of the section transverse to the fracture (top of the figure), suggesting the intergranular morphology (at the previous austenite grain boundaries) and the deposits of zinc over the fracture that create a condition of protection of the base metal during the metallographic etch, and the material is not fully etched.
59
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Zn Layer
Micrographic detail of the zinc at the fracture surface.
57
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Micrography by OMDf - Zn Layer
Macrographic detail of the branch cracks starting from the surface, parallel to the fracture.
64
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - NItal Etched MacroDf - Secondary Cracks
Micrography of the cracking parallel to the fracture, as polished. The fracture is branched, there are several secondary cracks, with a clear intergranular morphology.
65
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - As polished micrographyDf - Cracking
Micrographic detail of the branch cracking parallel to the fracture, as polished, showing that the cracks are filled with zinc.
61
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - As polished micrographyDf - Secondary Cracks
Micrographic detail of the branch cracking parallel to the fracture, as polished, showing that the cracks are filled with zinc.
47
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - As polished micrographyDf - Zn Layer
Micrography of the branch cracking parallel to the fracture. There are several secondary intergranular cracks and the cracks are filled with zinc. The zinc appears dark because of the Nital etch, and the steel is not fully revealed because of the protection by the zinc.
54
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Cracking
Micrographic detail of the secondary intergranular cracks, filled with zinc. The zinc appears dark because of the Nital etch, and the steel is not fully revealed because of the protection by the zinc.
48
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Secondary Cracks
Micrographic detail of the secondary intergranular cracks, filled with zinc. The zinc appears dark because of the Nital etch, and the steel is not fully revealed because of the protection by the zinc.
44
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Zn Layer
Micrography of the branch cracking parallel to the fracture. There are several secondary intergranular cracks and the cracks are filled with zinc. The zinc appears dark because of the Nital etch, and the steel close to the cracking is not fully revealed because of the protection by the zinc.
40
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Cracks
Micrographic detail of the intergranular cracks.
43
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Cracks
Micrographic detail of the intergranular cracks.
41
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Intergranular Cracking
Micrography of the intergranular cracks.
37
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Secondary Cracks
Micrographic detail of the intergranular cracks.
37
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Nital Etched Micrography by OMDf - Secondary Cracks
Scanning electron fractography (originally 500x), showing intergranular aspects in the fracture surface.
43
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Fractography by SEMDf - Intergranular Fracture
Scanning electron fractography (originally 1000x), showing intergranular aspects in the fracture surface.
42
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Fractography by SEMDf - Intergranular Cracking
Scanning electron fractography (originally 2000x), showing intergranular aspects in the fracture surface.
47
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Fractography by SEMDf - Intergranular Fracture
Fractographic image of the final fracture (originally 500x), presenting a ductile micromechanism by dimples. The part was embrittled by the presence of zinc in the grain boundaries and the final fracture occurred by ductile overloading, showing that the material properties were fine out of the embrittled regions.
43
VIEW
ML00138 / Jun.2018
Liquid Metal Embrittlement of a HSLA Steel
M - High Strength Low AlloyP - Coated ProductAp - Mechanical IndustryCd - Liquid Metal Embrittlement
Cm - Fractography by SEMDf - Dimples