Microstructural Characterisation of an Automotive Spark Plug using EBSD.pdf
1
H S Ubhi 1 H Jiang 1 M Keeble 2 , and S Fritze 2 , Microstructural Characterisation of an Automotive Spark Plug using EBSD www.oxford-instruments.com Conclusions • Successful mechanical polishing was achieved for all the components and verified by optical metallography. • SEM/EBSD characterisation was similarly successful in accessing the processes and microstructures of the various components, e.g. coating of the terminal, inter-metallic formation at the interface between the copper and nickel in the central cored electrode, local melting as the erosion mechanism at the platinum electrodes. Introduction A pre-requisite for successful metallography is good sample preparation. This study illustrates the methodology for mechanically polishing an automotive spark plug, utilising both bright field and differential interference contrast optical microscopy to assess the surface condition, prior to SEM/EBSD characterisation. Methodology An automotive spark plug that had come out of service was sectioned and polished using the steps given in Table 1. The sample surfaces were examined using optical microscopy and the microstructures of the various components in the spark plug examined using the SEM/EBSD technique. The EBSD apparatus was attached to a FEGSEM and the EBSD data acquired using OI-HKL Nordlys detector combined with CHANNEL5 software. 1 Oxford Instruments plc, Halifax Road, High Wycombe, Bucks, HP12 3SE, UK. 2 Buehler UK, Step No. Surface Abrasive Lubricant Force Time Platen Speed Head Speed Relative Rotation 1 Apex DGD 75-15µm Water 6lbs until plane 250 60 Comp. 2 UltraPol 9µm MetaDi Supreme 6lbs 6 min 200 60 Comp. 3 Trident 3µm MetaDi Paste Metadi Fluid 7lbs 5 min 200 60 Comp. 4 Trident 1µm MetaDi Paste Metadi Fluid 7lbs 5 min 200 60 Comp. 5 ChemoMet 0.05µm Alumina / Colloidal Silica 7lbs 5 min 80 60 Contra 6 ChemoMet 5 parts Colloidal Silica+2parts 30%H 2 O 2 7lbs 6 min 80 60 Contra Table 1. Details of polishing steps Sectioning: Isomet 5000 Mounting: Simplimet 1000 Preparation: EcoMet-AutoMet Microscopy: Nikon MA-200 Al 2 O 3 Insulator - ceramic The fraction of amorphous phase is 6.6%. Mean size of alumina grains is 3.4µm with a maximum of 16.4µm. All Euler orientation map DIC image EBSP SEM BEI Centre Electrode tip Ni Pt PtNi IPF orientation map 20mm Local misorientation map 20mm FSD image 10mm 20mm SEM BEI DIC image IPF orientation map IPF orientation map IPF orientation map SEM BEI IPF orientation map SEM SEI Platinum tip, fine deformed structure, HAZ, local surface melting during service, weld metal – large grains inter-granular cracks. Pole figures Platinum electrode, large grains, local surface melting during service. Pt Phase map Pt Ni Side electrode EBSP 200mm 200mm IPF orientation map IPF orientation map SEM SEI SEM BEI Terminal: Nickel plating with outer oxide film formation Ferrite Ni All Euler orientation map EDS linescan Terminal Ni EBSP NiO EDS linescan Ferrite EBSP NiO EBSP DIC image Phase map Formation of intermetallic Cr 7 C 3 particles in the copper core at the Cu/Ni interface. Nickel Sheath - mean grain size of 10.9µm. Cr 7 C 3 IPF orientation map of Ni EDS Ni EDS Cr Phase map Ni Cu Cr 7 C 3 particles EDS Cu Cored central electrode 500mm EBSP DIC image DIC image Casing/side electrode joint: melting of casing, grain growth in electrode. Ni Steel Pole figures 500mm CSL boundary map Pole figures 500mm Deformation in thread root from thread roll forming process. IPF orientation map of steel 200mm DIC image DIC image DIC image IPF orientation map Local misorientation map IPF orientation map Steel Casing/side electrode joint Ni Centre electrode tip Side electrode Cored central electrode Casing threads Terminal Insulator - ceramic Casing/side electrode joint Spark Technical Poster_AW.indd 1 28/6/10 15:41:49
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Transcript of Microstructural Characterisation of an Automotive Spark Plug using EBSD.pdf
H S Ubhi1 H Jiang1 M Keeble2, and S Fritze2,
Microstructural Characterisation of an Automotive Spark Plug using EBSD
www.oxford-instruments.com
Conclusions• Successful mechanical polishing was achieved for all the
components and verified by optical metallography.
• SEM/EBSD characterisation was similarly successful in accessing the processes and microstructures of the various components, e.g. coating of the terminal, inter-metallic formation at the interface between the copper and nickel in the central cored electrode, local melting as the erosion mechanism at the platinum electrodes.
IntroductionA pre-requisite for successful metallography is good sample preparation. This study illustrates the methodology for mechanically polishing an automotive spark plug, utilising both bright field and differential interference contrast optical microscopy to assess the surface condition, prior to SEM/EBSD characterisation.
MethodologyAn automotive spark plug that had come out of service was sectioned and polished using the steps given in Table 1. The sample surfaces were examined using optical microscopy and the microstructures of the various components in the spark plug examined using the SEM/EBSD technique. The EBSD apparatus was attached to a FEGSEM and the EBSD data acquired using OI-HKL Nordlys detector combined with CHANNEL5 software.
1Oxford Instruments plc, Halifax Road, High Wycombe, Bucks, HP12 3SE, UK. 2Buehler UK,
Step No. Surface Abrasive Lubricant Force Time Platen Speed Head Speed Relative Rotation
1 Apex DGD 75-15µm Water 6lbs until plane 250 60 Comp.
2 UltraPol 9µm MetaDi Supreme 6lbs 6 min 200 60 Comp.
3 Trident 3µm MetaDi Paste Metadi Fluid 7lbs 5 min 200 60 Comp.
4 Trident 1µm MetaDi Paste Metadi Fluid 7lbs 5 min 200 60 Comp.
5 ChemoMet 0.05µm Alumina / Colloidal Silica 7lbs 5 min 80 60 Contra
6 ChemoMet 5 parts Colloidal Silica+2parts 30%H
2O
2
7lbs 6 min 80 60 Contra
Table 1. Details of polishing steps
Sectioning: Isomet 5000 Mounting: Simplimet 1000 Preparation: EcoMet-AutoMet Microscopy: Nikon MA-200
Al2O3
Insulator - ceramic
The fraction of amorphous phase is 6.6%. Mean size of alumina grains is 3.4µm with a maximum of 16.4µm.
All Euler orientation map
DIC image
EBSP
SEM BEI
Centre Electrode tip
Ni
Pt PtNi
IPF orientation map
20mm
Local misorientation map
20mm
FSD image
10mm20mm
SEM BEI DIC image
IPF orientation mapIPF orientation map
IPF orientation map
SEM BEI
IPF orientation map
SEM SEI
Platinum tip, fine deformed structure, HAZ, local surface melting during service, weld metal – large grains inter-granular cracks.
Pole figures
Platinum electrode, large grains, local surface melting during service.
Pt
Phase map
Pt
Ni
Side electrode
EBSP
200mm 200mm
IPF orientation map
IPF orientation map
SEM SEI SEM BEI
Terminal: Nickel plating with outer oxide film formation
Ferrite
NiAll Euler orientation map
EDS linescan
Terminal
Ni
EBSP
NiO
EDS linescanFerrite
EBSP
NiO
EBSP
DIC image
Phase map
Formation of intermetallic Cr
7C
3
particles in the copper core at the Cu/Ni interface. Nickel Sheath - mean grain size of 10.9µm.
Cr7C3
IPF orientation map of Ni
EDS Ni EDS CrPhase map
Ni
Cu
Cr7C3 particles
EDS Cu
Cored central electrode
500m
m
EBSPDIC image DIC image
Casing/side electrode joint: melting of casing, grain growth in electrode.
Ni
Steel
Pole figures
500mm
CSL boundary map
Pole figures
500mm
IPF orientation map of steel
Casing - thread
Deformation in thread root from thread roll forming process.
IPF orientation map of steel
200mm
DIC image
DIC image
DIC image
IPF orientation map
Local misorientation map
IPF orientation map
Steel
Casing/side electrode joint
Ni
Centre electrode tip
Side electrode
Cored central
electrode
Casing threads
Terminal
Insulator - ceramic
Casing/side electrode
joint
Spark Technical Poster_AW.indd 1 28/6/10 15:41:49
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