Metallographic Sample Preparation

Kemet Micrologue contains a number of case studies describing various sample preparation methods and the results obtained by applying these methods. It contains the conclusions of an extensive and intense work that has been conducted at the Application Lab.

Select your material for sample preparation process

Disclaimer: Sample preparation techniques are for guidance purposes only. Kemet recommend these should be tested on non-critical samples first and offer free trials to help establish the optimum process using Kemet equipment and consumables.

Material: A-356 Al-Si Cast Alloy

Results: This alloy is a commonly used engineering material. The microstructure consists of aluminium rich primary solid solution region and euectic.

Etching: 10gr. NaOH+100ml H2O

Cutting: General Purpose BC80NBK Aluminium Oxide cut-off wheel. TRENO-NF Aluminium Oxide cut off wheels can also be used.

Mounting: Ecopress 100 Mounting Press with Black Phenolic Hot Mounting Resin

Mechanical Preparation: DIGIPREP 301 Fully automated grinding and polishing system.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Diamond Grinding Disc 220 Grit Water 25 Until Plain 250 Contra
Grinding Diamond Grinding Disc 600 Grit Water 25 2 250 Contra
Fine Grinding. Diamond Grinding Disc 1200 Grit Water 25 3 300 Contra
Pre Polishing. Fine Grinding disc Green 3µ WP Liquid Diamond Blue 15 4 150 Contra
Final Polishing CHEM-HM Polishing Pad COL-K NC None 15 1 150 Contra

Magnification: 125X (Brightfield)

sample preparation for A-356 Al-Si Cast Alloy

Material: AA8011 Aluminium Alloy

Results: The microstructure of wrought aluminium alloy containing low silicon and iron consists of intermetallic phases (dark areas) in aluminium matrix.

Etching: 10gr. NaOH+100ml H2O

Cutting: General purpose BC80NBK Silicon Carbide cut-off wheel. TRENO-NF SiC cut off wheels can also be used.

Mounting: Ecopress 100 Automatic Mounting Press with Acrylic Transparent Powder

Mechanical Preparation: DIGIPREP 251 Fully automated grinding and polishing system.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Diamond Grinding Disc 220 Grit Water 25 Until Plain 250 Contra
Grinding Diamond Grinding Disc 600 Grit Water 25 2 300 Contra
Fine Grinding. Diamond Grinding Disc 1200 Grit Water 25 3 300 Contra
Pre Polishing. Fine Grinding disc Green 3µ WP Liquid Diamond Blue 15 4 150 Contra
Final Polishing CHEM-H Polishing Pad COL-K NC None 15 1 150 Contra

Magnification: 800X (Brightfield)

sample preparation for AA8011 Aluminium Alloy

Material: AISI 316L Austenitic Stainless Steel

Results: Since the material is highly sensitive against surface deformations, low sample force during mechanical preparation is recommended. Annealed twins can be seen in the microstructure.

Etching: 10% oxalic acid

Cutting: General purpose 8A80MBK Aluminium Oxide cut-off wheel. TRENO-M Aluminium Oxide cut off wheels can also be used.

Mounting: Ecopress 100 Mounting Press with Black-Epoxy (600811)

Mechanical Preparation: FORCIPOL 2V Grinding / Polishing Machine + FORCIMAT Automatic Specimen Mover.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Met Disc Paper 180 Grit SiC Water 25 2 min. or until plane 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 400 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 800 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Pre Polishing MRE Polishing Pad 6µ WP Diamond Suspension Blue 20 3 150 Contra
Final Polishing MBL Polishing Pad 1µ WP Diamond Suspension Blue 20 3 150 Contra

Alternative Prcoess

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Diamond Grinding Disc 220 Grit Water 25 2 min. or until plane 300 Contra
Fine Grinding. Diamond Grinding Disc 600 Grit Water 25 2 300 Contra
Fine Grinding. Green Fine Grinding disc 9µ WP Diamond Suspension Water 25 5 300 Contra
Pre Polishing ASFL Polishing Pad 3µ WP Diamond Suspension Blue 20 3 150 Contra
Final Polishing NSH-B Polishing Pad 1µ WP Diamond Suspension Blue 20 3 150 Contra

Magnification: 800X

sample preparation for AISI 316L Austenitic Stainless Steel

Material: AISI 4340 Low alloy steel

Results: This widely used low alloy steel is usually quenched and tempered. Microstructure consists of fine carbide particles in tempered martensitic matrix. Below giben preparation method results is scratch free surface. A bit over etching helps the carbides to be seen.

Etching: 4% Nital

Cutting: General Purpose 8A80KBK Aluminium Oxide cut-off wheel. TRENO-M Aluminium Oxide cut off wheels can also be used.

Mounting: Ecopress 100 Automatic Mounting Press with Black-Epoxy (600811)

Mechanical Preparation: DIGIPREP 301 Fully automated grinding nad polishing system.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Diamond Grinding Disc 320 Grit Water 25 1 250 Contra
Fine Grinding. Diamond Grinding Disc 1200 Grit Water 25 1 300 Contra
Pre Polishing. Fine Grinding disc Green 3µ WP Diamond Suspension Blue 15 4 150 Contra
Final Polishing MBL Polishing Pad 1µ WP Diamond Suspension Blue 15 1 150 Contra

Alternative Process

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Kemet Dia Grinding Disc 76µ Diamond grinding Water 25 Until Plane 250 Comp
Planar Grinding Kemet Dia Grinding Disc 30µ Diamond grinding Water 25 2 250 Comp
Fine Grinding Kemet Dia Grinding Disc 15µ Diamond grinding Water 25 2 300 Comp
Pre Polishing. Kemet Polishing Disc Green 3µ WP Diamond Suspension Blue 15 4 150 Contra
Final Polishing MBL Polishing Pad 1µ WP Diamond Suspension Blue 15 1 150 Contra

Magnification: 800X (Brightfield)

sample preparation for AISI 4340 Low alloy steel

Material: AISI D2 Cold Work Tool Steel

Results: AISI D2 has high hardness value and high wear resistance due to its high content of chromium and carbon. Since there are many primary alloy carbides, a careful sample preparation is required. Long preparation time and overetching should be avoided. Below given procedure prevents edge roundness.

Etching: 10% Picric Acid + 100 ml. Ethanol

Cutting: General purpose 8A80KBK Aluminium Oxide cut-off wheel. TRENO-S Aluminium Oxide cut off wheels can also be used.

Mounting: Ecopress 100 Automatic Mounting Press with Black-Epoxy (600811)

Mechanical Preparation: FORCIPOL 2V Grinding / Polishing Machine + FORCIMAT Automatic Specimen Mover.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Met Disc Paper 180 Grit SiC Water 30 2 min. or until plane 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 400 Grit SiC Water 25 2 250 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 800 Grit SiC Water 25 2 250 Contra
Bramet Disc Paper
Pre Polishing MST Polishing Pad 6µ WP Diamond Suspension Blue 15 3 150 Contra
Final Polishing MSF or MSFL Polishing Pad 1µ WP Diamond Suspension Blue 15 4 150 Contra

Magnification: 180X

sample preparation for AISI D2 Cold Work Tool Steel

Material: AISI M2 High Speed Tool Steel

Results: The microstructure of this high alloy steel consists of alloy carbides in martensitic matrix. Differential interference contrast makes the primary carbides visible.

Etching: 10% Picric Acid + 100ml Ethanol

Cutting: General purpose 8A80KBK Aluminium Oxide cut-off wheel. TRENO-S Aluminium Oxide cut off wheels can also be used.

Mounting: Ecopress 100 Automatic Mounting Press with Black Penolic or Black-Epoxy

Mechanical Preparation: DIGIPREP 250 Fully automated grinding and polishing system.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Diamond Grinding 220 grit Diamond grinding Water 25 until plane 250 Contra
Fine Grinding. Diamond Grinding 600 grit Diamond grinding Water 25 2 300 Contra
Pre Polishing Fine Grinding disc Green 6µ WM Liquid Diamond Blue 30 4 150 Contra
Final Polishing ASFL Polishing Pad 3µ WM Liquid Diamond Blue 15 2 150 Contra

Magnification: 180X

sample preparation for AISI M2 High Speed Tool Steel

Material: AISI 1020 (Carbon Steel)

Results: The microstructure of AISI 1020 Steel (commonly used in metal constructions) consists of pearlite areas distributed in large ferrite areas. Grain boundries can be seen. For such soft materials, it is recommended to apply low force on the samples to prevent ferrite deformation.

Etching: 2% Nital

Cutting: General Purpose 8A80NBK Aluminium Oxide cut-off wheel

Mounting: Ecopress 100 Mounting Press with Black Phenolic Powder

Mechanical Preparation: FORCIPOL 1V Grinding / Polishing Machine + FORCIMAT Automatic Specimen Mover

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Met Disc Paper 180 Grit SiC Water 25 2 min. or until plane 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 400 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 800 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Pre Polishing MRE Polishing Pad 6µ WP Diamond Suspension GW2 20 3 150 Contra
Final Polishing MBL Polishing Pad 1µ WP Diamond Suspension GW2 20 3 150 Contra

Magnification: 80X

sample preparation for AISI 1020 (Carbon Steel)

Material: AISI 1040 (Carbon Steel)

Results: The microstructural analysis of AISI 1040 which is a widely used steel, is quite straight forward. Microstructure consists of evenly distributed pearlitic and ferritic areas. Grain boundries are visible. In case inclusion rating will be made, it is recommended to use higher force on the sample during mechanical perparation.

Etching: 2% Nital

Cutting: General purpose 8A80MBK Aluminium Oxide cut-off wheel. TRENO-M Aluminium Oxide cut off wheels can also be used.

Mounting: Ecopress 100 Mounting Press with Black Phenolic Powder

Mechanical Preparation: FORCIPOL 2V Grinding / Polishing Machine + FORCIMAT Automatic Specimen Mover.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Met Disc Paper 180 Grit SiC Water 25 2 min. or until plane 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 400 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 800 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Pre Polishing MRE Polishing Pad 6µ WP Diamond Suspension GW2 20 3 150 Contra
Final Polishing MBL Polishing Pad 1µ WP Diamond Suspension GW2 20 3 150 Contra

Magnification: 400X (Ferritic - Pearlitic microstructure, polarized light)

sample preparation for AISI 1040 (Carbon Steel)

Material: AISI 4140 Low alloy steel

Results: Typical tempered martensitic microstructure can be seen in AISI 4140 steel which is commonly used in automative parts. If inlcusion rating will be done, higher wheel speeds and lower mechanical preparation times are recommended.

Etching: 4% Nital

Cutting: General purpose 8A80KBK Aluminium Oxide cut-off wheel. TRENO-S Aluminium Oxide cut off wheels can also be used.

Mounting: Ecopress 100 Automatic Mounting Press with Black-Epoxy (600811)

Mechanical Preparation: FORCIPOL 2V + 250mm Platens + FORCIMAT Automatic Specimen Mover.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Met Disc Paper 180 Grit SiC Water 30 2 min. oruntil plane 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 400 Grit SiC Water 25 2 250 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 800 Grit SiC Water 25 2 250 Contra
Bramet Disc Paper
Pre Polishing MRE Polishing Pad 6µ WP Diamond Suspension Blue 20 3 150 Contra
Final Polishing MBL Polishing Pad 1µ WP Diamond Suspension Blue 15 4 150 Contra

Magnification: 180X (Brightfield)

sample preparation for AISI 4140 Low alloy steel

Material: Alumina

Results: In this slip-casted and sintered alumina grain structure is easily seen. Due to high hardness level, diamond grinding pads can also be used for grinding operation.

Etching: Phospheric Acid (boiling)

Cutting: SERVOCUT A-250 Cut-off machine with ø250 D126B Diamond cut-off wheel.

Mounting: Ecopress 100 Automatic Mounting Press with Hard Black Epoxy resin

Mechanical Preparation: DIGIPREP 251 Fully automated grinding and polishing system.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Diamond Grinding Disc 220 Grit Water 25 Until Plain 250 Contra
Grinding Diamond Grinding Disc 600 Grit Water 25 2 300 Contra
Fine Grinding. Diamond Grinding Disc 1200 Grit Water 25 1 300 Contra
Pre Polishing Fine Grinding disc Green 3µ WP Diamond Suspension Blue 15 4 150 Contra
Final Polishing MBL Polishing Pad 1µ WP Diamond Suspension Blue 15 1 150 Contra

Magnification: 800X

sample preparation for Alumina

Material: AA7075 Aluminium, wrought

Results: The microstructure of heat treated AA 7075 alloy has elongated grains in the cold working direction. The difference in the colour is due to the different grain orientations.

Etching: 10gr. NaOH+100ml H2O

Cutting: General Purpose BC80NBK Silicon Carbide cut-off wheel. TRENO-NF Silicon Carbide cut off wheels can also be used.

Mounting: Ecopress 100 Mounting Press with Black Phenolic Hot Mounting Resin

Mechanical Preparation: DIGIPREP 251 Fully automated grinding and polishing system.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Diamond Grinding Disc 220 Grit Water 25 Until Plain 250 Contra
Grinding Diamond Grinding Disc 600 Grit Water 25 2 300 Contra
Fine Grinding. Diamond Grinding Disc 1200 Grit Water 25 1 300 Contra
Pre Polishing. Fine Grinding disc Green 3µ WP Diamond Suspension Blue 15 4 150 Contra
Final Polishing CHEM-H Polishing Pad COL-K NC Water 15 1 150 Contra

Magnification: 90X (Polarized Light)

sample preparation for AA7075 Aluminium, wrought

Material: Chilled Cast Iron

Results: Chilled zone has a lighter colour and the remaining darker area is gray iron.

Etching: 3% Nital

Cutting: General Purpose 8A80NBK Aluminium Oxide cut-off wheel. TRENO-H Aluminium Oxide cut off wheels can also be used.

Mounting: Ecopress 100 Mounting Press with Black Phenolic Hot Mounting Resin

Mechanical Preparation: FORCIPOL 2V Grinding / Polishing Machine + FORCIMAT Automatic Specimen Mover.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Met Disc Paper 180 Grit SiC Water 25 2 min. or until plane 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 400 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 800 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 1200 Grit SiC Water 20 2 250 Contra
Bramet Disc Paper
Final Polishing MRE Polishing Pad Alpha Alumina. 1µ Powder Water 15 4 150 Comp.

Magnification: 300X (Brightfield)

sample preparation for Chilled Cast Iron

Material: Cu-Au Coating on watch band

Results: The coating layer is clearly visible and can be measured easily. In order to prevent coating material from breaking, the sample has been cold mounted before cutting.

Cutting: MICRACUT 125 Precision Cut-off machine with ø150 CBN Cutting wheels

Mounting: Cold Mounting Epoxy VLT

Mechanical Preparation: FORCIPOL 2V Grinding / Polishing Machine + FORCIMAT Automatic Specimen Mover.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Met Disc Paper 180 Grit SiC Water 25 2 min. or until plane 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 400 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 800 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Pre Polishing MRE Polishing Pad 6µ WP Diamond Suspension Blue 15 3 150 Contra
Final Polishing MBL Polishing Pad 1µ WP Diamond Suspension Blue 15 3 150 Contra

Magnification: 400X

sample preparation for Cu-Au Coating on watch band

Material: DIN 1.2344 Hot Work Tool Steel

Results: In nitrited surface, the white layer and the diffusion zone underneath are clearly seen. Case depth is approx. 50 microns and the hardness is 110º kg/mm². Low cutting force with lower feed is recommended. Edge roundness should be avoided.

Etching: 10% Picric Acid + 100 ml. Ethanol

Cutting: General purpose 8A80KBK Aluminium Oxide cut-off wheel. TRENO-S Aluminium Oxide cut off wheels can also be used.

Mounting: Ecopress 100 Automatic Mounting Press with Black-Epoxy (600811)

Mechanical Preparation: FORCIPOL 300-1V Grinding / Polishing Machine + FORCIMAT Automatic Specimen Mover.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Met Disc Paper 180 Grit SiC Water 30 2 min. or until plane 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 400 Grit SiC Water 25 2 250 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 800 Grit SiC Water 25 2 250 Contra
Bramet Disc Paper
Pre Polishing MST Polishing Pad 6µ WP Diamond Suspension Blue 15 3 150 Contra
Final Polishing MSF/MSFL Polishing Pad 1µ WP Diamond Suspension Blue 15 4 150 Contra

Magnification: 180X (Brightfield)

sample preparation for DIN 1.2344 Hot Work Tool Steel

Material: Glass

Results: The calsium carbonate crystal on the corroded surface of a glass.

Cutting: DIMOS Diamond cut-off wheels

Mounting: Cold Mounting and Embedding Form

Mechanical Preparation: DIGIPREP 251 Fully automated grinding and polishing system.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Diamond Grinding Disc 220 Grit Water 25 Until Plain 250 Contra
Grinding Diamond Grinding Disc 600 Grit Water 25 2 250 Contra
Fine Grinding. Diamond Grinding Disc 1200 Grit Water 25 3 300 Contra
Pre Polishing Fine Grinding disc Green 3µ WP Diamond Suspension Blue 15 4 150 Contra
Final Polishing MBL Polishing Pad 0.25µ WP Diamond Suspension Blue 15 4 150 Contra

sample preparation for Glass

Material: Glass

Results: The defect on the surface of a glass.

Cutting: DIMOS Diamond cut-off wheels

Mounting: Cold Mounting and Embedding Form

Mechanical Preparation: FORCIPOL 1V Grinding / Polishing Machine +FORCIMAT Automatic Specimen Mover.

Parameter / Stage Surface Abrasive Lubricant Force per Sample, (N) Time min. Disc Speed, rpm Relative Rotation
Planar Grinding Met Disc Paper 180 Grit SiC Water 30 2 min. or until plane 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 400 Grit SiC Water 30 2 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 600 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 800 Grit SiC Water 25 2 300 Contra
Bramet Disc Paper
Fine Grinding. Met Disc Paper 1200 Grit SiC Water 20 2 250 Contra
Bramet Disc Paper
Final Polishing MBL Polishing Pad 0.25µ WP Diamond Suspension Blue 15 4 150 Contra

sample preparation for Glass