Technical Information - Metallographic Abrasive Cutting

Metallographic Abrasive Cutting

ABRASIVE CUTTING


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INTRODUCTION

The first step in preparing a specimen for metallographic or microstructural analysis is to locate the area of interest. Sectioning or cutting is the most common technique for obtaining this area of interest. Proper sectioning has the following characteristics:

  • Flat and cut close to the area of interest
  • Minimal microstructural damage
  • Smeared (plastically deformed) metal
  • Heat affected zones (burning during cutting)
  • Excessive subsurface damage (cracking in ceramics)
  • Damage to secondary phases (e.g. graphite flakes, nodules or grain pull-out)
Sectioning can be categorized as either: Abrasive Cutting and Precision Wafer Cutting. Abrasive cutting is generally used for metal specimens and is accomplished with silicon carbide or alumina abrasives in resin or resin rubber bonds. Proper blade selection is required to minimize burning and heat generation during cutting which degrades both the specimen surface as well as the blade cutting efficiency. Wafer cutting is accomplished with thin diamond blades. Wafer cutting is especially useful for cutting ceramics and minerals as well as some metallic materials.


ABRASIVE BLADE SELECTION GUIDELINES

Selecting the correct abrasive blade is dependent upon the design of the cut-off machine and to a large extent the operator preference. Abrasive blades are generally characterized by bond type and hardness. Determing the correct blade is typically dependent upon the material or metal hardness and and whether it is a ferrous or a non-ferrous metal. In practice, it often comes down to smell and blade life because resin/rubber blades smell more because the rubber will burn slightly during cutting, however resin/rubber blades do not wear as fast and therefore last longer. On the other hand, resin blades generally do not produce the burnt rubber odor, but do break down faster. The resin blades also provide a modestly better cut because the cutting abrasive is continually renewed cuts cleaner.

Also note that in the past that resin/rubber blades have been more popular in the US market, however there has been more of a trend towards resin bonded abrasives. Conversely, resin bonded blades have typically been more widely used in the European market.

SUMMARY:

  • Resin bonded blades - less smell, higher wear, less sample burning
  • Resin/rubber bonded blades - longer life, burnt rubber smell, more likely to burn the sample

    Material
    Recommended Blade
    Soft non-ferrous metals (aluminum, brass, zinc, etc.)
    MAX-E
    Hard non-ferrou metals (titanium, zirconium, etc.)
    MAX-C
    Soft steels
    MAX-E
    Hard and case hardened steels
    MAX-D
    Universal thin resin/rubber blade
    MAX-A
    General Purpose resin blade
    MAX-H

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    ABRASIVE CUTTING PROCESS DESCRIPTION

    Abrasive Sectioning - Abrasive sectioning is primarily used for ductile materials. Examples include metals, plastics, polymer matrix composites, metal matrix composites and rubbers. Proper selection of abrasive blades requires an understanding of the relationship between the abrasive particle, abrasive bonding and the specimen properties.

    • Abrasive Type - Today's high performance abrasive blades use alumina abrasives because alumina is a moderately hard and relatively tough abrasive.
    • Bonding Material - The hardness and wear characteristics of the specimen determine which resin system is the best for abrasive cutting. For hard materials, the specimen wears or breaks down the abrasive, thus to optimize sectioning, new abrasives must be constantly exposed. Therefore softer or more brittle resin systems must break down at a rate similar to how the abrasive fractures or dulls.

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    RECOMMENDED ABRASIVE CUTTING PROCEDURES
    • Select the appropriate abrasive blade
    • Secure specimen - improper clamping may result in blade and specimen damage
    • Check coolant level and replace when low or excessively dirty. Since abrasive blades breakdown during cutting they produce a significant amount of debris.
    • Allow blade to reach its operating speed before beginning the cut.
    • A steady force or light pulsing action will produce the best cuts and minimize blade wear characteristics as well as the maintain sample integrity (no burning).

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    CUTTING FLUIDS

    Lubrication during abrasive cutting and diamond wafer cutting are required to minimize damage and to remove the cutting debris or swarf. For abrasive cutters the proper cutting fluid can have the added benefit of coating the cast iron bases and fixtures to eliminate corrosion and rusting of the cutter.

    Abrasive cutting fluid - The ideal cutting fluid for abrasive cutting is one that removes the cutting swarf and degraded abrasive blade material. It should have a relatively high flash point because of the sparks produced during abrasive sectioning.

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    ABRASIVE SECTIONING TROUBLE SHOOTING
  • Improper sample clamping
  • Too rapid a cut
  • Symptom

    Cause

    Action

    Chipped or broken blade

  • Secure sample properly
  • Reduce cutting force
  • Secure sample properly
  • Reduce cutting force
  • Bluish color on specimen

  • Improper blade or excessive force
  • Consult applications guideline or use a blade with a softer resin

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    ABRASIVE BLADE PRODUCT DESCRIPTIONS

    10-inch bonded Abrasive Blades (32 mm / 1.25-inch arbor)

    Description

    Quantity

    Part No.

    Soft non-ferrous materials (aluminum, brass, zinc, etc.)

    10/pkg

    MAX-E250

    Hard non-ferrous materials

    10/pkg

    MAX-C250

    Soft steels

    10/pkg

    MAX-E250

    Case hardened steels

    10/pkg

    MAX-D250

    Hard steels

    10/pkg

    MAX-D250

    General Purpose

    10/pkg

    MAX-H250

    Universal Thin Blade

    10/pkg

    MAX-A250


    12-inch bonded Abrasive Blades (32 mm / 1.25-inch arbor)

    Description

    Quantity

    Part No.

    Soft non-ferrous materials (aluminum, brass, zinc, etc.)

    10/pkg

    MAX-E300

    Hard non-ferrous materials

    10/pkg

    MAX-C300

    Soft steels

    10/pkg

    MAX-E300

    Case hardened steels

    10/pkg

    MAX-D300

    Hard steels

    10/pkg

    MAX-D300

    General Purpose

    10/pkg

    MAX-H300

    Universal Thin Blade

    10/pkg

    MAX-A300


    14-inch bonded Abrasive Blades (32 mm / 1.25-inch arbor)

    Description

    Quantity

    Part No.

    Soft non-ferrous materials (aluminum, brass, zinc, etc.)

    10/pkg

    MAX-E350

    Hard non-ferrous materials

    10/pkg

    MAX-C350

    Soft steels

    10/pkg

    MAX-E350

    Case hardened steels

    10/pkg

    MAX-D350

    Hard steels

    10/pkg

    MAX-D350

    General Purpose

    10/pkg

    MAX-H350

    Universal Thin Blade

    10/pkg

    MAX-A350


    16-inch bonded Abrasive Blades (32 mm / 1.25-inch arbor)

    Description

    Quantity

    Part No.

    Soft non-ferrous materials (aluminum, brass, zinc, etc.)

    10/pkg

    MAX-E400

    Hard non-ferrous materials

    10/pkg

    MAX-CE400

    Soft steels

    10/pkg

    MAX-E400

    Hard steels

    10/pkg

    MAX-D400

    General Purpose

    10/pkg

    MAX-H400


    Abrasive Cutting Fluid

    Description

    Quantity

    Part No.

    MAXCUT Cutting Fluid (32 oz)

    32 oz

    MAXCUT-1000-32

    MAXCUT Cutting Fluid (1 gallon)

    1 gallon

    MAXCUT-1000-128

    MAXCUT Cutting Fluid (5 gallons)

    5 gallons

    MAXCUT-1000-5G

    MAXCUT 2 Cutting Fluid (32 oz)

    32 oz

    MAXCUT2-1000-32

    MAXCUT 2 Cutting Fluid (1 gallon)

    1 gallon

    MAXCUT2-1000-128

    MAXCUT 2 Cutting Fluid (5 gallons)

    5 gallons

    MAXCUT2-1000-5G


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