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PACE Technologies metallographic castable mounting consumables
Metallographic Castable Mounting Information



Metallographic Specimen Mounting

The primary reasons for specimen mounting are to better hold the part to be ground and polished, and to provide protection to the edges of the specimen. Secondarily, mounted specimens are easier to fixture into automated machines or to hold manually. The orientation of the specimen can also be more easily controlled by fixturing it and then setting it in place via mounting. Metallographic mounting is accomplished by casting the specimen into a castable plastic material or by compression mounting the plastic under pressure and temperature.


PACE Technologies metallographic castable mounting consumables
Castable Resin Properties

Castable or cold mounting for metallographic mounts

Castable resins are monomer resins which utilize a catalyst or hardener for polymerization. Polymerization results in cross-linking of the polymer to form a relatively hard mount. Castable resins also have the advantage of simultaneously mounting multiple samples at one time for increased throughput. A number of resin systems used for metallographic mounting and include:

-Epoxy resins
-Acrylic (castable) resins
-Polyester (clear) resins

EPOXY ACRYLIC POLYESTER Resin
Type Epoxy resin and hardener Acrylic resin and powder Polyester resin and hardener
Peak Temperature 100-375°F 150°F 100°F
Shore D Hardness 82 80 76
Cure Time 30 minutes to 8 hours 5-8 minutes 6-8 hours
Comments Moderate hardness, low shrinkage, transparent Very fast cure, translucent, some shrinkage Transparent, water clear

PACE Technologies metallographic castable mounting consumables
Epoxy Resins

The most common and best performing castable resins are epoxy based (Figure 4-2). Epoxy resins are typically two-part systems consisting of a resin and a catalyst (hardener). Mixing ratio's vary from ten parts resin with one part hardener to five parts resin with one part by weight of hardener. The advantages of mounting with epoxy resins include:
Metallographic epoxy resin


Epoxy curing times are dependent upon a number of variables including:

  1. Volume of mounting resin (larger mounts cure faster).
  2. Thermal mass of specimen (larger specimens absorb heat and therefore require longer curing time).
  3. Specimen material properties.
  4. Initial resin temperature (higher temperatures cure faster).
  5. Ambient temperature (higher temperatures cure faster).
  6. Relative humidity and shelf life (absorption of water degrades resin and shortens shelf life).
  7. Mounting mold (plastic, phenolic rings, rubber absorb heat differently).

As a general rule, curing times can vary from 30-45 minutes for fast curing epoxies up to 24 hours for slower curing epoxies. For metallographic epoxies to grind properly, the hardness needs to be at least a Shore D80. Note that epoxy resins typically will continue to harden over a longer period of time (maximum hardness, Shore D90).

In some cases, the curing time and temperature may need to be controlled to compensate for the above variables. For example, an 8-hour resin system can be cured in 30-45 minutes by preheating the resin to approximately 120°F (50°C) prior to mixing and then curing at room temperature. This procedure initiates the catalytic reaction sooner; however, this may also increase the maximum exotherm temperature.

TIP: Preheat the specimen to initiate the epoxy resin at the surface of the mount and thus have the epoxy shrink towards the sample for better edge retention.

Conversely, the resin curing cycle can be slowed or reduced by decreasing the curing temperature by forcing air over the curing mounts (fume hood or fan), placing the mounts into a water bath, or curing in a refrigerator. In these cases, care must be taken to not stop the reaction; however if this does occur or the resin is too soft after curing, heating it to 100-120°F for several hours should push the reaction to completion and the mount should be hard after cooling to room temperature.

Epoxy Standard Epoxy Quick Mounting Epoxy Low Viscosity Epoxy
Characteristic Lower cost Fast cure Lower viscosity, clearer,
lower exotherm, low shrinkage
Cure Time 1-5 hours 30 minutes 2 hours
Mixing ratio (weight)
(resin : hardener)
5:1 10:1 10:1
Peak Exotherm
-20 grams
-30 grams

300°F
350°F

350°F
375°F

120°F
150°F
Color

Clear to slight
yellow tint

Slight yellow tint Clear
Viscosity Medium Medium Low
Shrinkage Moderate High Low

PACE Technologies metallographic castable mounting consumables
Acrylics (Castable)

- Castable acrylics are easy to use and are very robust. The main advantage of mounting with castable acrylics is the fast curing time. Depending upon the mixing ratio, castable acrylic mounts are typically ready to use within 8-15 minutes. Also unlike epoxy resins, the ratio of the various acrylic parts (powder to liquid) can be altered by up to 25% with no adverse effect to the final properties of the mount. This is because both the liquid and powder are acrylics with various additives and curing agents. By varying the ratio of the liquid to powder, the curing time and viscosity can be altered.

Metallographic acrylic resin

Note: The powder contains a catalyst that reacts with the liquid hardener to start the curing process. Fillers are added to increase hardness and to reduce shrinkage.

Characteristics of Acrylics

TIP: Acrylics can be submerged into a water bath during curing. This reduces the exotherm heat and thus reduces the shrinkage of the mount at the specimen interface. A secondary advantage is that the water absorbs the odor.

Acrylic CASTAMOUNT PREMIUM SUPERMOUNT
Characteristic Fast, clear, low shrinkage Fast, clear, low shrinkage Fast, hard
Cure time 10 minutes 8 minutes 10 minutes
Mixing ratio (volume)
Powder : Liquid
3:2 or 2:1 for lower viscosity 3:2 3:2
Color Semi-clear Semi-clear Gray to black

PACE Technologies metallographic castable mounting consumables
Polyesters

Polyesters are typically used when a very clear mount is required. Polyester resins are also useful for mounting parts for display. In this case, the part appears suspended in the plastic. The procedure for molding samples for display is to first determine the mixing ratio of the resin to hardener (catalyst). This ratio is variable depending upon the mass of the casting.

Single Layer Casting (metallographic) CASTAMOUNT
Layer Thickness Drops of catalyst per ounce of resin Layer Drops fo catalyst per ounce of resin
1/8" 15 1st layer 5
1/4" 5 2 nd layer 4
1/2" 6 3rd layer 3
3/4" 5 4th layer 2
1" - 1-1/2" 4 5th layer or more 2

Polyester clear metallographic resins

For larger volumes, the amount of hardener needs to be reduced significantly. The procedure for suspending the sample in the mount is to pour an initial layer and allow it to pot or gel (do not let it fully cure). The object or specimen is then placed on the initial rubbery polyester layer and another layer of the liquid polyester is poured. Multiple layers can be poured in this fashion if required.

Characteristics of Polyester


PACE Technologies metallographic castable mounting consumables
Castable Mounting Procedures

TIP: Before mixing, preheat resin, hardener and specimen to 30°C (85°F) to expedite curing cycle

Note: This will also increase maximum exotherm temperature.

Vacuum/Pressure Mounting

Vacuum impregnation is a very useful technique used to fill in pores or voids prior to specimen preparation. It is highly useful for thermal spray coatings and other porous samples.

Metallographic vacuum impregnation

The most effective technique is to pour the resin under vacuum and/or apply pressure during the curing cycle (advantages - better infiltration of pores and cracks, more transparent mounts, and fewer air bubbles).

For porous or cracked specimens, the resin can aid in supporting these features. Filling these voids can be difficult depending upon their size, with the smaller voids being much more difficult to impregnate than larger voids. This arises mainly because of the compressibility and volume of air within the void. By applying a vacuum to the specimen and pouring while under vacuum the total pressure of this air can be reduced significantly. Subsequent curing at increased pressures will force (or push) the resin into the voids. Note that the vacuum time on both the resin and specimen should be kept to a minimum in order to minimize degassing of the resin.

PV = nRT (gas law)
P - Pressure
V - Volume
T - Temperature

V(bubble size) = nRT/P
Thus in order to decrease the air bubble size, impregnate at low pressures and cure at higher pressures.

Recommended Procedure:
  1. Place mold and sample into impregnation chamber
  2. Mix castable mounting resin
  3. Place cover on chamber and pull vacuum
  4. Pour resin into mount
  5. Slowly increase the pressure
  6. Allow the mount to cure at room pressure or apply an external pressure.

TIP: Do not pull vacuum for more than 60 seconds. Extended vacuum causes the dissolved gases in the liquid resin to degass and bubble (similar to opening up a carbonated beverage bottle).

TIP: To reduce the curing time, preheat resin, hardener and specimen to 30°C (85°F). Note: this will also increase maximum exotherm.

TIP: Slight preheating of the epoxy will also reduce the viscosity of the resin and allow it to flow better.

PACE Technologies metallographic castable mounting consumables
Trouble Shooting (Castable Resins)

Symptom Cause Action
Lack of or partial curing of resin Improper or insufficient mixing -Remount – taking care to sufficiently mix epoxy resin and catalyst
-Check expiration date on catalyst (typically 1-year)
Soft or gummy resins
(Grinding produces a matted finish)
Insufficient curing of resin – primarily by too low an exotherm Heat mount in an oven at 90-100°F (30-40°C) for 1-2 hours and let cool.
Resin should harden upon cooling

Bubbling, cracking, or yellowing of resin

Too hot a curing exotherm
-Mount at room temperatures below 85°F (30°C)
-Decrease volume or volume percentage of hardener
Too long a curing time Improper resin mixture, old hardener, or too cold a mounting temperature -Replace old hardener
-Mount at room temperatures 70-80°F (30°C)
-Preheat resin but cure at room temperature
Bubbles in resin Improper mixing or degassing of specimen -Mix with a slow folding motion
-Pour resin under vacuum and/or cure under higher pressures
-Clean specimen prior to mounting

PACE Technologies metallographic castable mounting consumables

Castable Resin Consumables

CASTAMOUNT Acrylic (Castable)
Description Quantity Catalog Number Product Image
CASTAMOUNT Acrylic resin kit (1 lb)
CASTAMOUNT Acrylic resin kit (5 lbs)
1 lb resin with 12 oz hardener
5 lb resin with 1/2 gallon hardener
AK-5000-K1
AK-5000-K5
Metallographic castable CASTAMOUNT acrylic

CASTAMOUNT Acrylic
resin powder

1 lb (454 gms)
5 lbs (2.2 kg)
25 lbs
100 lbs

AR-5000-P1
AR-5000-P5
AR-5000-P25
AR-5000-P100

CASTAMOUNT Acrylic hardener (clear liquid)

12 oz (0.36 l)
32 oz
1/2 gallon
1 gallon
5 gallons

AH-5000-H12
AH-5000-H32
AH-5000-H64
AH-5000H128
AH-5000-H640

PACE Technologies metallographic castable mounting consumables



ACRYLIC PLUS (Castable)
Description Quantity Catalog Number Product Image
ACRYLIC PLUS resin kit (1 lb)
ACRYLIC PLUS resin kit (5 lbs)
1 lb resin with 12 oz hardener
5 lb resin with 1/2 gallon hardener
ACYP-5000-K1
ACYP-5000-K5
Metallographic Premium Acrylic

ACRYLIC PLUS
resin powder

1 lb (454 gms)
5 lbs (2.2 kg)
25 lbs
100 lbs

ACYP-5000-P1
ACYP-5000-P5
ACYP-5000-P25
ACYP-5000-P100

ACRYLIC PLUS hardener (clear liquid)

12 oz (0.36 l)
32 oz
1/2 gallon
1 gallon
5 gallons

ACYH-5000-H12
ACYH-5000-H32
ACYH-5000-H64
ACYH-5000H128
ACYH-5000-H640

PACE Technologies metallographic castable mounting consumables



SUPERMOUNT Acrylic kits (with filler)
Description Quantity Catalog Number Product Image
Glass Filled Acrylic kit (1 lb)
Glass Filled Acrylic kit (5 lbs)
1 lb resin with 12 oz hardener
5 lb resin with 1/2 gallon hardener
GKAR-5000-K1
GKAR-5000-K5
Metallographic Supermount Acrylic
Glass Filled Acrylic powder (black) 1 lb (454 gms)
5 lbs (2.2 kg)
GRAR-5000-P1
GRAR-5000-P5
Lliquid hardener (64 oz)

12 oz (0.36 l)
32 oz
1/2 gallon
1 gallon

GRAH-5000-H12
GRAH-5000-H32
GRAH-5000-H64
GRAH-53000-H128

PACE Technologies metallographic castable mounting consumables

EPOXY Resins Consumables

EPOXY Resins
Description Quantity Catalog Number Product Image
Epoxy Resin 32 oz (0.95 l)
1 gallon (3.8 l)
EP-3000-32
EP-3000-128
Metallographic castable Epocast Epoxy
Epoxy Hardener 8 oz (0.24 l)
32 oz (0.95 l)
EH-3000-08
EH-3000-32
1-gallon pump dispenser each ED-3000-01
PACE Technologies metallographic castable mounting consumables



QUICKMOUNT 2 Fast EPOXY Resin
Description Quantity Catalog Number Product Image
QUICKMOUNT Fast Epoxy Resin 32 oz (0.95 l)
1 gallon (3.8 l)
EPF-3000-32
EPF-3000-128
Metallographic Quickmount2 epoxy
QUICKMOUNT Fast Hardener 8 oz (0.24 l)
32 oz (0.95 l)
EHF-3000-08
EHF-3000-32
1-gallon pump dispenser each ED-3000-01
PACE Technologies metallographic castable mounting consumables



ULTRATHIN 2 Low Viscosity EPOXY Resin
Description Quantity Catalog Number Product Image
ULTRATHIN 2 Low Viscosity Casting Epoxy Resin 32 oz (0.95 l)
1 gallon (3.8 l)
ULTRA-3000-32
ULTRA-3000-128
Metallographic Ultrathin2 epoxy
ULTRATHIN 2 Viscosity Hardener 8 oz (0.24 l)
32 oz (0.95 l)
ULTRA-3000H-08
ULTRA-3000H-32
1-gallon pump dispenser each ED-3000-01
PACE Technologies metallographic castable mounting consumables



EPOXY-ELITE (Enviromentally friendly) EPOXY Resin
Description Quantity Catalog Number Product Image
EPOXY-ELITE Casting Epoxy Resin 32 oz (0.95 l)
1 gallon (3.8 l)
ELITE-3000-32
ELITE-3000-128
Metallographic Ultrathin2 epoxy
EPOXY-ELITE Viscosity Hardener 8 oz (0.24 l)
32 oz (0.95 l)
ELITE-3000H-08
ELITE-3000H-32
1-gallon pump dispenser each ED-3000-01

PACE Technologies metallographic castable mounting consumables

POLYESTER Resins Consumables

POLYCAST Clear Polyester Resin
Description Quantity Catalog Number Product Image
Polyester Resin 1 gallon (3.8 l) POLYCAST-128 Metallographic polyester Polycast resin
Polyester Hardener 2 oz POLYHARD-02
Polyester dye kit 3 colors/pkg DYE-1000

PACE Technologies metallographic castable mounting consumables

MISCELLANEOUS Mounting Supplies

Castable Mounting Molds
Description Quantity Catalog Number Product Image
Reuseable two piece
plastic molds
1.25" molds
1.50" molds

12/pkg
12/pkg

METPREP-0125
METPREP-0150
Metallographic 2-piece reusable mounts
Disposable plastic mounting molds
1" molds
1.25" molds
1.50" molds
50/pkg
MOUNT-0100
MOUNT-0125
MOUNT-0150
Metallographic castable disposable mounts
Reuseable Silicon rubber
1-inch diameter
1.25-inch diameter
1.5-inch diameter
2-inch diameter
2.75 x 1.55 x 7/8-inch rectangular
3 x 2 x 7/8-inch rectangular

3/pkg
3/pkg
3/pkg
3/pkg
each
each

RMOUNT-0100
RMOUNT-0125
RMOUNT-0150
RMOUNT-0200
RMOUNT-315R
RMOUNT-302R
Metallographic castaable rubber mounts
PACE Technologies metallographic castable mounting consumables



Miscellaneous Mounting Accessories
Description Quantity Catalog Number Product Image
Mold release 8 oz (0.24l)
16 oz (0.47l)
MR-1000-08
MR-1000-16
Metallographic castable mold release
Stirring sticks
(6" tongue depressors)
100/pkg SS-1000-100 Metallographic stirring sticks
Mixing cups
(3 oz graduated cups)
100/pkg MCUPS-1000-50 Metallographic castable mixing cups
Plastic mixing cups ( 9 oz) 50/pkg PCUPS-050 Metallographic castable plastic mixing cups
Plastic specimen mounting clips

100/pkg

KLIP-0100 Metallographic castable metal mounting clips
Metal specimen mounting clips 100/pkg MKLIP-0100 Metallographic castable metal mounting clips
1.25" specimen storage containers 25/pkg STORE-0125 Metallographic specimen storage holders

PACE Technologies metallographic castable mounting consumables



PACE TECHNOLOGIES CONTACT


PACE Technologies
3601 E. 34th St.
Tucson, Arizona 85713
+1-520-882-6598
FAX +1-520-882-6599
email: pace@metallographic.com
https://www.metallographic.com


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