Structure news · # 19 · December 2014
Structure
news
Comparing Different Preparation
Techniques for the Characterisation
of Niobium carbides
Authors:
www.struers.com
In this issue
Comparing different preparation
techniques of Niobium carbides1
Redesigning ductile
plane grinding surfaces2-3
e-Seminar Q & A
4
e-Seminars 2015
5
M. Scheibe, S. Binkowski, S. Benemann, R. Saliwan-Neumann
This article was first published by BAM Bundesanstalt für Materialforschung und -prüfung,
DE-12200 Berlin, Germany
Abstract
Electronic imaging analytic methods like SEM-EDX, FESM or EBSD
enable with the first characterization a definite and direct insight on
composition, components and other characteristics of a sample.
Especially for new materials these characteristics are often unknown
and micro structures may be very fine. Materialographic steps like
cutting, grinding and polishing are still necessary. Based on results
of the above mentioned methods classic metallographic preparation
steps can be aligned to the characteristics of new materials. So for
non-bond and metal bond NbC’s a complete and descriptive structure
analysis is also possible with “classic” metallographic methods.
You can read the full article here:
English version
http://www.struers.com/article-niobium_carbides_EN
German version
http://www.struers.com/article-niobium_carbides_DE
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1
Structure news · # 19 · December 2014
Structure
news
Redesigning ductile plane grinding surfaces
Author:
Thomas Nørbygaard, Ph.D., R&D Department, Struers A/S
Creating an abrasive surface for metallographic plane grinding
of ductile materials is not an easy task. Ever since the launch of
the MD-Piano, Struers successful diamond disc for hard materials grinding, there has been increasing demand for an equally
useful disc for ductile materials: A hard surface with integrated
abrasives, durable and designed for multiple uses, giving
extremely flat surfaces and finally providing an alternative to
the well-known but somewhat tedious SiC Paper/Foil solution.
Many attempts have been made to create a general plane
grinding solution for ductile materials. However, it has not been
easy to find a solution that can really compete with SiC Paper/
Foil in a broad sense. First and foremost because “ductile materials” are very far from being a homogenous group and trying
to encompass all these different materials requires prioritizing
opposing requirements for the surface.
Aluminium - Silicon Cast
Grinding
Step
PG
FG
Surface
MD-Molto
MD-Largo
Abra- Type
sive Size
Diamond
Diamond
#220
9 μm
Suspension /
Lubricant
Water
DiaPro Allegro/
Largo
Rpm
300
150
Force (N)/
specimen
25
30
Time (min)
Until plane
4
Step
DP
OP
Surface
MD-Mol
MD-Chem
Abra- Type
sive Size
Diamond
Collodial Silica
3 μm
0.04 μm
Suspension /
Lubricant
DiaPro Mol R
OP-U NonDry
Rpm
150
150
Force (N)/
specimen
25
15
Time (min)
3
1
This approach eventually leads to a mediocre surface that may
be applicable for a big range of target materials, but is not really
great for any of them. Instead we started focusing on the key
difficulties and requirements for smaller material groups:
MD-Molto – The grinding disc for aluminum
As is well known, it is generally easy to grind aluminium and
aluminium alloys. SiC Paper/Foil is highly efficient on aluminium
and just about any abrasive surface, (including those designed for
ferrous metals and ceramics), is able to grind aluminium – usually
with decent to good removal rates as well. Most tools, however,
are not up to this task for long. Huge, aggregated aluminium chips
eventually become stuck on the tool surface or cover the abrasives,
impeding further grinding or causing extreme wear. Surfaces that
might last for hours when grinding steels will suddenly wear down
in a few minutes when grinding aluminium.
Struers new aluminium disc is based on coated diamonds, which
gives the most durable combination of wear properties and
retention of abrasives. It features filler grains to stabilize the resin
matrix, special additives added to minimize chip clogging and
finally a new massive pattern designed for chip clearance and
longevity. The removal rate of the disc is modest (compared to
other, more aggressive surfaces), but still sufficiently high to allow
a plane grinding operation in about one minute using low grinding
forces. The disc is self-dressing, gives constant performance
throughout, and with a disc life of 100 + operations, plane grinding
of aluminium has never been easier or more convenient.
Polishing
Fig. 1: Aluminium-silicon cast, refined, bright field, 500x.
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Structure
news
Structure news · # 19 · December 2014
MD-Mezzo – The grinding disc for titanium alloys
Developing a plane grinding disc for titanium called for a
completely different focus. Here the difficulty lies in raising the
removal rate to tolerable levels, as titanium resists deformation
Preparation Method
Grinding
Step
PG
FG
SurfaceMD-Mezzo MD-Largo
Abrasive
Type
Size
DiamondDiamond
#220
9 μm
Suspension/ Water
Lubricant
DiaPro
Allegro/Largo
rpm300
150
F orce [N]/
specimen
40 *
30
Time (min)
Until Plane
5
and abrasive processing very efficiently. SiC Paper/Foil is the
standard tool of choice for titanium, but even these surfaces
struggle, requiring many minutes and multiple paper shifts,
when plane grinding massive titanium specimens.
In the new multilayer surface for titanium we find that once
again coated diamonds are the superior choice of abrasive to
keep a constant, high performance. Removal is boosted by a
combination of relative high grinding force, a customized resin
matrix ingredient and an aggressive pattern. This allows for
average removal rates beyond that of SiC Paper/Foil, combined
with the superior flatness you only get from a hard surface.
Despite the rough grinding conditions, disc life is substantial
allowing for 100 + plane grinding operations of solid titanium
alloy specimens.
With two new discs launched in 2014 we hope to help users
all over the world improve their plane grinding procedures for
aluminium and titanium alloys.
Polishing
Step
OP
SurfaceMD-Chem
Abrasive
Type
Size
Suspension /
Lubricant
Collodial Silica
0.04 μm
OP-S**
rpm150
Force [N]/
specimen
30 per sample
Time (min)
5 ***
Table 1 shows a general, automatic preparation method for titanium and its alloys
with 6 unmounted samples, 30 mm dia. clamped in a holder. Please be aware that the
polishing time can vary depending on the purity of the titanium and the area of the
sample surface.
* Decrease to 25 N to aviod pencil shapes in single sample preparation.
** Mix 90 ml OP-S with 10 ml H2O2 (30%).
*** T he polishing time depends on the sample area. Very large
samples require more polishing time than small ones.
Fig. 2: Titanium alloy-Ti6Al5V, polarized, 200x.
3
Structure news · # 19 · December 2014
Structure
news
Struers e-Seminar Q&As
by Birgitte Nielsen,
Application Specialist, Struers A/S
Q: Are there any way out for clay ore?
A: Preparing water sensitive minerals is a delicate matter
as both equipment and consumables have to be suitable for
operating “water-free”.
Water free cutting fluid as well as alcohol based lubricant for
grinding and polishing processes are available from Struers.
Q: Impregnation of soils and loose sediments. Which type of
resins are best used for impregnating soils and loose sediments
generally?
A: It is extremely important that the material/soil is absolutely
degreased and dry before mounting!
And the best mounting method to get a good impregnation and
adhesion is to use vacuum impregnation with an epoxy resin.
One method to clean material before mounting is the “Soxhlet
Extractor”[1].
Q: What is the refraction index for the UV curable adhesive
you mentioned?
A: The epoxy ideally has an refraction index of 1.54.
Struers EpoFix is 1.58 and EpoSpeed 20 (UV curable) is 1.56.
[1] A Soxhlet extractor is a piece of laboratory apparatus invented in 1879
by Franz von Soxhlet. It was originally designed for the extraction of a
lipid from a solid material. However, a Soxhlet extractor is not limited to
the extraction of lipids. Typically, a Soxhlet extraction is only required
where the desired compound has a limited solubility in a solvent, and
the impurity is insoluble in that solvent. If the desired compound has a
significant solubility in a solvent then a simple filtration can be used to
separate the compound from the insoluble substance.
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Structure news · # 19 · December 2014
Structure
news
e-Seminars 2015
Struers conducts e-Seminars every month. The e-Seminars cover various topics related to the materialographic world and give
you a chance to ask the Struers metallographer questions on the covered topic. If you are unable to participate in an e-Seminar,
you can register and see recordings of previous e-Seminars.
e-Seminar on Preparation of Titanium
27/1
e-Seminar on Materialographic etching
3/2
e-Seminar on Mineralographic processes - New “Mineralogram”
10/3
e-Seminar on Electrochemical preparation
14/4
e-Seminar on Welding inspection
12/5
e-Seminar on Clamping
23/6
e-Seminar on Materialographic troubleshooting
8/9
e-Seminar on On-site preparation
13/10
e-Seminar on Hot mounting
10/11
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