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Results
The results of the test according
to ASTM G 75-07 show major
advantages with spherical carbides,
picture 8. A significant difference
between the broken FTC and TC
cannot be determined.
One reason for the good results
with spherical carbides lies in the
0
relatively low load, which leads to the
fact that the softer matrix between
the carbides is mostly washed out,
while the carbides themselves are
struck relatively lightly, Picture 9. The spherical carbides
stay longer in the matrix form-closed , since they can only
fall out, in case the matrix is worn out deeper than the
sphere radius. Due to the irregular form and distribution
of the broken FTC and TC, these can fall out more quickly,
since in this case the supporting effect of the matrix is not
given.
The tests on the material according to ASTM G65-04
very clearly show the different influences, such as grain
size, line pitch and type of carbides, picture 10. It becomes
clear that, contrary to the Miller test, the higher contact
pressure of 130 N not only causes the abrasion of the
matrix, but also the demolition of the carbides. In contrast
to the monocrystalline TC, the FTC is lightly dissolved at
the border areas during build-up welding, which enables
a better connection to the matrix material. In addition the
Issue 04 | 2010
Abtrag in mm³
12
10
8
6
4
2
TRANSFER OF TECHNOLOGY
8,80 9,33 7,57 7,79 8,05
9,32
1 2 3 4 5 6
Werkstoff
Pic. 9:
Wear pattern ASTM G75-07 (left: material 3, right: material 6)
Pic. 8:
Results of the ASTM G75-07 Millertest
TC is considerably more brittle and therefore breaks more
quickly. Due to the chosen mass ratio during mixing of the
powder, the coating layer contains less carbides in terms of
numbers with increasing carbide sizes. The influence of the
line pitch is illustrated in material 5, Picture 11. According
to the standard the quartz sand used in the test setup has
a grain size of 200 to 425 µm. Since with Material 5 the line
pitch partly exceeds 200 µm, here the abrasive good can
fully damage the matrix, which leads to an increased drop
out of the FTC spheres.
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