CUTTING FEATURES OF ALMOST UNWORKABLE REFRACTORIES
WITH A DIAMOND TOOL BASED ON A METAL BINDER
A. V. Belyakov
and S. I. Tserman
Translated from Novye Ogneupory, No. 1, pp. 56 – 59, January, 2013.
Original article submitted February 28, 2012.
Cutting features are considered for almost unmachinable materials of the Bakor type with a diamond tool.
A cluster structure is proposed for a diamond-containing layer, which provides a more uniform load on cutting
grains, and this increases segment cutting capacity and improves tool working life.
Keywords: Bakor refractories, cutting refractories, diamond tool, self-sharpening, diamond clusters.
In diamond machining of nonmetals a number of materi
als are separated into an individual group, i.e., almost
unmachinable materials. This is connected with additional
difficulty during grinding, and other forms of diamond treat-
ment, that is expressed in tool blunting, extremely slow ma-
chining rate, and low quality (chips, cracks, high defect con-
centration in surface layers, deviations from rectilinearity).
Materials that are difficult to machine relate natural stone of
class with respect to machinability  (quartzite, ag-
ate, jasper), strong grades of concrete and ferrroconcrete, sin-
gle crystals (sapphire, quartz, silicon), some forms of hard
and strong pore-free ceramic, and also cast and fired
refractories based on, for example, aluminum oxide, zirco
nium dioxide, silicon carbide, and boron carbide.
Cutting features of these hard materials depend on their
structure and physicomechanical properties: high values of
microhardness, strength of component phases, relatively uni
form structure, and porosity close to zero . During dia
mond cutting these materials have a low material breakdown
rate, high energy expenditure on indentation (impression),
and diamond surface scratches, instability of working grain
cutting profile shape . This determines the specific reac
tion of diamond grains with a surface being machined, and
also dynamics of diamond grain denudation from material of
a tool metal matrix, depending on properties of the slurry
During cutting there is breakdown not only of the mate
rial being machined by a tool, but also the tool material itself.
If cutting capacity of a tool is maintained without special
“stripping” (sharpening), then we are talking about a self-
sharpening regime. Normally it is assumed that self-sharpen-
ing involves spontaneous denudation from a tool matrix of
cutting grains by abrasive flow of cutting products. For soft
materials this is often true, but for hard materials the state of
a diamond surface in contact with cut material acquires spe-
Shape changes of cutting grain faces during wear have
been shown in . At first there is formation of a flat area
(flattening) in that area of a diamond in contact with material
during cutting. Then an expansion stage for the flat area
commences, and microcracks and microshears in this area
start to form, which are converted into macrofailure within
the body of a grain, ending in breaking off. A grain only re
tains cutting capacity while configuration of the cutting edge
with formation of a flat area permits indentation (impression)
of diamond into a component under the action of a cutting
force component normal to the surface.
For soft materials cutting forces, created by equipment,
provide breakdown of a surface being machined for a broad
range of angles at the tip of a grain cutting edge, and in this
range its cutting capacity is retained. For hard refractories,
even with small cutting tool edge curvature, diamond ceases
cleaving material and diamond introduction into a surface to
a sufficient depth for breakdown does not occur. Cutting rate
slows down; the volume of material acting on diamond of
each cutting cycle becomes insufficient for spalling of a flat
area of diamond grains; its widening (polishing) continues.
These grains do not cut materials that are difficult to ma
chine, even with significant uncovering of binder from them,
and self-sharpening is connected with restoration and main
tenance of diamond cutting capacity. A microphotograph is
shown as an example in Fig. 1 of a cutting layer surface for a
tool with drilling a hole in cast Bakor refractory. In spite of
diamond grain projection from the matrix, even a little pol
Refractories and Industrial Ceramics Vol. 54, No. 1, May, 2013
1083-4877/13/05401-0051 © 2013 Springer Science+Business Media New York
From proceedings of the International Conference of Refractory
Workers and Metallurgists (29 – 30 March, 2012, Moscow).
FGBOU VPO D. I. Mendeleev Russian Chemical Technology
University, Moscow, Russia.
Company Group Adel’, Zelenograd, Moscow Region, Russia.