TECHNOLOGY FOR MACHINING HIGH-REFRACTORY CERAMIC PARTS
BASED ON SILICON NITRIDE
V. V. Kuzin
Translated from Novye Ogneupory, No. 8, pp. 19 – 24, August, 2006.
Original article submitted July 10, 2006.
The results of the experimental study of mechanical treatment of highly refractory ceramic parts made of vari
ous compositions based on silicon nitride are described. The revealed regularities of the surface layer and de
fect formation have been used to develop a two-stage process for working these parts, which ensures high ma
chining efficiency and a minimum level of surface layer defects. The proposed technology has been used in
making cutting plates from nitride ceramics, which has increased their average resistance by 15 – 20%.
The service reliability of parts made of highly refractory
silicon nitride ceramics to a large extent depends on the type
and conditions of their machining . These parts are usually
worked by diamond grinding, which produces an enhanced
force and thermal impact on their surface layer. Large
stresses are formed in the surface layer of the part under
loading, which generates cracks and local fractures . Such
technological defects significantly modify the structure and
properties of the surface layer of high-refractory ceramic
parts, which is eventually reflected in their service parame-
ters. The number of defects in the surface layer of ceramic
parts could be reduced by decreasing the grinding parameters
and, accordingly, lowering the grinding efficiency. However,
this substantially increases the cost of the parts, which in
some cases is unacceptable.
A technology for treating parts made of highly refractory
silicon nitride ceramics intended to minimize the number of
surface defects has been developed involving a rational
choice of a kinetic scheme and regimes of treatment, as well
as design and parameters of diamond tools meeting the pre
set efficiency and service parameters of ceramic parts. The
proposed two-stage process of mechanical treatment of
high-refractory silicon nitride parts includes highly efficient
diamond grinding (Fig. 1a ) and subsequent lapping of the
surface with a free abrasive (Fig. 1b ). Lapping was chosen
as the final stage of treatment, since it yields the best rough
ness parameters (R
< 0.05 mm) and an optimum profile of
the treated surface, which has a positive effect on the service
parameters of the parts [3, 4]. Therefore, in our study we an
alyzed the correlation of diamond grinding and free abrasive
lapping parameters with the morphology and roughness of
flat surfaces, as well as the bending strength of silicon nitride
ceramics of different compositions.
Refractories and Industrial Ceramics Vol. 47, No. 4, 2006
1083-4877/06/4704-0204 © 2006 Springer Science+Business Media, Inc.
Fig. 1. Schemes of diamond grinding and free abrasive lapping of
ceramic samples based on silicon nitride: v
) rotational speed of the
) rotational speed of the lap; S
) lateral feed; S
dinal feed; t ) grinding depth, O) sample; L) lap.
Stankin Moscow State Technical University, Moscow, Russia.