FORMATION OF HARD ALLOY VK8 USING TUNGSTEN CARBIDE POWDER
SYNTHESIZED BY MECHANOCHEMICAL TECHNOLOGY
V. P. Reva,
D. V. Onishchenko,
V. V. Petrov,
V. A. Kim,
and A. I. Evstigneev
Translated from Novye Ogneupory, No. 7, pp. 39 – 43, July, 2013.
Original article submitted April 26, 2013.
The possibility is considered of using tungsten carbide powder, prepared by mechanochemical synthesis, as a
material for preparing hard alloy VK8. Results are presented for comparative tests of physicomechanical and
operating properties for hard alloy prepared by different regimes.
Keywords: mechanochemical synthesis, tungsten carbide, hard alloy VK8, sintering regimes, cutting plates.
In the last decade hard alloys have been used extensively
for producing contemporary cutting tools. They consists of
tungsten, titanium, and tantalum carbides secured by a cobalt
binder. Tungsten, titanium, and tantalum carbides exhibit
high hardness, wear resistance, and heat resistance [1, 2].
Tools fitted with hard alloy resist wear by peeling turnings
and billet material, and do not lose their cutting properties
with a heating temperature up to 750 – 1100°C. The cutting
rate for tools fitted with hard alloys exceeds that for tools
made of high-speed steel by a factor of three to four. Hard al
loy tools are suitable for machining hardened steels, and also
nonmetallic materials, such as glass and porcelain. A disad
vantage of hard alloys compared with high-speed steels is
their high brittleness, which increases with a reduction in al
loy cobalt content.
Manufacture of hard alloys concerns primarily the field
of powder metallurgy. Carbide powders are mixed with co
balt powder, then objects of the required shape are pressed
and sintered at a temperature close to the cobalt melting tem
perature. Thus there is formation of hard alloy plates of dif
ferent sizes and shapes, which are fitted to cutters, milling
tools, drills, countersinks, broaches, etc. Hard alloy plates are
fastened in a holder or a body by soldering or mechanically
by means of screws and clamps.
Use of hard alloys based on tungsten carbides makes it
possible to machine metal with ultrahigh cutting rates, since
alloys of this groups exhibit very high hardness, wear resis
tance, and red hardness. Among the priority hard alloys in
demand alloy VK8 should be noted, which is fitted to tools
for drilling, drawing, rough turning of high-temperature and
stainless steels, and also titanium alloys. Alloy VK8 due to
high strength and impact toughness is used for manufactur-
ing hard alloy stamps, operating under conditions of consid-
erable impact loads. The life of hard alloy stamps compared
with steel increases by a factor of 30 – 50, and this provides a
considerable economic effect.
The authors of publications [3 – 5] indicate that amor-
phous carbon, synthesized by pyrolysis from readily renew
able plant raw material (agricultural culture waste and
Sphagnum moss) exhibit a valuable set of physicochemical
properties. In addition, it is an effective carbon agent for per
forming tungsten carbide mechanochemical synthesis. Syn
thesized tungsten carbide has a reduced sulfur content com
pared with carbide prepared using classical carbon agents .
The aim of this work is development of sintering tech
nology for hard alloy VK8, formed from tungsten carbide
powder prepared by mechanochemical synthesis and also a
study of its physicochemical and operating properties.
The main component of hard alloy VK8, i.e., tungsten
carbide was prepared by mechanochemical synthesis in a vi
bration mill . The ultrafine tungsten carbide powder mor
phology is shown in Fig. 1. Tungsten carbide synthesis was
carried out in accordance with the reaction
+3Mg+C=WC+3MgO + Q.
Refractories and Industrial Ceramics Vol. 54, No. 4, November, 2013
1083-4877/13/05404-0295 © 2013 Springer Science+Business Media New York
FGOAU VPO Far Eastern Federal University, Vladivostok,
FGBOU VPO Komsomolsk-on-Amur State Technical University,