Ngk Spark Plug Company, Limited

Junichiro Suzuki

Shoji Sakakibara

Masakazu Watanabe

Akiyasu Okuno

Yoshihiro Yamamoto

Minoru Nakamura

Hiroshi Tanaka

Hideki Kato

Tatsuji Kinukawa

Masahide Kayukawa

Hajime Yasui

Si.sub.3 N.sub.4 based ceramics are prepared by molding, calcining and sintering a powder mixture of columnar-shaped Si.sub.3 N.sub.4 particles having a particular size, a minor quantity of sintering aids and equiaxed Si.sub.3 N.sub.4 particles. The ceramics have a structure containing a specific quantity of coarse columnar grains grown from the coarse columnar-shaped particles as seed crystals, and superior in wear resistance, resistance to chipping and thermal resistance, and useful as wear resistant components or cutting tools. The ceramics can be produced without recourse to hot press sintering by normal sintering or sintering under a gas pressure, or further by applying HIP.

Method for preparing silicon nitride based ceramics

A ceramic cutting tool of a TiC-based sintered body containing 40 wt % or more of TiC, and 5 to 40 wt % of SiC whisker uniformly dispersed in the sintered body, said SiC whisker having a diameter of 0.2-1.5 .mu.m and a length of 1-20 .mu.m. The sintered body may include up to 40 wt % of Al.sub.2 O.sub.3, and may further contain sintering aid. Up to 40% by weight of TiC may be substituted with at least one of Ti, nitrides, oxides and borides of Ti, and solid-solution of said nitrides, oxides and borides of Ti to form a TiC-base composition. The TiC-base composition may be represented by (Ti.sub.a M.sub.b) (C.sub.c N.sub.d O.sub.e B.sub.f).sub.g where: M denotes at least one of transition metal elements of Groups IVa, Va and VIa, except Ti, according to the International Periodic Table; and a+b=1, 0&lt;b.ltoreq.0.5, c+d+e+f=1, 0.5 .ltoreq.c.ltoreq.1.0, 0.ltoreq.d.ltoreq.0.5, 0.ltoreq.e.ltoreq.0.3, 0.ltoreq.f.ltoreq.0.5, 0.6.ltoreq.g.ltoreq.1.1.

Process for making TiC-base/SiC whisker composite ceramic cutting tools

A ceramic cutting tool formed of a TiC-based sintered body contains 40 wt % or more of TiC, and 5 to 40 wt % of SiC whisker uniformly dispersed in the sintered body. The SiC whisker has a diameter of 0.2-1.5 .mu.m and a length of 1-20 .mu.m. The sintered body may contain up to 40 wt % of Al.sub.2 O.sub.3, and further sintering aids. Up to 40% by weight of the TiC may be substituted with at least one of Ti, nitrides, oxides and borides of Ti, and solid-solutions of these nitrides, oxides and borides of Ti to form a TiC-base composition. The TiC base composition may be represented by the formula (Ti.sub.a M.sub.b) (C.sub.c N.sub.d O.sub.e B.sub.f).sub.g, in which M denotes at least one transition metal element of Groups IVa, Va and VIa according to the International Periodic Table, except Ti; and a+b=1, 0&lt;b.ltoreq.0.5, c+d+e+f=1; 0.5 c.ltoreq.1.0; 0.ltoreq.d.ltoreq.0.5; 0.ltoreq.e.ltoreq.0.3; 0.ltoreq.f.ltoreq.0.5; and 0.6.ltoreq.g.ltoreq.1.1.

TiC-base/SiC whisker composite ceramic cutting tools

A silicon nitride body having a surface portion comprising .alpha. sialon, or .alpha. sialon and .beta. sialon wherein the ratio of .alpha. sialon relative to the sum of .alpha. sialon and .beta. sialon is at least 0.6; and an inner portion comprising .beta. sialon, or .alpha. sialon and .beta. sialon, wherein the ratio of .beta. sialon relative to the sum of .alpha. sialon and .beta. sialon is at least 0.6.

Silicon nitride base sintered body

A sintered body of silicon nitride base solidly formed of interior and surface portions wherein the rate of decrease of the content Si or Si.sub.3 N.sub.4 and Sialon grains in the surface portion, with respect to that in the interior portion, is not less than 20% by weight or 30-100 vol %, respectively. The grain boundary phase of the surface portion is glassy, or crystallized partly or entirely. Crystallized boundary phase comprises Si.sub.3 N.sub.4 -Y.sub.2 O.sub.3 base compounds Si.sub.3 N.sub.4 -nY.sub.2 O.sub.3 -mX (n=1-5, X=SiO.sub.2, Al.sub.2 O.sub.3, m=0-4) such as mellilite, J phase (mohlerite), K phase (wollastonite), H phase (apatite), or A phase (Si.sub.3 N.sub.4.5Y.sub.2 O.sub.3.Al.sub.2 O.sub.3). Sintering aids of Al.sub.2 O.sub.3, Y.sub.2 O.sub.3, AlN, MgO, CaO, Y.sub.2 O.sub.3 and/or rare earth oxides form boundary phases. The sintered body may comprise 30% by weight or less of compounds (oxide, carbide or nitride) of subgroups IVa, Va and VIa of the International Periodic Table as third dispersed component. This sintered body with the modified surface portion exhibits the intrinsic property of the interior portion and the property of the surface portion resulting in high wear resistance and toughness useful as cutting tools.

A process for preparation of heat-resistant and wear-resistant ceramic material which comprises sintering the material under a non-oxidizing atmosphere until the metal of a component (a) no longer exists as a metallic phase. A starting composition for forming the ceramic material comprises from 1 to 40 wt % of Al.sub.2 O.sub.3, from 0.05 to 8 wt % of sintering assistant, from 3 to 35 wt % total of one or both of ZrO.sub.2 and HfO.sub.2, and from 17 to 95.95 wt % of carbide components (a) and (b), or (a), (b), and (c), wherein component (a) is one or more metals selected from the Groupd IVB, VB, and VIB of the Periodic Table; component (b) is TiC, and component (c) is one or more metal carbides selected from Zr, Hf, and metals of Groups VB and VIB of the Periodic Table.

Process for the preparation of a heat-resistant and wear resistant

Process for producing highly tough ceramics

A cermet contains 70 to 95 volume percentage of a hard dispersed phase and 30 to 5 volume percentage of a binder phase comprising one or more metals in group VIII (the iron group), wherein the hard dispersed phase contains as its components transitional metals in group IVb, transitional metals in group Vb, W alone of transitional metals in group VIb, C, and N, and consists of two structurally different types of particles. One type of the particles are single phase particles constituting 5% to 50% of the hard dispersed phase, whereas the other type of the particles are dual phase particles constituting 95% to 5% of the same. The cermet is for use in tools such as coating tools, spike pins, hobs, reamers, screw drivers, and so forth.

Cermet for tool

Heat- and wear-resistant ceramic materials is produced by sintering a composition until Ti cannot be detected as the metallic phase, said composition comprised of 5 to 40% by weight of Al.sub.2 O.sub.3, 0.05 to 4% by weight of a sintering aid and 56 to 94.95% by weight of a TiC component in which 4 to 30% by weight of TiC are substituted with Ti.

Process for the production of ceramic materials having heat and wear

A titanium nitride base cermet with high toughness comprises, by weight, 42 to 95% of TiN, 2 to 20% of one or more of Mo, W and the carbides thereof, 2.85 to 30% of an Ni, Co or a mixture thereof, and 0.15 to 8.0% of Al.sub.4 C.sub.3, with the balance being inevitable impurities, wherein half or less of TiN may be replaced with one or more of the carbides and/or carbonitrides of metals from the Groups IVa and Va of the periodic table, with the proviso that the amount of TiN is no less than 30% in the cermet.

Titanium nitride base cermets with high toughness

A process for producing titanium nitride base cermet with a high toughness comprises the steps of:

Process for producing titanium nitride base cermets with high toughness

A method of making a coated tip for cutting purposes having a lower degree of flank and crater wear and reduced chipping. A WC-based ultrahard alloy containing WC, at least one nitride selected from among TiN, TaN and NbN and a bonding metal is heat treated at a temperature of 800.degree. C. to 1,300.degree. C. in a nitrogen atmosphere for a sufficiently long period of time to cause nitride in a layer in the vicinity of the surface of the alloy to move to the surface to form a layer of nitride thereon as well as an alloy layer of WC and the bonding metal in which the nitride has been reduced. The surface of the tip is then coated with a layer of Al.sub.2 O.sub.3.

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Gifu, Japan

Junichiro Suzuki