Feldmuhle Aktiengesellschaft

Feldmuehle Aktiengesellschaft

Ulf Dworak

Hans Olapinski

Dieter Fingerle

Ulrich Krohn

Kilian Friederich

Wolfgang Burger

Bengt N Palm

Martti J Hakulinen

Hans Jud

Combinations of frictional and sealing elements made from hard substances, such as sintered aluminum oxide, are ground and lapped at their surfaces of engagement. At least one surface has at least some micro-blurred areas. The micro-blurring is produced by chemical etching. Phosphoric acid can be used as the chemical etching, and in thermal etching, the etching temperature is between 1400.degree. and 1560.degree. C.

Method of etching ceramic frictional or sealing elements

The present invention is in a sintered molding of partially stabilized zirconium oxide having a microstructure of 40 to 70 volume percent cubic phase, 30 to 70 volume percent tetragonal phase, and up to 10 volume percent monoclinic phase wherein the tetragonal phase is present in the form of precipitates less than 200 nm. A mixture of magnesia and yttria is used to stabilize the zirconia. Optionally, the sintered molding may further contain up to 20 wt. % spinel.

Sintered molding, a method for producing it and its use

Disclosed is a starting mixture for the preparation of a sintered body on a basis of aluminum titanate consists of more than 46 wt.-% TiO.sub.2, up to 49.5 wt.-% Al.sub.2 O.sub.3, 3 to 5 wt.-% quartz, and less than 0.2 wt.-% impurities, Al.sub.2 O.sub.3 and TiO.sub.2 being present in the weight ratio of 1:0.95 to 1:1.05. The sintered body according to the invention is composed of:

Sintered form body

Disclosed is a cutting tool insert of sintered ceramic intended for machining ferrous materials. The insert contains 7 to 29% by volume of a hard substance, 1 to 15% by volume of a metal oxide compound, and at least 70% by volume of aluminum oxide, and a maximum of 0.3% by volume of impurities.

Cutting tool insert

A tubularly formed valve guide (1) with a bore for a metal valve shank (2) for use in an internal combustion engine comprising a sintered body of a partially stabilized zirconium oxide having a porosity of less than 3%. Even under extreme stress, e.g., in an outlet valve of a high-power engine, but in particular in the blow-off valve of an exhaust gas turbocharger, the valve guide shows a considerably reduced wear as compared to conventional valve guides.

Valve guide for an internal combustion engine

Ceramic shaped articles are disclosed which are formed of dense, non-metallic, mechanically resistant materials and contain eutectic constituents consisting of zirconium oxide, hafnium oxide and at least one other high-melting oxide and mixtures thereof. The composition exhibits excellent hardness, wear properties and bending strength. A method for preparing the articles is also disclosed wherein the appropriate mixture in a hypoeutectic, eutectic, or hypereutectic ratio is heated to its melting point, poured into a preheated mold and cooled.

Sintered ceramic shaped article wholly or predominantly of eutectic

A piston arrangement with a metal shaft, a piston head that is attached to it with a shrink ring, and a member made of partially stabilized zirconium ozide. The top which demarcates the combustion chamber, of the piston head, consists entirely of the member made of partially stabilized zirconium oxide. The bottom of the zirconium-oxide member is a truncated cone and the top of the shaft is a truncated cone. They are surrounded by an annular component that is split into two sections parallel to the longitudinal axis of the piston. The annular ocmponent is secured with an outside shrink ring.

Piston with a member made of partially stabilized zirconium oxide

A thermal insulation lining (1) in the exhaust duct (4) of a cylinder head (5) consists of a sintered compact (2) of ceramic material having an envelope containing or consisting of inorganic fibers.

Thermal insulation lining of ceramic material for a hot gas duct

In a cylinder head (1) of a piston engine, a thermal insulation component having openings for the accommodation of valve seats, spark plugs, and injection nozzles consists of a circular aluminum titanate plate (2) which is shrink-fitted into a planar circular ring of zirconium oxide (12) gripped or shrink-fitted in the cylinder head. The circular plate (2) of aluminum titanate forms the greatest part of the cylinder head bottom (9).

Cylinder head of a piston engine

A piston ring (1) made of ceramic materials for an internal combustion engine comprising a body made by sintering of partially stabilized zirconium oxide (PSZ) which has a porosity &lt;3% and, rolling surface (4) of the piston ring having a centerline average roughness R.sub.a of 0.03 to 0.1 .mu.m. Due to its homogeneous structure, the inventive piston ring avoids the problems of the ceramic/metal bond of known piston rings and, even under high thermal load, does not suffer from thermally induced destruction or welding of the piston ring groove.

Piston ring for an internal combustion engine

In a pre-combustion or turbulence chamber for an internal combustion engine, an inner molded body, defining an inner chamber, is formed of a material having a thermal conductivity of at least 12 W/(m.multidot.K). An outer body is secured to the outer surface of the inner body by shrinking or glueing. The outer body is formed of a thermally insulating ceramic material having a thermal conductivity of less than 10 W/(m.multidot.K). Due to the low thermal conductivity of the outer molded body, the inner molded body is insulated against heat losses. The higher thermal conductivity of the inner molded body has the effect that, in the interior of the pre-combustion or turbulence chamber, the point at which the cold fuel jet impinges during the injection process is only slightly cooled.

Pre-combustion or turbulence chamber for internal combustion engines

In a cylinder head of a piston engine, the surface of the cylinder head facing the combustion chamber is covered by a plate having openings for valves, spark plugs or injection nozzles. The plate consists of mullite containing 2 to 30% by volume of zirconium oxide and/or hafnium oxide embedded therein, plus 0 to 3 mole-percent of oxides of magnesium, calcium or yttrium, with respect to the zirconium and/or hafnium oxide, and of no more than 0.5%, by weight, of other oxidic impurities.

Mullite plate

A machine component is disclosed composed of 3.0 to 25 weight percent of zirconium oxide and/or hafnium oxide which are present in the interior of the machine component at room temperature predominantly in the metastable tetragonal modification and at the surface of the machine component in the monoclinic modification, said machine component having a profile bearing ratio of about 10 to 40% and an center line average surface roughness R.sub.a in the contact area of less than 0.3 .mu.m. The machine components of the present invention are leakproof, exhibit good thermal shock durability and exhibit good frictional engagement characteristics for long periods of time.

Machine component of oxide ceramic material

Cutting tip for metal-removing processing

The ductility of sintered bodies of alumina and like hard substances can be improved without loss in mechanical strength by uniformly distributed individual particles of tetragonal zirconia or hafnia in amounts of 1%-50% by volume if the dispersed particles have an average size of 0.05 to 2 .mu.m.

Growing community of inventors

Baltmannsweiler, Germany

Ulf Dworak