Sandvik Ab

Abb Cerama Ab

Marianne Collin

Jan Nilsson

Bertil Mattsson

Magnus Ekelund

Mats Andersson

Marian Mikus

The present invention relates to a method for sintering of a silicon nitride based material using gas pressure sintering technique. It has been found that using a sintering atmosphere containing nitrogen and 0.1-10 vol-% carbon monoxide a cutting tool material is obtained with improved properties, particularly increased edge toughness, when machining heat resistant alloys.

Method of sintering silicon nitride based materials

The ceramic cutting tool material according to the present invention comprises a beta silicon nitride matrix with total amount of 0.5-10 weight %, preferably 0.5-6 weight %, of an intergranular phase and 0.05-3 weight % of at least one secondary crystalline phase of a transition metal carbide, nitride, carbonitride and/or silicide present as spherical particles with a size of 0.1-2 .mu.m, preferably submicron (0.01-1 .mu.m). The transition metal is preferably niobium and/or tantalum. The material has less than 1 volume %, preferably less than 0.3 volume %, porosity. The beta silicon nitride grains are to at least 10%, preferably more than 20%, elongated with an aspect ratio greater than 3, preferably greater than 5. The grain diameter of the beta silicon nitride grains is in the range of 0.2-10 .mu.m, preferably 0.2-5 .mu.m, and most preferably 0.2-3 .mu.m.

Process for making silicon nitride cutting tool material

There is disclosed a silicon nitride based cutting tool insert for chipforming machining of cast iron material having improved mechanical, chemical and wear properties. This is obtained by addition of one or more transition metal oxides which act as a sintering aid together with alumina and yttria and also promote the growth of elongated grains of beta silicon nitride during the sintering. Preferably, the inserts are provided with a wear resistant coating as known in the art. The ceramic cutting tool material according to the present invention comprises a beta silicon nitride matrix with total amount of 0.5-10 weight %, preferably 0.5-6 weight %, of an intergranular phase and 0.05-3 weight % of at least one secondary crystalline phase of a transition metal carbide, nitride, carbonitride and/or silicide present as spherical particles with a size of 0.1-2 .mu.m, preferably submicron (0.01-1 .mu.m). The transition metal is preferably niobium and/or tantalum. The material has less than 1 volume %, preferably less than 0.3 volume %, porosity. The beta silicon nitride grains are to at least 10%, preferably more than 20%, elongated with an aspect ratio greater than 3, preferably greater than 5. The grain diameter of the beta silicon nitride grains is in the range of 0.2-10 .mu.m, preferably 0.2-5 .mu.m, and most preferably 0.2-3 .mu.m.

Silicon nitride cutting tool material

There is now provided a ceramic material comprising of alumina, 10-50% by volume, preferably 20-35% by volume, silicon carbide whiskers, 1-25% by volume, preferably 5-20% by volume, most preferably 7-15% by volume, zirconia and 1-20% by volume, preferably 3-15% by volume, titanium compound-containing cubic phase. If this cubic phase has a lattice spacing of 4.29 to 4.40 .ANG. and a zirconium content of 3-65 weight %, a material with improved performance when turning heat resistant material such as aged Iconel 718, is obtained.

Whisker-reinforced ceramic material

A method of manufacturing whisker reinforced ceramic bodies with new and improved properties. By replacing the tool pressing with injection molding, surprisingly a more homogeneous structure and more advantageous whisker orientation has been obtained. By choosing the conditions of the molding, it is possible to control the whisker orientation to get optimal material properties. Bodies according to the invention are particularly suitable for chip forming machining of heat resistant materials.

Method of manufacturing inserts preferably for machining of heat

According to the present invention there is provided a method of manufacturing a compound body having at least one, partly covering layer on a porous body, whose pore system is evacuate by means of a subpressure which is applied on the porous body by a suction cup or the like and the body is dipped in a slurry of powdery components of the layer. The compound body is densified by sintering or other heat treatment, e.g., post-HIP.

Method of manufacturing a compound body and the resulting body

There is now provided a method of manufacturing a coated ceramic body with improved performance when used as a tool insert for metal cutting purposes. By subjecting the body after the coating to a hot isostatic pressing operation at a pressure of 10-300 MPa and a temperature of &gt;1200.degree. C., an improved adherence of the coating has been achieved. The method is particularly applicable to whisker-reinforced ceramic composites.

Method of coating a ceramic body

The present invention relates to whisker reinforced ceramic bodies with new and improved properties. By replacing the tool pressing with injection molding, surprisingly a more homogeneous structure and more advantageous whisker orientation has been obtained. By choosing the conditions of the molding, it is possible to control the whisker orientation to get optimal material properties. Bodies according to the invention are particularly suitable for chip forming machining of heat resistant materials.

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Enskede, Sweden

Marianne Collin