Composition of particulate materials and process for obtaining self-lubricating sintered products

A process for obtaining self-lubricating sintered products from a metallurgical composition of particulate materials, the process comprising:

• mixing, in predetermined quantities, particulate materials which define the metallurgical composition;
• homogenizing the particulate material mixture, at a temperature not inferior to that of melting the organic binder;
• granulating the composition to facilitate its handling, storage and supply into an injection machine;
• injection molding the particulate material mixture, so as to provide the mixture with the shape of the product to be sintered;
• extracting the organic binder from the molded piece;
• and
• sintering the conformed mixture, at temperatures from about 1125° C. to about 1250° C., forming, during the sintering, a liquid phase with the particulate alloy element and thus promoting the agglomeration of the solid lubricant in discrete particles dispersed in the volume of a structural matrix, and stabilizing an iron alpha phase of the structural matrix, so as to prevent the dissolution of the portion of the solid lubricant, defined in graphite, in the structural matrix;
• wherein the metallurgical composition of particulate materials comprises,
• a main particulate metallic material, in the form of a main chemical element, wherein the main particulate metallic material is iron, and at least one particulate hardening element, which form the structural matrix in the composite product to be sintered wherein the particulate hardening element has the function of hardening the structural matrix;
• a non-metallic particulate solid lubricant, at least partially soluble in the structural matrix, wherein the particulate solid lubricant is a mixture consisting of graphite and hexagonal boron nitride;
• an alloy component, with the function of stabilizing the iron alpha phase and of preventing the solubilization of the particulate solid lubricant in the iron;
• and
• at least one particulate alloy element capable of forming, during a sintering of a conformed metallurgical composition, a liquid phase between the main particulate metallic material which forms the structural matrix and the particulate solid lubricant, agglomerating the latter in discrete particles;
• wherein the particulate solid lubricant represents a volumetric percentage lower than or equal to 15% of the volume of the composite material to be formed and the particulate hardening element, the particulate alloy element and the alloy component are silicon, at contents from 2% to 5% by weight of the metallurgical composition;
• and
• wherein the main particulate metallic material of iron presents an average particle size lying between about 10 μm and about 90 μm, the hardening element with the function of hardening the structural matrix, and the particulate alloy element with the function of forming the liquid phase and agglomerating the particulate solid lubricant, during the sintering of the metallurgical composition conformed by compaction, presenting an average particle size smaller than about 45 μm.

A process for obtaining self-lubricating sintered products from a metallurgical composition of particulate materials, the process comprising:

• mixing, in predetermined quantities, particulate materials which define the metallurgical composition;
• homogenizing the particulate material mixture;
• compacting the particulate material mixture, so as to provide the mixture with the shape of the product to be sintered;
• and
• sintering the compacted and conformed mixture, at temperatures from about 1125° C. to about 1250° C., forming, during the sintering, a liquid phase with the particulate alloy element and thus promoting the agglomeration of the particulate solid lubricant in discrete particles dispersed in the volume of a structural matrix;
• wherein the metallurgical composition of particulate materials comprises,
• a main particulate metallic material, in the form of a main chemical element, wherein the main particulate metallic material is nickel, and at least one particulate hardening element, which form the structural matrix in the composite product to be sintered;
• a non-metallic particulate solid lubricant, wherein the particulate solid lubricant is selected from graphite, hexagonal boron nitride or from a mixture of both in any proportion;
• and
• at least one particulate alloy element capable of forming, during the sintering of the conformed metallurgical composition, a liquid phase between the main particulate metallic material which forms the structural matrix and the particulate solid lubricant, agglomerating the particulate solid lubricant in discrete particles, wherein the particulate hardening element, with the function of hardening the nickel matrix, and the particulate alloy element, with the function of forming the liquid phase and agglomerating the solid lubricant in discrete particles, are a mixture consisting of silicon, phosphorus and chrome, at contents from 2% to 8% by weight of the metallurgical composition.