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

Patent metadata

Field	Value
Publication number	US-10835957-B2
Application number	US-201816145658-A
Country	US
Kind code	B2
Filing date	Sep 28, 2018
Priority date	Sep 12, 2008
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

The metallurgical composition comprises a main particulate metallic material, for example iron or nickel, and at least one alloy element for hardening the main metallic material, which form a structural matrix; a particulate solid lubricant, such as graphite, hexagonal boron nitride or mixture thereof; and a particulate alloy element which is capable of forming, during the sintering of the composition conformed by compaction or by injection molding, a liquid phase, agglomerating the solid lubricant in discrete particles. The composition may comprise an alloy component to stabilize the alpha-iron matrix phase, during the sintering, in order to prevent the graphite solid lubricant from being solubilized in the iron. The invention further refers to the process for obtaining a self-lubricating sintered product.

First claim

The invention claimed is:

1. 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 a 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;
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 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 an 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.

2. The process, as set forth in claim 1 , further comprising:
stabilizing the 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 iron structural matrix.

3. The process, as set forth in claim 1 , wherein the step of compacting the particulate material mixture, which defines the metallurgical composition, comprises rolling the latter in the form of a plate or strip to be subsequently sintered.

4. The process, as set forth in claim 1 , wherein the step of compacting the particulate material mixture, which defines the metallurgical composition, comprises rolling the latter on at least one of the opposite faces of a structural substrate in the form of a plate or strip of particulate material compatible with the main particulate metallic material which forms the structural matrix.

5. The process, as set forth in claim 3 , further comprising, after sintering the particulate materials, the additional step of cold rolling the plate or strip for reducing the residual porosity.

6. The process, as set forth in claim 1 , wherein the step of compacting the particulate material mixture, which defines the metallurgical composition, comprises the extrusion in one of the shapes defined by a bar and a tube.

7. The process, as set forth in claim 1 , wherein the step of compacting the particulate material mixture, which defines the metallurgical composition, comprises the co-extrusion of the latter in the form of a surface layer around a structural core in the form of a bar of particulate material compatible with the main particulate metallic material which forms the structural matrix, so as to form a composite bar.

8. The process, as set forth in claim 1 , wherein the metallurgical composition comprises an organic binder to be thermally removed from the product, before the sintering step.

9. 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.

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

Assignees

• Whirlpool Sa
• Univ Federal De Santa Catarina Ufsc
• Lupatech S A
• Embraco Ind De Compressores E Solucoes Em Refrigeracao Ltda

Inventors

• Binder Roberto
• Klein Aloisio Nelmo
• Binder Cristiano
• Hammes Gisele
• Parucker Moises Luiz
• Ristow Junior Waldyr

Classifications

• B22F1/105

  containing inorganic lubricating or binding agents, e.g. metal salts · CPC title

• B22F1/00

  Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties · CPC title

• C22C33/02

  by powder metallurgy · CPC title

• B22F3/10

  Sintering only · CPC title

• B22F7/08 Primary

  with one or more parts not made from powder {(B22F7/062 takes precedence)} · CPC title