Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Making composite or hollow article
Patent
1997-08-06
2000-02-08
Jenkins, Daniel J.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Making composite or hollow article
419 10, 419 12, 419 13, 419 14, 419 19, 419 23, 419 48, 419 49, 419 38, B22F 312, B22F 702
Patent
active
060225084
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of powder metallurgical manufacturing of a composite material containing particles in a metal matrix, said composite material having a high wear resistance in combination with a high toughness.
BACKGROUND OF THE INVENTION
Wear resistant metal material conventionally consist of a solidified metal matrix in which hard particles such as borides, carbides, nitrides or intermetallic phases appear as inclusions. The wear resistance and the fracture toughness in such materials are usually highest when the hard particles are evenly dispersed in the metal matrix and when a net-like distribution is avoided. At a given amount of evenly dispersed hard particle the fracture strength of the material is reduced as the size of the hard particles is raised, while the fracture toughness is increased. This can be explained in the following way with reference to the accompanying FIGS. 1a and 1b. When the material is subjected to a tension or bending load, F, cracks are initially formed in the brittle hard particles, FIG. 1A. These cracks are the greater, the greater the hard particles are, and propagate already at a low tension to fracture; in other words the fracture strength decreases as the sizes of the hard particles are raised. At a given content of hard particles, however, the mean spacing between the hard particles increases with the sizes of the hard particles, FIG. 1b. Therefore, a plastic zone can be established in the metal matrix in front of a crack, avoiding further cracks in the hard particles, wherein the fracture toughness will increase in relation to the spacing between the hard particles. At a given content of hard particles and consequently at a given wear resistance, an improved fracture toughness is accompanied by an impaired fracture strength.
BRIEF DISCLOSURE OF THE INVENTION
It is the purpose of the present invention to provide a composite material containing particles in a metal matrix, wherein the material will have a high wear resistance in combination with a high fracture strength and fracture toughness. This can be achieved by a method defined in the characterizing part of the accompanying claim 1. Further characteristic features of the invention are disclosed in the subsequent claims and in the following description, wherein reference will be made to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1a and 1b schematically describe the relationship between the sizes of the hard particles and the mechanical properties fracture strength and fracture toughness for a dispersion structure at a given content of hard particles,
FIGS. 2a and 2b schematically illustrate a one step and a two step dispersion structure, respectively, at equal volume contents of hard particles,
FIG. 3 shows a two step dispersion structure made from a mixture of a first powder I and a second powder II, and
FIG. 4 is a graph diagram of the ratio between the mean diameters of a first and a second powder versus the volume content of the first powder I.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, the well-known dispersion structure of FIG. 2a, which is obtained by a one step procedure, wherein the hard particles HT in a metal matrix MM is replaced by the dispersed structure achieved by a two step procedure, FIG. 2b. The two step dispersion structure of the invention, FIG. 2b, contains regions with a dense dispersion of fine, hard particles in a first metal matrix MM I, wherein these regions which are rich of fine, hard particles in their turn appear as a dispersion of inclusions in a second metal matrix MM II, which is essentially lacking hard particles. The two step dispersion micro structure of the invention has a high fracture strength because of its small hard particle diameters in the first metal matrix MM I and also a high fracture toughness because of the large spacing between the hard particles in the second matrix MM II.
In the following, the advantages of the micro structure obtained by the two step dispersion in
REFERENCES:
patent: 5723799 (1998-03-01), Murayama et al.
patent: 5835841 (1998-11-01), Yamada et al.
Patent Abstracts of Japan, vol. 10, No. 323, M-531, Abstract of JP, A, 61-130404 (Toyota Central Res & Dev Lab Inc.), Jun. 18, 1986 Patent Abstracts of Japan, vol. 8, No. 52, C-213, Abstract of JP, A, 58-207340 (Sumitomo Denki Kogyo K.K.), Dec. 2, 1983.
Int'l Journal of Refractory & Hard Metals, vol. 6, No. 3, Sep. 1987, (Quebec, Canada), Champagne B., "Properties of WC-Co/Steel Composites", pp. 155-160, see p. 155, col. 1, line 24-p. 156, col. 2, line 15; p. 157, col. 1, line 7--col. 1, line 28, p. 159, col. 1, p. 7--p. 160, col. 2, p. 31.
Erasteel Kloster Aktiebolag, Sweden
Jenkins Daniel J.
Koppern GmbH & Co., KG, Germany
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