Material with high resistance to wear

Abstract

Material and method for the production of material with isotropic, mechanical properties and improved wear resistance and high hardness potential. Method includes producing in a powder metallurgical (PM) method a slug or ingot from a material of ledeburite tool steel alloy, and subjecting one of the slug or ingot or a semi-finished product produced from the slug or ingot to full annealing at a temperature of over 1100 C., but at least 10 C. below the fusing temperature of the lowest melting structure phase with a duration of over 12 hrs. In this manner, an average carbide phase size of the material is increased by at least 65%, a surface shape of the material is rounded and a matrix is homogenized. Method further includes subsequently processing the material into thermally tempered tools with high wear resistance occurs or into parts to which abrasive stress is applied.

Claims

1. A method for the production of materials with isotropic mechanical properties and improved wear resistance and high hardness potential, comprising: producing in a powder metallurgical method a slug or ingot from a material of ledeburite tool steel alloy; subjecting one of the slug or ingot or a semi-finished product produced from the slug or ingot to a temperature treatment comprising a full annealing at a temperature of over 1100 C. but no higher than 1180 C. for a duration of over 12 hours but no longer than 24 hours, and subsequently, processing the material into thermally tempered tools with high wear resistance or into parts to which abrasive stress is applied, wherein a tool steel alloy has a chemical composition in percent by weight of: TABLE-US-00010 carbon 1.0 to 3.0 chromium up to 12.0 molybdenum 0.1 to 5.0 vanadium 0.8 to 10.5 tungsten 0.1 to 3.0 and Si, Mn, S, or N and impurities and balance iron, and is devoid of Ni, Al, Nb and Ti.

2. The method according to claim 1, wherein the powder metallurgical method comprises: nozzle atomizing a liquid metal alloy into a powder of the alloy using nitrogen; and hot isostatic pressing of the alloy powder, wherein the slug or ingot is a hot isostatic pressing slug or ingot.

3. The method according to claim 1, wherein a carbon content of the matrix is set to 0.45 wt % to 0.75 wt % and an average carbide phase diameter in the matrix is set to greater than 2.8 microns.

4. The method according to claim 1, wherein the average carbide phase diameter in the matrix is set to greater than 3.2 microns.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

(2) Tab. 1 shows the chemical composition of tested materials;

(3) Tab. 2 shows the chemical composition of the matrix of the comparison alloy and of the material according to the invention (S599PM-H);

(4) FIG. 1 shows mechanical properties of the materials;

(5) FIG. 2 shows carbide phases in the PM material (S599PM) produced according to the prior art (SEM analysis);

(6) FIG. 3 shows carbide phases in the PM material (S599PM-H) produced according to the invention (SEM analysis);

(7) FIG. 4 shows carbide phases in the material according to the invention (S599PM-H) (SEM analysis);

(8) FIG. 5 shows the M.sub.6C phase from FIG. 4;

(9) FIG. 6 shows the MC phase from FIG. 4;

(10) FIG. 7 shows a phase image of a PM material (S599PM) according to the prior art, tempered;

(11) FIG. 8 shows a phase image of a PM material (S599PM-H) produced according to the invention, tempered;

(12) FIG. 9 shows a phase image of a cast and deformed material (S500);

(13) FIG. 10 shows a device for testing the wear performance (schematic).

DETAILED DESCRIPTION OF THE EMBODIMENTS

(14) The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

(15) The micrographs shown in FIGS. 3 and 4 result from scanning electron microscope (SEM) analyses using a scanning electron microscope SEM model: JEOL JSM 6490 HV, and the micrographs shown in FIGS. 5 and 6 result from using scanning electron microscope EDX model: Oxford Instrument sinca-Pentafet x3 Si (Li) 30 mm.sup.2.

(16) The M.sub.6C and MC carbide phases were created by carbide phase selection using the image processing software: Image J.

(17) From Tab. 1, the chemical composition of a standard alloy (AISI type M42) with the designation S500 and that of a powder metallurgically produced material S599PM as well as that of a material S599PM-H (see Tab. 2) according to embodiments of the invention can be recognized.

(18) The material with the designation S500 served as a comparison material of typical manufacture, because this has good wear properties according to the prior art.

(19) The alloy corresponding to the composition designated as S599 was smelted, and an HIP ingot was produced from this according to the PM method, turning the molten mass into powder by nozzle atomization using nitrogenfilling a capsule with this powder and hot isostatic pressing of the capsule.

(20) One part of this HIP ingot was processed in a customary manner into samples and tools with the designation S599-PM.

(21) On the second part of the ingot material from the same molten mass, a full annealing according to embodiments of the invention occurred on the semi-finished product with a square cross section of 100 mm at 1180 C. with a duration of 24 hours, and a subsequent further processing of the material with the designation S599PM-H occurred.

(22) Tab. 2 illustrates the chemical composition of the matrix and the portions of carbide phases in the comparison material S500 and in the material S599PM-H produced according to embodiments of the invention.

(23) In FIG. 1, the mechanical properties, such as elongation limit R.sub.P0.2, tensile strength Rm, elongation at fracture A and area reduction at fracture Z, of the materials 5500, S599PM and S599PM-H are shown in a bar graph.

(24) As a result of the full annealing according to embodiments of the invention, the elongation A and the area reduction Z of the material S599PM-H are clearly increased, which is caused by a homogenization of the matrix.

(25) FIG. 2 shows in micrograph a material S599PM in the soft-annealed state with carbide phases of the type M.sub.6C and MC in the matrix. The phase size of the carbides is on average approx. 2.0 M.

(26) The fine M.sub.23C.sub.6 carbides are not included in the evaluation of the material with a hardness of approx. 258 HB.

(27) FIG. 3 shows in micrograph the material S599PM-H, which was produced according to the embodiments of invention. At identical carbide phase proportions, the carbides are significantly coarsened and have an average diameter of approx. 4.0 m.

(28) In the matrix with a hardness of approx. 254 HB, fine M.sub.23C.sub.6 carbides are again intercalated because the material is present in the soft-annealed state.

(29) FIG. 4 shows a material S599PM-H produced according to embodiments of the invention in an SEM analysis (scanning electron microscope), which is tempered to a hardness of 68.7 HRC.

(30) With respect to FIG. 4 and FIG. 5, it should also be noted that the M.sub.23C.sub.6 carbides no longer appear in the image after a tempering.

(31) In FIG. 5, the carbide phases of the type M.sub.6C, selected using an aforementioned image program, can be seen.

(32) The M.sub.6C carbide phase proportion is approx. 7.4 percent by volume, wherein this value resulted from more than 6 measurements as a mean value.

(33) In FIG. 6, the carbide phases of the type MC are illustrated from the testing of the tempered material with a proportion of approx. 1.8 percent by volume, wherein the mean value was likewise calculated from more than 6 measurements.

(34) FIG. 7 shows in a micrograph (polished, solvent-etched using 3% HNO3) a powder metallurgically produced material S599 PM in the thermally tempered state having a homogenous distribution of the fine carbides with a medium carbide phase size of 1.6 m. The material hardness is approx. 68.2 HRC.

(35) In FIG. 8, the same material, which is tempered using identical parameters, which however was subjected to a full annealing according to embodiments of the invention, is shown in micrograph. The measurements of the medium carbide phase size yielded a value of 3.6 m.

(36) FIG. 9 shows the structure of a material S500 produced using a cast ingot in micrograph in the annealed state with a hardness of 239 HB. The material has angular, coarser carbide phases arranged slightly bandwise.

(37) Tests concerning the wear performance of the materials occurred by a device which is illustrated schematically in FIG. 10.

(38) In the abrasion wear test, samples on a disc which had a diameter of 300 mm and was fitted with SiC abrasive paper P120 were pressed on using a contact force per sample of 13.33 N, which corresponded to a surface pressure of 0.265 N/mm.sup.2. The rotation speed of the disc was 150 and 300 min.sup.1.

(39) The results of the abrasion wear test of tempered samples from respectively 12 tests were valued at 100% for the comparison material 5500.

(40) The powder metallurgically produced tempered material S599PM of the same type with fine carbide phases exhibited by comparison a wear rate of approx. 98%.

(41) The tests of the material S599PM-H, which was treated according to embodiments of the invention using full annealing during production and produced under the same tempering parameters, exhibited an increase in wear resistance of 33% to approx. 130% of the value of S500 and S599PM.

(42) It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.