Hard phase forming alloy powder, wear resistant sintered alloy, and production method for wear resistant sintered alloy

a technology production method, which is applied in the field of hard phase forming alloy powder, production method can solve the problems of increased cost of wear resistant sintered alloy, increased cost of co—mo—si alloy, etc., and achieves higher corrosion resistance, lower cost, and high corrosion resistance.

Inactive Publication Date: 2010-01-14
HITACHI POWDERED METALS COMPANY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007]In the hard phase forming alloy powder of the present invention, Cr, which is relatively low cost, is used as a matrix strengthening element. Cr is added to a raw powder of a wear resistant sintered alloy and is sintered, whereby Cr forms a hard phase dispersed in the sintered alloy. In sintering, Cr in the hard phase forming alloy powder strengthens the alloy matrix of the hard phase, and Cr is dispersed from the hard phase forming alloy powder and strengthens the iron-based alloy matrix of the wear resistant sintered alloy. In addition, Cr forms a passive oxide film on the surface of a wear resistant part. Therefore, a wear resistant sintered alloy using the hard phase forming alloy powder of the present invention exhibits superior corrosion resistance and wear resistance.
[0022]In the hard phase forming alloy powder of the present invention, Cr, which is relatively low cost, is used as a matrix strengthening element. Cr is added to the raw powder of a wear resistant sintered alloy and is sintered, whereby Cr forms a hard phase dispersed in the sintered alloy. In sintering, Cr in the hard phase forming alloy powder strengthens the alloy matrix of the hard phase, and Cr is dispersed from the hard phase forming alloy powder and strengthens the iron based alloy matrix of the wear resistant sintered alloy. In addition, Cr forms a passive oxide film on the surface of a wear resistant part. Therefore, the wear resistant sintered alloy using the hard phase forming alloy powder of the present invention exhibits superior corrosion resistance and wear resistance. Accordingly, the wear resistant sintered alloy of the present invention is preferably used for valve sheets of internal-combustion engines using an alcohol fuel as a fuel.

Problems solved by technology

The cost of a wear resistant sintered alloy, in which Co—Mo—Si alloy is dispersed as a hard phase, has increased because the costs of Co and Mo have been rising recently.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example a

Hard Phase Forming Alloy Powder

Example A-1

[0072]An iron powder, a copper powder, a graphite powder, and a hard phase forming alloy powder having a composition shown in Table A-1 were prepared. The iron powder, 1.5% of the copper powder, 35% of the hard phase forming alloy powder, and 1% of the graphite powder were added and mixed with a forming lubricant (0.8% of zinc stearate), and a raw powder was obtained. The obtained raw powder was compacted at a compacting pressure of 650 MPa so as to be formed in a ring shape with an outer diameter of 30 mm, an inner diameter of 20 mm, and a height of 10 mm. Next, these green compacts were sintered at 1160° C. for 60 minutes in a decomposed ammonia gas atmosphere, and samples Nos. A01 to A07 were formed. Simple wear tests and corrosion tests were performed on these samples. The results of these tests are shown in Table A-1.

[0073]The simple wear tests were performed with the input of colliding and sliding under high temperature. Specifically,...

example a-2

[0076]The iron powder, the copper powder, the graphite powder used in the example A-1, and a hard phase forming alloy powder having a composition shown in Table A-2 were added and mixed in the same ratio as in the example A-1, and a raw powder was obtained. The obtained raw powder was compacted and sintered in the same way as in the example A-1, and samples Nos. A08 to A13 were formed. The wear tests were performed in the same way as in the example A-1 for these samples. The results and the values of the samples Nos. A01 and A05 are shown in Table A-2.

TABLE A-2Compositions ofhard phase formingWear amountalloy powderSubstitutionalμmSamplemass %ratioValveNo.CoFeCrMoSiof FesheetValveTotalNotesA01Balance—8.0028.002.50—45348Conventional exampleA08Balance—30.0020.003.00—25328Practical exampleA09Balance 7.0030.0020.003.001530333Practical exampleA05Balance17.0030.0020.003.003635338Practical exampleA10Balance28.2030.0020.003.006037340Practical exampleA11Balance37.6030.0020.003.008045449Compa...

example a-3

[0078]The iron powder, the copper powder, the graphite powder used in the example A-1, and a hard phase forming alloy powder having a composition shown in Table A-3 were added and mixed in the same ratio as in the example A-1, and a raw powder was obtained. The obtained raw powder was compacted and sintered in the same way as in the example A-1, and samples Nos. A14 to A17 were formed. The wear tests were performed in the same way as in the example A-1 for these samples. The results and the values of the samples Nos. A01 and A05 are shown in Table A-3.

TABLE A-3Compositions ofhard phase formingWear amountalloy powderSubstitutionalμmSamplemass %ratioValveNo.CoFeCrMoSiof FesheetValveTotalNotesA01Balance—8.0028.002.500.045348Conventional exampleA05Balance17.0030.0020.003.0036.235338Practical exampleA14Balance17.0030.0020.003.0036.232335Practical exampleA15Balance17.0030.0020.003.0036.227431Practical exampleA16Balance17.0030.0020.003.0036.2351247Practical exampleA17Balance17.0030.0020.00...

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PUM

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Abstract

A hard phase forming alloy powder, for forming a hard phase dispersed in a sintered alloy, consists of, by mass %, 15 to 35% of Mo, 1 to 10% of Si, 10 to 40% of Cr, and the balance of Co and inevitable impurities. A production method, for a wear resistant sintered alloy, includes preparing a matrix forming powder, the hard phase forming alloy powder, and a graphite powder. The production method further includes mixing 15 to 45% of the hard phase forming alloy powder and 0.5 to 1.5% of the graphite powder with the matrix forming powder into a raw powder. The production method further includes compacting the raw powder into a green compact having a predetermined shape and includes sintering the green compact. A wear resistant sintered alloy exhibits a metallic structure in which 15 to 45% of a hard phase is dispersed in a matrix. The hard phase consists of, by mass %, 15 to 35% of Mo, 1 to 10% of Si, 10 to 40% of Cr, and the balance of Co and inevitable impurities.

Description

BACKGROUND OF THE INVENTION[0001]1. Technical Field[0002]The present invention relates to a hard phase forming alloy powder that may preferably be used for forming a hard phase dispersed in a wear resistant sintered alloy. The wear resistant sintered alloy, such as that used in valve sheets for internal-combustion engines, must have wear resistance at high temperatures. The present invention also relates to a production method for a wear resistant sintered alloy using the hard phase forming alloy powder, and the wear resistant sintered alloy may preferably be used for valve sheets for internal-combustion engines. In addition, the present invention relates to a wear resistant sintered alloy obtained by the production method.[0003]2. Background Art[0004]For a sintered alloy, the alloy design can be freely selected, and various characteristics, such as heat resistance and wear resistance, can be easily added thereto compared to doing so for ingot materials. Therefore, the sintered allo...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B22F3/12C22C19/07C22C30/00
CPCB22F2998/10C22C33/0285C22C38/52C22C38/46C22C38/48C22C38/02C22C38/44B22F3/02B22F3/10C22C19/07C22C1/04
Inventor KAWATA, HIDEAKI
Owner HITACHI POWDERED METALS COMPANY
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