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Corrosion resistant metallurgical powder compositions, methods, and compacted articles

a technology of corrosion resistance and metallurgical powder, which is applied in the field of corrosion resistant metallurgical powder compositions and compacted articles, can solve the problems of insufficient improvement, inability to achieve high strength applications of some stainless steels, and increase the cost of preparing compacted articles. achieve high fatigue endurance limits, maintain ductility, and high strength

Inactive Publication Date: 2006-12-21
HOEGANNES
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007] Provided are corrosion resistant metallurgical powder compositions, corrosion resistant compacted articles prepared from metallurgical powder compositions, and methods of preparing the same. Corrosion resistant metallurgical powder compositions include as a major component, an iron-based powder and, as a minor component, alloy additives that include chromium, and carbon. Upon compaction and sintering, the iron-based powder and alloy additives form a dual phase alloy system. The dual phase alloy system is characterized by an admixed martensite and ferrite microstructure. This unique microstructure results in beneficial physical properties, such as for example, high strength, hardness, and ductility, impact energy, and fatigue endurance, while maintaining resistance to corrosion.
[0008] Corrosion resistant metallurgical powder compositions are low cost alternatives to conventional alloys, which require high alloy content or secondary processing steps, e.g., heat treatments, to provide sufficient strength. Thus, corrosion resistant metallurgical powder compositions are an improved high-strength, corrosion-resistant stainless steel product as compared with presently-existing compositions having similar chromium levels.
[0011] Methods of preparing compacted articles include the steps of providing a corrosion resistant metallurgical powder composition, and compacting the composition to form a green compact. Then, the green compact is sintered to form the dual phase microstructure. Upon sintering, the present compositions provide unusually high strength and high fatigue endurance limits while maintaining ductility and high impact strength.

Problems solved by technology

However, the strength of some stainless steels generally can not be improved without increasing the alloy content of a composition or utilizing secondary processing techniques, both of which increase the cost of preparing compacted articles.
Although some improvement in strength is observed by increasing the alloy content of a compositions, the improvement is often insufficient to enable the use of some stainless steels in high strength applications.
Moreover, traditional secondary processing techniques utilized to increase strength are unavailable for certain stainless steels.

Method used

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  • Corrosion resistant metallurgical powder compositions, methods, and compacted articles
  • Corrosion resistant metallurgical powder compositions, methods, and compacted articles
  • Corrosion resistant metallurgical powder compositions, methods, and compacted articles

Examples

Experimental program
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Effect test

example 1

[0095] Corrosion resistant metallurgical powder compositions, identified as test compositions DP1 through DP5, were prepared and compared with commercially available stainless steel compositions. Test compositions DP1 through DP 5 were prealloyed iron based powders that included the alloying alements shown below in Table 1. The iron and alloy elements of each composition were melt blended and water atomized to provide corrosion resistant metallurgical powder compositions. The atomized powders were than admixed with 0.75 weight percent of lubricant, which was commercially available as Acrawax C, from Lonza Corporation. DP1 though DP5 had ferritic factors ranging from 6.1 to 14.2. These test compositions were compared to two conventional ferritic stainless steel powders, commercially available as 410L and 430L grade powders from Hoeganaes Corporation. The 410L powder was admixed with graphite powder prior to compaction and sintering to provide a higher martensitic microstructure.

TAB...

example 2

[0103] The mechanical and physical properties of corrosion resistant compacts were compared to conventional stainless steels typically used in high strength applications. A compacted article, DP6, was prepared according to the steps described above with the composition shown in Table 4 below. The conventional stainless steels tested were commercially available as 17-4PH, 409LNi, and 410L with graphite addition, each sold by Hoeganaes Corporation. The 17-4PH powder was a precipitation hardening, martensitic stainless steel that combines high strength and hardness with corrosion resistance. Upon compaction, articles prepared from this powder were age hardened prior to testing. The 409LNi powder is an admixture of conventional 409Cb powder commercially available from Hoeganaes Corporation and elemental nickel powder commercially available from Inco-123. 409Cb is typically used in conventional automotive exhaust flange applications. As described above, the 410L+graphite compositions, ha...

example 3

[0111] The corrosion resistance properties of the compacted parts from Example 2 were tested. Two types of corrosion tests were performed. The first corrosion test, a salt spray test, was performed on the compacts according to ASTM Standard B 117-03. Five test bars were tested per alloy. The percent area of the bars covered by red rust was recorded over time. The results are shown below in Table 8:

TABLE 8Red Rust After 24 Hours(%)DP65.00410L + graphite84.00409LNi20.0017-4PH1.0

[0112] As shown in Table 8, the high alloy content of the compact prepared from 17-4PH result in the lowest amount of rust after 24 hours, i.e., the highest resistance to corrosion. However, at lower chromium levels the compacts prepared with DP6 exhibited comparable resistance to corrosion. The corrosion resistance of the compact prepared from DP6 was superior to the corrosion resistance of the compacts prepared from 409LNi and 17-4PH respectively. Without being limited by theory it is believed that the addi...

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Abstract

Provided are corrosion resistant metallurgical powder compositions, corrosion resistant compacted articles prepared from metallurgical powder compositions, and methods of preparing the same. Corrosion resistant metallurgical powder compositions include as a major component, an iron-based powder and, as a minor component, alloy additives that include chromium, and carbon. Upon compaction and sintering, the iron-based powder and alloy additives form a dual phase alloy system. The dual phase alloy system is denoted by an admixed martensite and ferrite microstructure. This unique microstructure results in beneficial physical properties, such as for example, high strength, hardness, and ductility, impact energy, and fatigue endurance, while maintaining resistance to corrosion.

Description

[0001] This application claims the priority benefit of U.S. Provisional Application Ser. No. 60 / 692,387, filed Jun. 20, 2005, which is herein incorporated by reference in its entirety.FIELD OF THE INVENTION [0002] The present invention relates to metallurgical powder compositions, compacted articles prepared from metallurgical powder compositions, and methods of making the same. More particularly, the present invention is directed to corrosion resistant metallurgical powder compositions, corrosion resistant compacted articles prepared from metallurgical powder compositions, and methods of preparing the same. BACKGROUND OF THE INVENTION [0003] Iron-based particles have long been used as a base material in the manufacture of structural components by powder metallurgical techniques. These techniques involve first compacting iron-based particles in a die under high pressures in order to produce an article having a desired shape. After the compacting step, the structural component may un...

Claims

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Application Information

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IPC IPC(8): C22C38/18B22F3/12C22C33/02
CPCB22F2009/0828B22F2998/10B22F2999/00C22C33/0285C22C38/18B22F9/082B22F1/0059B22F3/02B22F3/10B22F2201/013
Inventor SCHADE, CHRISTOPHER T.
Owner HOEGANNES
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