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Copper steels are used to fabricate high strength parts. The alloys are useful because they exhibit high strength, hardness and wear resistance. Copper alloy contents of 2-w/o are most popular. Higher copper content is alloyed to increase wear resistance. In the as-sintered condition, these alloys achieve ductility of less than 1%. Of alloys containing from 2-w/o to 10-w/o copper with 0.45 or 0.8-w/o combined carbon, specimens were compacted at 425 or 640 MPa, and sintered using a cycle commonly applied in a belt furnace. The alloys were found to have combined carbon content within controllable limits. Contamination was low. The tensile strength of the sintered copper steel was higher than that of typical values listed in Standard 35. Elongation for 2-w/o-copper/9-w/o-carbon copper steels was 3%. For 5-w/o-copper/9-w/o-carbon copper steels, elongation was 2%. Processing and cost to obtain these properties is discussed. Additional work now in progress will also be discussed.

Often the question has been posed as to where are markets for P/M stainless steels. This question has been difficult to answer. Stainless steels are more expensive than alloy steels, because they contain chromium to provide corrosion resistance. Chromium poses a problem for P/M parts fabricators. Many sinter parts at 2050°F (1120°C). Furthermore, most insist on including at least 25% nitrogen in the sintering atmosphere. If 2050°F (1120°C) is selected for sintering, surface oxides are often only partially reduced. In addition, if nitrogen dilutes the sintering atmosphere, nitriding occurs, limiting corrosion resistance. Therefore a limited market exists for P/M stainless steels because corrosion resistance is limited. However, there is a substantial market for stainless steel bar stock. One such market, totally undeveloped, is for parts for soft magnetic applications.

In the mid 1970's two developments made P/M technology applicable to magnetic applications. One was the development of a high purity, high compressibility water atomized powder. The second was the development of pure Fe2P or Fe3P powder to admix with iron powder to yield phosphorus iron P/M parts. Considerable work has been accomplished to produce quality P/M phosphorus irons to compete with traditional materials for magnetic applications. Owing to improvements in powders and sintering techniques, former predictor equations no longer apply, or their precision has been significantly improved, mainly as a result of very low interstitial contents. This report describes these recent developments and briefly discusses emerging problems.

An alternative process or material that exhibited excellent magnetic properties and corrosion resistance after submersion in a 5% salt solution for 1000 hours was introduced. Additional work has indicated this material can be an alternative to prealloyed ferritic stainless steels. Although prealloyed ferritic stainless steels exhibit magnetic properties comparable to wrought alloys, corrosion resistance has been less than desirable. Most prealloyed stainless steels do not sustain 100 hours in a 5% salt solution. This paper describes a mixture of elemental iron powder with 10 micron chromium powder to formulate an alloy of 430 composition upon sintering. Conditions for compacting the elemental mixture are compared with prealloyed 434L powder. Green properties, magnetic properties, and corrosion resistance related to compaction pressure, with an interpretation of results, are provided.

To date the market for P/M stainless steel has not developed appreciably, and has centered largely on the development of austenitic 300 series stainless steels. Although these stainless steels are noted for their resistance to corrosion in many media, it has been difficult for P/M parts fabricators to produce parts that will sustain 1,000 hours of protection in a 5% salt solution. The problem starts with the water atomized powders and continues with the sintering practice exercised to produce the parts. Reasons for lack of corrosion resistance, based upon these considerations, will be discussed. In addition, the ferritic stainless steels are being considered seriously for fuel injectors. These emerging applications derive from the corrosive environment that may become a problem if and when alternative fuels are introduced. P/M ferritic stainless steels may also assume a position as a corrosion resistant magnetic material required in ABS systems which are currently emerging.