National Research Council of Canada

Sylvain Pelletier

Yannig Thomas

Louis-Philippe Lefebvre

Blaise Champagne

Claude Gelinas

Abdelouahab Ziani

Sylvain St-Laurent

Kenneth C Cole

Linda Tremblay

Paul-Emile Mongeon

Near-net-shape soft magnetic components can be produced from iron powder-lubricant compositions using powder metallurgy techniques. The resulting components have isotropic magnetic and thermal properties and may be shaped into complex geometry using conventional compaction techniques. A non-coated ferromagnetic powder is mixed with a lubricant and compacted. After compaction, the components are thermally treated at a moderate temperature to burn out the lubricant, and possibly also relieve the stresses induced during pressing and reduce the hysteresis losses. Depending on the application, the properties of the material may be tailored by varying the content and type of the lubricant and the thermal treatment conditions.

Manufacturing soft magnetic components using a ferrous powder and a lubricant

Near-net-shape soft magnetic components can be produced from iron powder lubricant compositions using powder metallurgy techniques. The resulting components have isotropic magnetic and thermal properties and may be shaped into complex geometry using conventional compaction techniques. A non-coated ferromagnetic powder is mixed with a lubricant and compacted. After compaction, the components are thermally treated at a moderate temperature to burn out the lubricant, relieve the stresses induced during pressing and reduce the hysteresis losses. Depending on the application, the properties of the material may be tailored by varying the content and type of the lubricant and the thermal treatment conditions.

A method of lubricating the wall surfaces of a die cavity used in powder metallurgy involves spraying the wall surfaces with tribocharged particles of a lubricant material. The method is carried out by means of an apparatus centered about a plug member which has a three-dimensional shape conforming generally to that of the article to be formed. The plug member is slightly smaller than the article so that when the plug member is inserted into the die cavity there is a small, but uniform, gap created between the outer wall surfaces of the plug member and the walls of the die cavity. The plug member is secured to a closing plate which can be inserted into the die cavity so as to be sealed therewith. The closing plate is provided with vent holes and the plug member has a plurality of spaced apart tubes extending therethrough, which tubes exit at one or more of the wall surfaces of the plug member. The lubricant material is fed using an inert gas under pressure through tubing which tribocharged the lubricant particles and the tribocharged particles are sprayed from the tubes in the plug member into the gap so that they are electrostatically attracted to the walls of the die cavity and adhere thereto. Any excess gas and lubricant exits the gap through the vent holes in the closing plate. A uniform thin coating of lubricant is created on the walls of the die cavity. The green density of the article formed in the die is greater, and the ejection force required to remove the formed article from the die cavity is less, than with existing methods and apparatus.

Die wall lubrication method and apparatus

Metal powder compositions for powder metallurgy (P/M) applications contain a high-density polyethylene as a lubricant. The compositions are suitable for either cold or warm compaction. When compacted, the compositions yield parts having relatively high density, high green strength and good surface finish.

Lubricated ferrous powder compositions for cold and warm pressing

Post-compaction treatments of iron compacts to improve the mechanical strength of the compacts are provided. Powder is compacted into the desired part. The part is then subjected to a strengthening operation. This operation involves a heat treatment at a moderate temperature combined with an optional resin impregnation. The heat treatment is done at a temperature sufficient to increase the mechanical properties of the compact while maintaining the magnetic losses low for the required application. Impregnation with an insulating binder can be effected to increase the mechanical strength of the part without creating electric contacts between the powder particles.

Treatment of iron powder compacts, especially for magnetic applications

Complexable polymeric binder-lubricant blends are disclosed for production by powder metallurgy techniques of ferrous compositions with remarkably high green strength upon compaction, or soft magnetic ferrous powder/resin composites with improved processability and magnetic properties. An exemplary composition consists of a ferrous powder, a thermoset phenolic resin and poly(ethylene oxide), both polymers exhibiting, when intimately mixed, strong intermolecular acid-base interactions giving rise to an interpolymer complex which imparts a high strength to the resulting ferrous powder compact.

Ferrous powder compositions containing a polymeric binder-lubricant blend

The present invention relates to particle agglomeration of aluminum powder using a lubricating binder. The resulting powder has improved flowability and can be shaped easily. The aluminum particles are admixed with a lubricant, e.g. polyethylene, and are held together by the lubricant. To agglomerate the aluminum powder, the lubricant is melted and is then solidified to form solid bridges between the aluminum powder particles. The lubricant may be burned out cleanly at temperatures lower than 450.degree. C.

Lubricated aluminum powder agglomerates having improved flowability

This invention relates to a method for producing sintered parts of aluminum or aluminum alloy with improved mechanical properties using batch degassing, die compaction and liquid phase sintering. The batch degassing consists of holding a prealloyed aluminum powder at a temperature of about 350.degree. to about 450.degree. C. in a stainless steel autoclave in which the pressure is reduced to less than 5.times.10.sup.-6 torr. Once the desired pressure is reached the powder is cooled down within the autoclave while still under vacuum. The resulting powder is then compacted at a pressure of 20 to 50 tsi at between room temperature and about 250.degree. C., but preferably at a warm temperature of about 65.degree. C. The final densification is completed by liquid phase sintering in argon atmosphere at 625.degree. C. This method allows the production of sintered compacts characterized by a density close to 97% of theoretical, which makes it possible to eliminate the need for a hot working step.

Method for producing aluminum alloy powder compacts

A method for producing composite insulating coatings on powder particles, the coatings containing an electrically insulating metal compound and an organic polymer. The coatings are deposited preferably by controlled spraying, simultaneous or sequential, of sol precursors of insulating metal compounds and polymer emulsions or solutions onto polymer, metal or ceramic powder particles preferably during the blending or mixing of the particles. The process is useful for mass production of coated iron-based powders used for shaping components by powder metallurgy techniques for magnetic applications. Coated iron based powders can be cold or warm pressed and heat treated to obtain the desired mechanical properties.

Composite insulating coatings for powders, especially for magnetic

A novel high-performance binder system is provided for the fabrication of segregation-free iron based powder blends. The blends are prepared by using a binder system comprising thermoplastic resin polyvinylpyrrolidone and a suitable compatible plasticizer such as polyethylene glycol, and optional solid lubricants. The binder system enables the manufacture of segregation-free iron-based powder blends with high flow rate and compressibility, enhanced apparent density, green strength and transverse rupture strength, and low dimensional variations compared to unbonded powder blends and to blends made with PVP or PEG only as the binder.

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Sylvain Pelletier