Abstract: A method of making a sintered article is disclosed, the method comprising the steps of mixing a prealloyed ferrous powder having a composition in the following ranges in weight %: carbon 0.7-2.7/chromium 3-6/cobalt 5-10/vanadium 0.5-3/molybdenum 6-11/silicon 0.3-2/ others total 2 max/balance iron and optionally up to 3 wt % tungsten, with an addition of carbon powder of at least 0.1 wt %, compacting said powder mixture by uniaxial pressing to form a green compact of near net shape, sintering said green compact in a continuous gas atmosphere sintering furnace at a temperature in the range from 1130.degree. C. to 1250.degree. C. such that the final density of said sintered material is greater than 95% of the theoretical density as a result of the sintering operation alone.

Abstract: A two layer valve seat insert and a method for its manufacture is described. The method comprises the steps of preparing two powder mixtures; a first powder mixture for forming the valve seat face layer; a second powder mixture for forming the valve seat base layer; sequentially introducing a predetermined quantity of each of said first and said second powder mixtures into a powder compacting die and having an interface therebetween substantially perpendicular to the axis of said die; simultaneously compacting said first and said second powder mixtures to form a green compact having two layers and sintering said green compact, wherein at least one of the chemical composition or the physical characteristics of at least one of said first and said second powder mixtures is adjusted so as to result in said valve seat face layer and said valve seat base layer having substantially the same density after compaction.

Abstract: A method of making an article by joining together at least two porous components is described, the method comprising the steps of making at least two generally tubular PM components to be joined in the axial direction, each component having an axial length less than that of the tubular article; the at least two components both having interconnected porosity and each having at least one mutual mating face; assembling the at least two components together so that the at least one mutual mating faces are in proximity to each other; placing an infiltrant material in the bore of the assembled components; heating the assembled components to melt the infiltrant material and cause it to infiltrate the interconnected porosity at least in the region of the mutual mating faces so as to cause the components to become bonded together by the infiltrant material. Examples of the manufacture of valve guides are given.

Abstract: An aluminium alloy made by a powder metallurgy route and a method for its production are described. The method comprises the steps of producing a first powder of a near-eutectic aluminium-silicon based alloy; producing a second powder of a hypereutectic aluminium-silicon based alloy; mixing desired proportions of the two powders together; compacting the powder mixture and sintering the compacted powder.

Abstract: A method is described for the manufacture of a sintered ferrous-based material having improved machinability, the method comprises the steps of making a mixture of a ferrous-based powder, the mixture including a compound containing at least one metal from the group comprising manganese and the alkaline-earth series of metals; at least one sulphur donating material; pressing the powder mixture and sintering the pressed mixture so as to cause the formation by reaction during sintering of at least one stable metal sulphide within the sintered material. Materials and articles made by the method are also described.

Abstract: Sintered ferrous materials are described having a composition in wt % lying within the ranges of C 0.8-1.5/W 1-4.4/Mo 1-4.4/V 1-2.6/Cr 1.3-3.2/Others 3 max./Fe balance. The material may be made by a method comprising the steps of mixing between 40 and 70 wt % of a powder having a composition in wt % within the ranges C 0.45-1.05/W 2.7-6. 2/Mo 2.8-6.2/V 2.8-3.2/Cr 3.8-4.5/Others 3.0 max./Fe balance with between 60 and 30 wt % of an iron powder and from 0.4 to 0.9 wt % of carbon powder, pressing a green body of the article from the mixed powder and then sintering the green body. The material may optionally contain sulphur, metallic sulphides. The material may be infiltrated.

Abstract: Sintered materials and a method are described for the production of ferrous articles, particularly valve seat inserts. The materials are based on A1S1 H11, H12 and H13 materials plus diluent material.

Abstract: A valve guide and a method for the manufacture thereof are described. The valve guide is a tubular article having a length to outer diameter ratio greater than about 1.5 and is made of a ferrous material by a PM route. The pressed guide is infiltrated by preparing a sheet of the infiltrant alloy, rolling the sheet into a cylinder and inserting it into the guide bore followed preferably by, simultaneous sintering and infiltration.

Abstract: Sintered ferrous materials are described having a composition in wt % lying within the ranges of C 0.8-1.5/W 1-4.4/Mo 1-4.4/V 1-2.6/Cr 1.3-3.2/Others 3 max./Fe balance. The material may be made by a method comprising the steps of mixing between 40 and 70 wt % of a powder having a composition in wt % within the ranges C 0.45-1.05/W 2.7-6. 2/Mo 2.8-6.2/V 2.8-3.2/Cr 3.8-4.5/Others 3.0 max./Fe balance with between 60 and 30 wt % of an iron powder and from 0.4 to 0.9 wt % of carbon powder, pressing a green body of the article from the mixed powder and then sintering the green body. The material may optionally contain sulphur, metallic sulphides. The material may be infiltrated.

Abstract: A valve seat insert surrounds an inlet valve of a reciprocating internal combustion engine and provides a seat for a movable valve. The flow characteristics of a charge of air or an air/fuel mixture leaving the inlet valve are determined at least in part by the form of the valve seat insert and these characteristics can affect the performance of the internal combustion engine. The improved valve seat insert defines an aperture through which the charge passes. The aperture has an area to one side of a plane including the axis of an annular valve engaging surface of the insert which is greater than the area of the aperture to the other side of the plane. The smaller of the areas is bounded by one or more curved sections. This insert can be used in an internal combustion engine or deflect a charge passing through the aperture and to give the charge a velocity profile which, for example, improves starting and reduces fuel consumption.

Abstract: Sintered metal articles especially sealing rings of less than 25 mm diameter are formed by plating sintered metal skeletons with a metal of lower melting point than the metal of the skeletons, for example, copper. The plated skeletons are then heated, preferably in a stack, to melt the plated metal, which infiltrates the skeletons. The articles so produced are stronger than and have greater elasticity than the skeletons themselves due to the presence of the plated metal in the skeletons.

Abstract: The invention consists of a process for the production of articles by powder metallurgy including the step of adding powdered mica to the metal powder before compacting and sintering. It also extends to a sintered metal product containing mica, in particular a valve seat insert and a shock absorber piston ring. The quantity of mica is preferably between 0.5% and 2% by weight of the metal.

Abstract: A sintered metal article such as a piston ring or a sealing ring (in particular those having a cross-section area not exceeding 20 mm.sup.2) having a density which is at least 88.5% of the theoretical density, having a fine machined surface finish, and having a nitrocarburized surface layer which is not found at a depth of more than about 250 microns from the surface.The invention also includes the process of manufacturing such an article.

Abstract: A metal article is formed by a sintered body of an austenitic ferrous alloy containing chromium and nickel, the ferrous alloy having been infiltrated with a copper or copper base alloy during or after sintering of the body.When a body of aluminum or aluminum alloy is cast around the metal article, a good bond therebetween is achieved. The metal article can thus provide a wear-resistant insert, for example a piston ring carrier in an aluminum piston or a valve seat in an aluminum cylinder head for an automobile.