Powdered Metallurgy (PM) is a well developed manufacturing process for producing precision metal parts. The technology has being commercially used for producing components for over seven decades.

Made by mixing elemental or alloy powders and compacting the mixture in a die, the resultant shapes are then sintered or heated in a controlled atmosphere furnace to bond the particles metallurgically. Basically a net shape metal working process, PM typically uses more than 97% of the starting raw material in the finished product. Through this, PM conserves energy and material.

The PM process is cost effective in producing simple or complex parts at or very close to final dimensions requiring very little or no further machining operations in most of the cases. The production rates normally range from few hundreds to thousands per hour.

PM parts need no machining or very little machining before they can be used. They can be sized for closer dimensional control. In some cases PM parts are re-pressed for higher density and strength.

PM parts can be subjected to most of the varieties of heat treatment used on wrought material. They can be plated, welded & brazed. Normally they are resin impregnated to close the pores before plating.

Due to inherent porosity, PM parts can hold lubricating medium like oil and graphite in their pores. PM bearings are normally 'fit & forget' as they hold oil for life time.

Porosity in the PM parts can also be closed through steam treatment process. Steam treatment closes the interconnected porosity in the part while enhancing material strength and hardness significantly. Steam treatment leaves a fine layer of passive ferrous oxide, which provides corrosion resistance.

Most of the PM parts weigh less than 5 pounds although parts weighing as much as 35 pounds can be fabricated on conventional PM equipment. Many of the early PM parts, such as bushings and bearings, were simple shapes, as compared with the complex contours and multiple levels which are economically produced today.

PM Applications

The basic versatility of PM is applied in numerous industries, including automotive, business machines, aerospace, electrical and electronic equipments, home appliances, lawn and farm equipments, sporting goods, hand & power tools etc. Thousands of different cost-saving, reliable PM designs now serve these industries in a wide range of engineering applications which fall into two main groups. In one group are parts which are very difficult to make by any other production method. For example, parts of difficult -to-fabricate material such as tungsten and molybdenum, or tungsten carbide, can not be made efficiently by any other process. Also porous bearings, filters and many hard and soft magnetic parts are exclusively products of the PM process.

Another, and larger application group consists of components where PM is an effective alternative to machined parts, Casting, Forging & Fine Blanking. PM technology has also expanded into precision hot forging from sintered performs, thus extending it's capabilities to providing PM parts with increased strength, toughness and fatigue life.

PM Materials

As precision engineered materials, a diverse group of metal powders is available for a wide range of PM products. Generally, powder mixes for compacting are prepared from three powder types.

The first is a admixed , where elemental alloying powders such as copper, nickel, graphite and tin are added to the base elemental powders such as iron and copper.

Partially alloyed powder is composed of two or more elements where the alloying additives are diffusion bonded to the base powder during the powder manufacturing process. These powders produce a near homogeneous microstructure with good dimensional control and excellent as-sintered mechanical properties.

Pre-alloyed powders, on the other hand are atomized from alloyed furnace melts; each powder particle has the same nominal composition throughout. Pre-alloyed powders yield homogeneous phase constituents in the micro-structure.

You may choose the appropriate PM material from a few widely accepted international standards like the following