Powdered Metal 101

What is powdered metallurgy?

Powder Metallurgy, or PM, is a process for forming metal parts by heating compacted metal powders to just below their melting points.

How does powdered metallurgy work?

Step 1: Blending – Powder metal is mixed with a lubricant
Step 2: Pressing – Mixture is pressed into a “green part”
Step 3: Sintering – “Green part” is thermally treated to remove lubricant & strengthen part
Step 4: Finishing (if required) – Strengthened part may be machined and/or steam treated

How can powdered metallurgy help me?

Cost - Powder metal is extremely cost effective, eliminating most machining operations and scrap loss.

Versatility - Powder metal supports a wide variety of alloys, can be heat treated for increased strength, and produces excellent surface finishes.

Complex Designs - Powder metal enables the production of complex parts that would otherwise be near impossible to produce with other metalworking processes.

What type of hydraulic parts can be made with powdered metal?

High strength materials extend the benefits of powder metal technology to numerous hydraulics components including: idler gears, drive gears, pump bodies, hydraulic stators, hydraulic rotors, swash plates, reaction rings, impellers, counterweights, counter balances, eccentrics, gerotor assemblies, commutators, manifolds, wear plates, gear / shaft assemblies, piston pump components (cylinder blocks, shoe retainers, piston shoes, valve plates),  vane pump components (rotor & vanes, cam rings), gerotor pumps, and gear & crescent pumps.

What type of power transmission parts can be made with powdered metal?

High strength materials extend the benefits of powder metal technology to numerous power transmission components including: torque converter hubs, clutch hubs, flange hubs, clutch plates, bevel and pinion gears, pump gears, pump bodies, oil pump rotors, slide, gears, gerotors, parking brake gears, brake components, turbocharger components, pulleys, carriers, counterweights, sprockets, cam sprockets, solenoid components, axle nuts, differential cases, ABS sensor rings, U-Joint components, geometrically contoured bearings, magnetic sensors, A/C clutch hubs, flange hubs, sprockets, oil pump gears, EGR bases, exhaust flanges, clutch plates, carriers, helical & pinion gears, and levers.

What is steam treatment?

Steam treatment is finishing process (step 4) which involves exposing the part at a temperature around 500°C to high pressure steam that leads to the formation of a layer of magnetite (black iron oxide) on all accessible surfaces and a number of desirable property changes. Magnetite (Fe3O4) forms an oxide layer that is typically 5μm-7μm thick at the interconnecting surface porosity, filling the porosity. Magnetite has a hardness equivalent to 50 HRC. Steam treating cannot be described as a heat treatment because no structural changes occur in the matrix. Steam treatment is most effective on parts with a maximum carbon content of 0.5% - 0.8%.

While not necessary for all components, steam treatment benefits include: reducing the susceptibility of ferrous material to rust (Fe2O3), extending shelf life, sealing parts, porosity sealing for hydraulic applications, providing a base material for additional coatings, improving apparent hardness / compressive strength / wear characteristics / certain other mechanical properties, and even providing a decorative coating (producing a blue-gray to blue-black appearance).

Typical applications that benefit from steam treating include: automotive, hydraulics, agriculture, home appliances, lawn and garden, and off-road construction.

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Photo courtesy of Höganäs AB.