Metal Powder Applications Increasing
THE MAGAZINE DEVOTED TO NICKEL AND ITS APPLICATIONS
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POWDER METAL PARTS such as these dramatically reduce the leakage of exhaust gases at the junction of the exhaust system and the engine manifold. |
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For more information on the use of nickel-containing materials in the automotive
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Cost-competitive automotive applications are fueling demand for finer nickel powders. By Steve Dawson
Nickel magazine, March, 2004 --Two new nickel powders are enabling manufacturers to make strong, dense auto parts more economically than those crafted from wrought iron or stainless steel. These new powders increase density, improve flexibility, and provide greater strength and hardness in powder metal parts, compared with Type 123 nickel powder, which has been the industry standard since the 1960s.
Inco Special Products (ISP), a division of Inco Ltd., developed the nickel powders, which are known as Type 110 and Type 270.
Type 110 powder contains extra-fine, discrete spherical particles of nickel that are tightly sized in the range of 1 to 2 microns. The finest nickel powder commercially available for powder metal applications, it is designed for high-performance applications. The extra-fine particle size provides greater shrinkage capabilities, which in turn significantly increase the density of the powder metal part. The finer particle size also allows for greater diffusion of the nickel, resulting in a more uniform microstructure with greater toughness and flexibility.
Type 270 powder is a three-dimensional, chain-like network of fine nickel particles produced to tight physical tolerances. When used to produce pressed or sintered powder metal parts, Type 270 provides increase strength, hardenability, and fatigue resistance in nickel steels; it also increases dimensional control and diffusion, which leads to higher ductility and toughness in low-alloy steels.
As a result of recent developments in powder metallurgy, the use of powder metal parts has risen dramatically. Almost any high-volume, intricately crafted part that is highly stressed and requires a high degree of machining is a candidate for powder metal production. Auto parts produced using powder metals include gears, gear carriers, clutch plate holders, rotors, synchronizer hubs, and some ABS components. The average North American-made sport utility vehicle (SUV) has about 20 kilograms of powder metal components, and some models contain as much as 30 kilograms. Applications are so diverse that the automotive industry uses about 70% of all the iron powders produced.
Products manufactured using powder metals first surfaced about 50 years ago in response to changes in the automotive industry. Manufacturers were compelled to find ways to reduce manufacturing costs as competition in the automotive sector increased and profit margins decreased.
Until the late 1950s, all steel automotive parts were machined using either cast iron or wrought steel. Even though these parts possessed superior characteristics, such as a fully dense structure, they were expensive to manufacture, owing to increasing labour costs and the waste generated in machining the part. Manufacturers of auto parts responded by using powders, which were pressed into moulds and heated. This proved economical since a large volume of parts could be created at one time and the capital cost of doing so was lower than the cost incurred by using traditional methods.
Initially, powder metal parts consisted of iron powder, but as the applications became more various, other metal powders, including nickel, copper and molybdenum, were developed and added for special uses. Today, powder metal parts are manufactured using powders typically containing 96% to 98% iron powder and 2% to 4% nickel, copper and/or molybdenum powders.
ISP began manufacturing Inco Type 123 nickel powder in the 1960s. It is a fine, high-purity powder containing discrete particles ranging in size from 3.5 to 4.5 microns, and is produced using Inco's carbonyl process.
Type 123 powder is combined with iron powder, then pressed and sintered to make low-density auto parts. It also binds well with tungsten carbide to manufacture diamond tools and is used as a binder metal with tungsten to manufacture a wide range of other parts. When used as an alloying element in powder metal parts, Type 123 improves strength, hardenability, fatigue characteristics, and resistance to corrosion.
Improved ductility and increased toughness are also achieved as the nickel powder defuses into the steel to form nickel-rich phases. It also promotes shrinkage during the sintering process, which leads to higher density in powder metal parts. And since it promotes shrinkage, Type 123, when used in conjunction with iron and copper powders, can counteract the expansion of copper. As such, nickel powders can provide dimensional control during the sintering process.
Steve Dawson is a Toronto-based freelance writer.
PHOTOS: Metal Powder Industries Federation
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