Powder Metallurgy Properties: Important Considerations for Parts Design and DevelopmentFebruary 14, 2020
Many manufacturing companies have resorted to powder metallurgy (PM) as a way to create products out of metal. The steps behind powder metallurgy involve the mixture of elemental or alloy powders through compacting them in a die. After the compacting process, the new mixture is then sintered or heated at high temperature to further solidify and bond the metal product together.
Powder metallurgy as a metal-forming technology has benefited a lot of manufacturing companies. Companies are now free to choose from a wide range of metal or non-metal powders in creating their products. Moreover, this technology enables them to save a lot of resources such as money and energy. Also, companies can now obtain a good surface finish with every product that they produce.
If your company wants to maximize the advantages of PM, then you should consider these properties when designing and developing PM products and parts.
Defined as the mass per unit volume, density is important when processing PM parts. Determining the density of structural parts is reported on a dry, un-impregnated basis, while the density of bearings is assessed on a fully oil-impregnated basis.
Density can also be expressed as relative density. PM parts are classified as low density if they have less than 75% of relative density, medium density if they have between 75% to 90% of relative density, and high density if they have above 90% of relative density. Structural parts have relative densities around 80% to 95%, while self-lubricating bearings have relative densities of 75%.
Porosity is a measure of the void or empty spaces in a part. It is a network of interconnected pores that can reach the surface of the PM parts. PM parts can be produced with either a uniform percentage of porosity or varying percentage of porosity on their specific sections.
Both porosity and density of PM parts can affect their corrosion resistance. If a PM part has high density, then its corrosion resistance will improve significantly. Stainless steel PM parts have good corrosion resistance against the atmosphere and weak acids.
Depending on the sintering techniques, the permeability of a PM part determines its ability to let liquid or gas pass through them. A PM part can provide permeability that ranges from highly restricted to open flow.
The tensile strength of a PM part determines its resistance to breaking under tension. It points out the maximum stress a material can hold while being stretched or pulled before breaking. Yield strength, on the other hand, is the stress a material can withstand without any deformation. PM materials and parts out of stainless steel have higher yield strength compared to other materials.
Ductility is the ability of a material to be stretched under tensile stress. The ductility in PM materials and parts is relatively low since they have pores. For ferrous materials such as alloy steel and carbon steel, the elongation level is less than 10%. PM brasses and stainless steels, however, have an elongation level that ranges between 15% and 25%.
Knowing these properties will certainly help you produce the best products out of PM. To know more about this metal-forming technology, you can give us a call at PM Distributors.
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