Powder Metallurgy: An Environmental Sensitive Technology

Powder Metallurgy: An Environmental Sensitive Manufacturing Technology

Most metallic and plastic waste products are currently being crushed into powder and are recycled through P/M processes; by so doing the scrap and other non-biodegradable materials that could have been a menace to the environment are safely put into other uses. Due to this positive impact to the environment, I have been propelled to enlighten the public a bout Powder Metallurgy by giving them a visual summary of the details of this complicated but very important engineering process.

Visual Summary

The process of powder metallurgy entails the preparation of the metal powders, compacting them into shapes and sintering them to give strength, hardness and toughness. Even if the size and weight are limited, the process can be made to produce relatively complicated parts economically, and to close tolerances from a varied range of metals and alloy powders. The control of powder shape/form and quality, process variables and the atmosphere of sintering is an important consideration in product quality. after sintering parts may be put to additional metal working, machining, and finishing operations to impart certain geometric features and improve properties and geometric dimensional accuracy.

The mechanical and physical properties are controlled by the tooling design and the compacting pressure. It is amazing that some critical parts such as jet-engines components are now being made by powder metallurgy techniques. By precisely controlling porosity, products such as filters and oil impregnated bearings can be made.

The P/M process is suitable for medium –to-high volume manufacturing runs and has competitive advantages over other methods of manufacturing such as casting, forging and machining.

Advantages of Powder Metallurgy

• Desirable dimension monitoring: in many cases eliminating the need for machining and finishing operations; thus eliminating scrap, waste and saving energy
• It provides a wide variety of composition to obtain special mechanical and physical properties such as stiffness, damping characteristics, hardness, density, toughness, electrical and magnetic features. It is worth noting that some of the highly alloyed new super alloys are being made into parts by only using P/M manufacturing.
• Powder metallurgy allows for making parts from highly melting-point refractory metals which would be difficulty or uneconomical to make by other methods.
• High production rates on relatively complex parts coupled with automated equipment that requires less labor
• Powder metallurgy allows for impregnation and infiltration for special applications.

Disadvantages of Powder Metallurgy

• There is limited size and complexity of shape of parts and press capacity
• The powder metals costs are very expensive relative to other raw materials
• High costs for equipment tooling for small production runs
• The mechanical properties such as strength and ductility are normally lower than those obtained by forging. However, the properties of full-density P/M parts made by HIP or additional forging can be better than those made by other processes.

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[1] By Geoffrey Kubuli Makhanu[Riresokha]