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What is the difference between Powder Metallurgy and Casting based traditional manufacturing techniques from an input raw material perspective?

Metal materials are used in wide range of applications, from manufacturing tiny pins to building giant rockets. Manufacturing products out of metal involves the material to undergo numerous processes. The processability of the metal plays an important role in deciding its feasibility for the specific application.

Metal materials are generally processed from two forms – powder and bulk. Each has its own advantages and limitations, handling requirements and manufacturing techniques.

Powder Metals

Powder metal refers to finely divided metal particles of particle size ranging from microns to millimetres. Powders react to its surrounding very rapidly due to its increased surface area. Special attention is needed while handling metal powders as they are sensitive to moisture, highly reactive and prone to oxidation which can deteriorate its processability. Metal powders can be made of single metal or a combination of multiple metals depending on the requirement and application. Powder metals can be processed through some unique techniques:

  • Powder Metallurgy
  • Metal Injection Moulding
  • Additive Manufacturing (3D Printing)

These processes allow metal powders to be manufactured for a wide range of applications in different sectors like automotive, aerospace, medical and consumer electronics.

Bulk Metals

Bulk metal refers to the metal in its solid and dense form, like sheets, bars, billets, or ingots. Bulk metals are widely used across the industries because of its easy availability and reliability. Bulk metals are generally processed through conventional manufacturing techniques:

  • Casting
  • Forming and Machining
  • Welding and Joining

These processes allow bulk metals to be manufactured for a wide range of applications giving a strong and reliable component. Processing bulk metals only lack in manufacturing components having intricate designs.

Powder and Bulk Metals – A Comparative Analysis

Design Flexibility – Bulk metals lack freedom in designing intricate and complex geometries for some special components or parts due to its solid form and limitations of its manufacturing techniques. However, powder metals offer a greater flexibility in terms of design, making it an ideal choice for manufacturing components with complex shapes.

Utilization of Material – Powder metal manufacturing processes like powder metallurgy and additive manufacturing, are very material-efficient, as there is very little material wastage compared to bulk processes. On the other hand, while machining and shaping bulk metals, material wastage is higher. Efficient utilization of materials directly affects cost savings and the need of post processing the raw materials.

In powder metallurgy, scrap rates are to the tune of 3% while in bulk metal processing, this could be as high as 50%! This makes powder metallurgy an obvious economic choice for high value exotic materials.

Material Properties –Bulk metals exhibit excellent mechanical properties, like higher strength, ductility, toughness, and fatigue resistance, because of its structural integrity and homogenous microstructure.

Porosity, which is commonly found in components manufactured from powder metals, is absent in bulk metals, which plays an important role in giving a good mechanical performance.

While on the other hand, powder metals, can give a tailored microstructure depending on its compositional variation, size and distribution of powder and sintering parameters, which can impart even better mechanical properties than the bulk metal. However, porosity plays a villain in imparting good mechanical properties.

Controlling porosity is crucial in processing powder metals. Porosity reduces the overall strength, ductility, fatigue, wear, and corrosion resistance.

Production Scale –Bulk metals, generally processed with casting and forming techniques, are an ideal choice for high-volume production as it is cost effective with lesser lead time and great repeatability. Setup costs can be relatively large but per-unit-cost for such techniques decreases with larger production runs.

Contrary to this, powder metals are suitable for rapid prototyping and low to medium-volume production. Processing time is higher for techniques like additive manufacturing and powder metallurgy. Setup costs can be relatively less, but due to longer processing time and the need for post-processing of powder metal components, per-unit-cost increases.

Summary

To summarize, powder metals and bulk metals have distinct processability and production scaling due to the manufacturing techniques used. Both the forms of metals have their own applications, advantages, and limitations. It is impossible that either one of the forms can replace the other because of their unique processing characteristics.

Of course, they can complement each other by replacing the limitation of one with the strength of other. For example, rapid prototyping can be used to make moulds and dies of intricate shapes for processing bulk metals. In this way, bulk metals can also be given complex shapes with the help of processed powder metals.