22-04-2014, 04:56 PM
INTRODUCTION TO POWDER METALLURGY
Powder Metallurgy
The process by which fine powdered materials are
blended, pressed into a desired shape, and then heated to
bond powder particles.
• Used when large quantity of small, intricate parts with
high precision are required.
• Little material waste and unusual mixtures can be
utilized.
• Used when other methods like casting, machining are
not suitable.
• Used for parts in defence, automotive industry,
household appliances, and recreational equipment
Why Powder Metallurgy is Important
• PMparts can be mass produced to net shape or near net shape, eliminating
or reducing the need for subsequent machining.
• PM process wastes very little material - about 97% of the starting
powders are converted to product.
• PM parts can be made with a specified level of porosity, to produce
porous metal parts.
• Certain metals that are difficult to fabricate by other methods can be
shaped by powder metallurgy.
• Certain alloy combinations made by PM cannot be produced in other
ways.
• PM compares favorably to most casting processes in dimensional
control.
Powder Characteristics
• Properties of powder metallurgy products are highly
dependent on the characteristics of starting
powders
• Some important properties and characteristics
Chemistry and purity
Particle size
Size distribution
Particle shape
Surface texture
• Useful in producing prealloyed powders
– Each powder particle can have the desired alloy composition
Powder Mixing and Blending
• The majority of powders are mixed with
other powders, binders, and lubricants to
achieve the desired characteristics in the
finished product
• Sufficient diffusion must occur during
sintering to ensure a uniform chemistry
and structure
• Unique composites can be produced
• Blending or mixing operations can be done
either wet or dry