powder metallurgy

what decided the choice of powder production method?

particle size, morphology, microstructure, cost

molten metal breaks into small droplets by rapidly freezing them before the droplets come into contact with each other or with solid surface

atomization

factors that affect particle morphology and size in atomization

solidification rate, pressue and volume of atomizing fluid, thickness of metal stream

less spherical, more irregular particles

water atomization

spherical, better flow, can contain trapped gas

gas atomization

rotating bar melted by induction, drips into gas, no crucible contact

EIGA

rotating electrode melted by plasma, centrifugal ejection, spherical

PREP

wire fed into plasma torches, fine spherical

PA

cheaper compromise, more entrapped gas

centrifugal

hydrogenate, mill powder, heat (has a rough morphology)

hydrogenate TiH2

nonspherical powder is injected into a plasma, melts quickly, forms spheres, then is quenched

plasma spheroidization

smaller particles are

stickier

assisting consolidation through uniaxial pressure

pressing

containment of the part and application of hydrostatic pressure

isostatic pressing

miscellanous shaping examples

rolling, injection molding

heating a green compact below melting point so that particles bond

sintering

stages of solid-state sintering

neck formation, intermediate, late

factors that affect sintering

high temp, high density, atmosphere, particle size distribution