introduction to pm - epma

Marco Actis Grande

Introduction to PM

EPMA Powder Metallurgy Summer School 2016 - Valencia


• Materials forming technique• “Create” powders (metallic & non-metallic)• Assemble them into artefacts of desired shape

• Cause the powder particles toadhere strongly to one another(usually at high temperature bymeans of a process calledsintering)

• Further processing or finishing

What is PM?


Powder Metallurgy is acontinually and rapidly evolvingtechnology embracing mostmetallic and alloy materials,and a wide variety of shapes.PM is a highly developedmethod of manufacturingreliable ferrous and nonferrous parts. The EuropeanMarket alone has an annualturnover of over Six BillionEuros, with annual worldwidemetal powder productionexceeding one million tonnes.

What is PM?


Once upon a time…

What is PM?

Sintering: a process involved in the heat treatment of“green” powder compacts at elevated temperatures, usuallyat T > 0.5Tm [K]. By means of this heat treatment a powdercompact is densified and gets the desired mechanicalproperties.


The ISO definition of the term “sintering” states:

“The thermal treatment of a powder or compact at atemperature below the melting point of the main constituent,for the purpose of increasing its strength by bonding togetherof the particles.”


Why PM?

• Highly developed method for manufacturing reliableferrous & non-ferrous parts

• Flexible range of Processes & Materials

• Wide variety of shapes & sizes

• Cost savings

• Linear combination of the former


• Eliminates or minimizes machining by producing parts at, or closeto, final dimensions

• Eliminates of minimizes scrap losses by typically using more than97% of the starting raw material in the finished part.

• Permits a wide variety of alloy systems.• Produces good surface finishes.• Provides materials which may be heat-treated for increased strength

or increased wear resistance.• May provide controlled porosity for self-lubrication or filtration.• Facilitates the manufacturing of complex or unique shapes which

would be impractical or impossible with other metalworking processes.• Is suited to moderate to high volume component production

requirements.• Offers long-term performance reliability in critical applications.• Is cost-effective.

Why PM?


An overall (and rough) comparison between differentmanufacturing techniques…

The PM process has:

• The highest rawmaterial utilisation (inmost cases over 95%)• The lowest energyrequirement per kg offinished part

Why PM?


When PM?

Different production strategies can be at the basis of theuse of PM technology:

• High cost savings: large manufacturing lots, (relatively)complex shapes, small size parts

No improvement in properties

• Higher properties/performance rateUsually higher properties than alternativemanufacturing processes

• Unique way to manufacture


Synchroniser hub


PM process


Forging and machining


Forging and machining

PM process

43% energy saving


Powder metallurgical

Conventional ingot

Conventional hot worked

Tool steels (I)


non metallic inclusions

Carbide size andnetwork

Tool steels (II)


Cemented carbides


Bearings and Filters


FAST techniques

www.ifam.fraunhofer.de


History of (industrial) PM

W filament

Hardmetalsand self‐lubricatingbearings

Structuralparts MIM FAST Additive

Late 19thcentury

1920s 1940s Late 1980s 2000 2010


• Conventional P/M (press and sinter)• Powder Injection Moulding• (Hot,Cold) Isostatic Pressing• Roll Compacting• FAST Techniques• Additive Manufacturing• …

(Main) PM Processes


Rapid Prototyping

MIM

Low Complexity High

Cut

ting

tech

nolo

gies

Form

ing

tech

nolo

gies

PM (Press and sinter)

106

105

104

103

102

10

1

Par

ts p

er Y

ear

Pressure die casting

Investment casting

PM (and other) Processing


Chemical methods

Solid State Reduction [Fe]

Electrolysis [Fe]

Reactions with gases[eg Carbonyl]

Hydrogen reduction[W from paratungstate]

Physical methods

Atomisation(fast solidification)

Mechanical methods:Crushing, milling

Mechanical alloying:milling

Common starting


Press and sinter


Uniaxial Compaction

Press


Steels: 1100 – 1300 °CAl & alloys: 590 – 620 °CCu & alloys: 750 – 1000 °C

…and sinter


Gaseous environments for sintering

• Chemically active: reducing

• for steels, carbon potential of the atmosphere should be in equilibrium with carbon content of the steel

• Much more demanding requirements for materials with greater affinity for oxygen,Al, stainless steel, etc

Atmospheres


Alloying during sintering• pre-alloyed powders; hard but uniform

• mixed elemental powders; inter-diffusion during sintering generally not complete, providing non-uniform microstructures

Liquid phase sinteringOne phase melts. Lot of liquid cannot be allowed - part will slump

Liquid flows into available space and re-organises the solid particles

Diffusion is much faster in liquid.

Ex: Hard metals, WC with Co binder


Metal injection moulding (MIM) is a manufacturing process which combines the versatility of plastic injection moulding with the strength and integrity of machined, pressed or otherwise manufactured small, complex, metal parts.

Metal Injection Moulding


Isostatic pressing

ColdHot


Cutting toolsHard metalCermetsDiamond tools


Roll compaction


EDC/EDS


Additive Manufacturing


DED Technology

PBF Technology

Additive Manufacturing


EBM Technology


Hydraulic manifold built using EBM technologyCourtesy: ORNL

Medical implant application using:(left) DMLS technology. (right) EBM technology


A lightweight seat buckle with hollow structures was designed based on extensive FEA study to ensure enough strength against shock loading. The part was produced using DMLS Ti-6Al-4V alloy.

Replacement of a conventional steel buckle with hollow AM titanium buckle causes 85 g weight saving per buckle (55% weight reduction).

An Airbus A380 with 853 seats will result in a possible weight saving of 72.5 kg.

According to the project sponsor, Technology Strategy Board, United Kingdom, this weight saving translates to 3.3 million liters of fuel saving over the life of the aircraft that is equivalent to £2 million, while cost of making all the buckles using DMLS is only £165,000 .

introduction to pm - epma

Documents