Introduction to PM. Marco Actis Grande

Transcription

1 Introduction to PM Marco Actis Grande

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3 What is PM? Materials forming technique Create powders (metallic & non-metallic) Assemble them into artefacts of desired shape Cause the powder particles to adhere strongly to one another (usually at high temperature by means of a process called sintering) Further processing or finishing

4 What is PM? Powder Metallurgy is a continually and rapidly evolving technology embracing most metallic and alloy materials, andawidevarietyofshapes. PM is a highly developed method of manufacturing reliable ferrous and non ferrous parts. The European Market alone has an annual turnover of over Six Billion Euros, with annual worldwide metal powder production exceeding one million tonnes.

5 Once upon a time What is PM? Sintering: a process involved in the heat treatment of green powder compacts at elevated temperatures, usually at T >0.5Tm [K]. By means of this heat treatment a powder compact is densified and gets the desired mechanical properties.

6 The ISO definition of the term sintering states: The thermal treatment of a powder or compact at a temperature below the melting point of the main constituent, for the purpose of increasing its strength by bonding together of the particles.

7 Why PM? Highly developed method for manufacturing reliable ferrous & non-ferrous parts Flexible range of Processes & Materials Wide variety of shapes & sizes Cost savings Linear combination of the former

8 Why PM? Eliminates or minimizes machining by producing parts at, or close to, final dimensions Eliminates of minimizes scrap losses by typically using more than 97% 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.

9 Why PM? An overall (and rough) comparison between different manufacturing techniques The PM process has: The highest raw material utilisation (in most cases over 95%) The lowest energy requirement per kg of finished part

10 When PM? Different production strategies can be at the basis of the use of PM technology: High cost savings: large manufacturing lots, (relatively) complex shapes, small size parts No improvement in properties Higher properties/performance rate Usually higher properties than alternative manufacturing processes Unique way to manufacture

11 Synchroniser hub

12 PM process

13 Forging and machining

14 PM process Forging and machining 43% energy saving

15 Tool steels (I) Conventional ingot Powder metallurgical Conventional hot worked

16 Tool steels (II) non metallic inclusions Carbide size and network

17 Cemented carbides

18 Bearings and Filters

19 FAST techniques

20 History of (industrial) PM W filament Hardmetals and selflubricating bearings Structural parts MIM FAST Additive Late 19th century 1920s 1940s Late 1980s

21 (Main) PM Processes Conventional P/M (press and sinter) Powder Injection Moulding (Hot,Cold) Isostatic Pressing Roll Compacting FAST Techniques Additive Manufacturing

22 PM (and other) Processing PM (Press and sinter) Pressure die casting MIM Parts per Year Cutting technologies Forming technologies Rapid Prototyping Investment casting Low Complexity High

23 Common starting Chemical methods Physical methods Solid State Reduction [Fe] Atomisation (fast solidification) Electrolysis [Fe] Reactions with gases [eg Carbonyl] Hydrogen reduction [W from paratungstate] Mechanical methods: Crushing, milling Mechanical alloying: milling

24 Press and sinter

25 Press Uniaxial Compaction

26 and sinter Steels: C Al & alloys: C Cu & alloys: C

27 Atmospheres 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

28 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 sintering One phase melts. Lot of liquid cannot be allowed - part will slump Liquid flows into available space and reorganises the solid particles Diffusion is much faster in liquid. Ex: Hard metals, WC with Co binder

29 Metal Injection Moulding 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.

30 Isostatic pressing Cold Hot

31 Cutting tools Hard metal Cermets Diamond tools

32 Roll compaction

33 EDC/EDS

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35 Additive Manufacturing

36 Additive Manufacturing

37 Additive Manufacturing

38 Additive Manufacturing PBF Technology DED Technology

39 EBM Technology

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42 Hydraulic manifold built using EBM technology Courtesy: ORNL Medical implant application using: (left) DMLS technology. (right) EBM technology

43 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.

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