Metal powder reuse in additive manufacturing. Alessandro Consalvo AM Support Engineer, Renishaw spa

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1 Metal powder reuse in additive manufacturing Alessandro Consalvo AM Support Engineer, Renishaw spa

2 Renishaw World leading metrology company founded in Skills in measurement, motion control, spectroscopy and precision machining MTT acquisition making Renishaw the only UK manufacturer of metal additive manufacturing systems.

3 Renishaw worldwide locations 70 offices 32 countries > 3800 employees

4 AM250 system AM250 Max Part Build area 245 x 245 x 300 (x,y,z) (z extendable to 360mm) Build rate* 5cm³ to 20cm³ per hour Layer thickness 20 to 100µm Laser beam diameter 70µm at powder surface Laser options 200W or 400W Power supply 230V 1PH 16A Power consumption 1.6 kwh Gas consumption < 30 l/hr * Build rate is dependent on material, density & geometry, not all materials build at the highest build rate.

5 Powder bed laser melting y x 3D model is sliced in layers with thickness from 20 to 100 µm. The machine builds up the part layer by layer, using a high powered fibre laser to fuse fine metal powder particles together. Near net shape metal component with density and mechanical properties comparable to those obtained by casting.

6 How Laser Melting works Powder distributio n System Build Chamber Laser Window Inert Gas Metal Powder Laser beam: 70 µm Build Retractable Platform Z axis A layer of fine gas atomized metal powder is deposited and a high power fiber laser melts the particles together to form solid dense metal following the 3D model. The platform is lowered and a new layer is deposited and melted by the laser. The process is repeated until the merger of the last layer of the model. The unmelted powder is recovered and it can be used again after a sieving process.

7 Powder reuse cycle 1. Fill hopper 2. Inert atmosphere 3. AM 4. Collect overflow 5. Sieve 6. Reuse sieved powder

8 Powder reuse cycle 1. Fill hopper 2. Inert atmosphere 3. AM 4. Collect overflow 5. Sieve 6. Reuse sieved powder

9 Powder reuse cycle 1. Fill hopper 2. Inert atmosphere 3. AM 4. Collect overflow 5. Sieve 6. Reuse sieved powder

10 AM250 inert atmosphere generation Renishaw AM machines are unique in the way build atmosphere is created. All Renishaw systems are suitable for building reactive materials. 1. A vacuum is created, approx.1 atm below ambient: This removes air and any humidity from the entire system 2. The chamber is filled with ~600 litre of high purity argon. 3. The atmosphere is maintained at below 1000ppm (0.1%) oxygen and can be set to run below 100ppm (0.01%) for titanium (Ti6Al4v) and other alloys. Gas consumption is typically <30 L/hr and laser melting is achieved approx. 10 minutes after cycle start.

11 Powder reuse cycle 1. Fill hopper 2. Inert atmosphere 3. AM 4. Collect overflow 5. Sieve 6. Reuse sieved powder Overflow powder down here

12 Powder reuse cycle Overflow capture flasks 1. Fill hopper 2. Inert atmosphere 3. AM 4. Collect overflow 5. Sieve 6. Reuse sieved powder

13 Powder reuse cycle Used overflow powder Sieved used overflow powder 1. Fill hopper 2. Inert atmosphere 3. AM 4. Collect overflow 5. Sieve 6. Reuse sieved powder

14 Powder reuse cycle 1. Fill hopper 2. Inert atmosphere 3. AM 4. Collect overflow 5. Sieve 6. Reuse sieved powder

15 Why investigate powder re-use for AM? An area of AM that needs fully understanding. Feedstock should be reliable for process repeatability and predictability. Powder bed and machine parameters are closely related.

16 Why titanium? High strength to weight ratio High corrosion resistance 45 % lighter than steel $$$$$ Ti-6Al-4V alloy

17 Buy to fly ratio 19 kg Waste Ti 20kg Titanium billet Machining 1 kg Titanium powder AM 1 kg Ti component

18 Powder characteristics - Chemistry Interstitial Alloying Element % Ti Grade 5 Ti Grade 23 (ELI) Oxygen Nitrogen Carbon Hydrogen Aluminium Vanadium

19 Powder characteristics - Physical Density/Packing Flowability PSD Particle size distribution Flowability is important for consistent layers, it is directly influenced by PSD, packing and particle shape. Shape

20 Experimental procedure 20 routine builds using same Ti powder batch in same AM250 system Powder capture capsule Tensile bar and density block Density block Powder analysis Oxygen and Nitrogen PSD Build analysis Tensile Density Flowability Tensile test piece Powder capture capsule

21 Experimental results interstitial elements Maximum O level for grade 23 Steady increasing trend trend. Maximum N level for grade 23 Steady increasing trend trend.

22 Experimental results interstitial elements Grade 5 Maximum Grade 23 Maximum Powder analysis

23 Experimental results Particle size distribution, PSD Build 16 Build 11 No general trend in PSD with increased numbers of builds. Builds 11 and 16 have more wide and narrow distributions respectively.

24 Experimental results - Flowability Flow initially increase between 0-5 builds followed by a general decrease.

25 Experimental results Melted powder: Tensile Upper tensile strength Yield strength

26 Conclusions After 20 builds the powder is not significantly changed either in terms of interstitial elements or physical properties. Results indicate significantly more reuse potential. Careful powder handling contributes to sustainability of powder. Continued investigations required, including blending of powders to sustain repeatability.

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