Managing Ti6-4 Powder Degradation Over Multiple Build Cycles

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1 The picture can't be displayed. Managing Ti6-4 Powder Degradation Over Multiple Build Cycles LPW Technology, Inc. Nate Kistler Applications Engineer John D. Hunter General Manager

2 To view AM from the perspective of the powder LPW PowderRange powers >50% global metal AM install base LPW powders advancing AM in over 74 countries PowderRange off-the-shelf rapid delivery solutions Over 50 AM metal powders available for shipment within 48 hours PowderLife production solutions Custom powders, pioneering software, hardware and process solutions for AM production Quality certification AS9100, AS9120 for aerospace, ISO9001 & ISO for medical Servicing safety-critical sectors such as Aerospace, Defense, Medical, Automotive, Energy, Tooling

3 Worldwide network State of the art powder manufacture 7 acre site in Widnes, Liverpool, UK 90,000 sqft² (9,700 M²) Full material traceability Digital Integration Strict contamination control High-tech, low contamination manufacturing: Climate controlled - regulating humidity Air showers / airlocks / positive air pressure Sealed powder containment Allocated cells for individual alloys Dedicated operators for specific processes State-of-the-art laboratory Testing to ISO and NADCAP LPW Technology LPW reseller LPW Joint-Ventures

4 Worldwide network 12,000 sq. ft. (1,115 m2) site Pittsburgh, Pennsylvania, USA Metal powder processing facilities Sieving and blending lines Analytical and reconditioning capabilities Orders typically shipped the same or next day of receipt of order LPW Technology LPW reseller LPW Joint-Ventures

5 Adding powder control reduces risk in AM Comprehensive range of off-the-shelf AM metal powders Sensors to measure powder condition AM powder lifecycle management software Simple powder flow measurement kit Aluminium Cobalt Steel Nickel Titanium Tungsten Carbide Copper Refractory metals Custom alloy development Smart hopper for controlled metal powder storage and transport Powders, products and solutions to support AM in production Analytical testing AM consultancy Materials development Case Studies Why we need control Working with Industry

6 PowderLife Adding Control to the AM Process Mechanical Testing = PowderEye sensor = PowderTrace hopper = PowderLab & PowderFlow

7 Ti-6Al-4V Powder Degradation Recap of last year Powder Bed Fusion Process Unmelted powder reused Sieving process used on reused powder to remove large conglomerates PBF process may influence Powder Shape Particle Size Distribution (PSD) Powder Chemistry Part and Powder Density Mechanical Properties All powder based AM processes cause powder degradation This study: Powder was sieved after each run to remove large agglomerates and refreshed with virgin powder

8 Degradation of Ti-6Al-4V Powder Powder Shape 1 Longest Diameter Shortest Diameter Aspect Ratio D10 D50 D90 AAAAAAAAAAAA RRRRRRRRRR(AAAA) = SSSSSSSSSSSSSSS DDDDDDDDDDDDDDDD LLLLLLLLLLLLLL DDDDDDDDDDDDDDDD Gives information on the circularity of powder particles AR = 1, perfect circle Aspect ratio tends to get more spherical with increasing builds Virgin Oversized 1 Oversized 2 Oversized particles show lowest aspect ratio Splatter

9 Degradation of Ti-6Al-4V Powder Particle Size Distribution Particle Diameter [µm] D90 D50 D10 Range of powder sizes Particle size and distribution tends to increase after a build Sieving brings size and range closer to virgin Oversized particles have the largest diameter and have the largest range 0 Virgin Oversized 1 Oversized Splatter

10 Degradation of Ti-6Al-4V Powder Powder Chemistry - Oxygen Oxygen Concentration [%] Solid Sample O Concentration Powder Sample O Concentration GD5 O Max GD23 O Max Virgin Oversized 1 Oversized Splatter Oxygen content has an influence on the final part s mechanical properties Oxygen increase after first build Sieving out large particles significantly decreases oxygen content General increase with more builds Remains Grade 5 specification until build 10 Oversized particles have largest oxygen content Oxygen content in solid sample slightly higher than powder

11 Degradation of Ti-6Al-4V Powder Part and Powder Density 4.50 Solid Powder Powder density remains constant throughout all builds Density [g/cc] As-built part density decreases with increasing number of builds B2 B3 B4 B5 B6 B7 B8 B9 B10 Build Number

12 Degradation of Ti-6Al-4V Powder Mechanical Properties - Strength As-build part strength properties stay relatively unchanged from Build 1 to Build 10 Strength [MPa] Ultimate Tensile Strength Oxygen Concentration [%] Yield strength and ultimate tensile strength heavily correlated with oxygen content 1050 Yield Strength 1000 Solid Sample Oxygen Concentration 0.15 B2 B3 B4 B5 B6 B7 B8 B9 B10 Build Number

13 Degradation of Ti-6Al-4V Powder Mechanical Properties - Ductility 6% 0.35 Ductility has decreasing trend with build number Elongation at Break [%] 5% 4% 3% 2% Oxygen Concentration [%] Ductility in AM influenced by: Porosity Impurity content Ductility is heavily correlated to oxygen content in present study End of last year s study. 1% Elongation at Break Solid Sample Oxygen Concentration 0% 0.15 B2 B3 B4 B5 B6 B7 B8 B9 B10 Build Number

14 Mechanisms for O and N pick-up Melting process Laser Ti Ti (>>450 C) O and N in atmosphere react with melt pool surface Spatter reacts with O and N, forming O+N rich particles Spatter Powder Solid Ar flow Ar atmosphere O < 1000 ppm N < 4000 ppm O+N rich / TiO x + TiN x Ti powder Spatter Laser On time O+N rich particle falls into powder bed Greater scan area = more spatter More spatter = increased O and N

15 Mechanisms for O and N pick-up Heat affected powder Ti (+ C) Powder bordering part lies in Heat Affected Zone (HAZ) Heat affected powder can pick up O and N Ti (++ C) Low part: powder ratio Higher part: powder ratio = larger area of HAZ High part surface area = larger area of HAZ

16 Mechanisms for O and N pick-up Examples from recycled powder Heat affected powder which has picked up O and N O+N rich particles which have fallen into powder bed Ti (+ C)

17 Mechanisms for O and N pick-up Influence of build layout

18 Ti-6Al-4V Powder Degradation Extended Study Aim Investigation overview Perform study to investigate influence of successive processing on powder and part properties of Ti-6Al-4V Grade 23 material Determine the relationship between build cycle, ONH concentration and mechanical properties Establish and quantify the rate of degradation in relation to input parameters Quantify the impact of the degradation Two methods for powder recycling/refreshing method Top Up Used powder from previous build is topped up with virgin to order to meet the required volume for subsequent build. Continues until virgin powder runs out. Single Batch Builds successively completed until entire batch of virgin material is processed. Remaining exposed powder is sieved and blended, and the cycle is repeated until there is insufficient powder remaining for a full build.

19 Degradation Study Investigation overview Focused on alloy Ti-6Al-4V Grade 23 Additional considerations over previous studies Different recycling methods Testing at different heights Influence on properties important Part and powder properties Conducted on TRUMPF TruPrint LPW UK facility Top Up ran for 30 builds Single batch ran until powder exhausted (29 builds) Both studies used same build layout All builds conducted with oxygen limit set at 1000 ppm

20 Degradation Study Top Up experimental methodology

21 Degradation Study Single Batch experimental methodology

22 Degradation Study Results Oxygen in powder Differences in final oxygen content between regimes In part due to differences in virgin powder In part due to rate of pick up Single batch has increased rate of pick up over same number of builds Increase per exposure is consistent Oxygen Content [Weight %] SSSSSSSSSSSS BB OOOOOOOOOOOO = wwwww TTTTTT UUUU OOOOOOOOOOOO = wwwww Additional 180 ppm by using Single Batch method Build Number Top Up Single Batch

23 Degradation Study Results Oxygen in parts Single batch has greater increase over same number of builds Also has higher starting value Additional 130 ppm using Single Batch method over Top Up SSSSSSSSSSSS BB OOOOOOOOOOOO = wwwww TTTTTT UUUU OOOOOOOOOOOO = wwwww Parts pick up O at similar rate to powder Top up displays power relationship

24 Degradation Study Results Nitrogen in powder Difference in final N content between regimes However this is due to difference in initial N content of virgin powder Increase in N very similar between regimes Nitrogen Content [Weight %] TTTTTT UUUU NNNNNNNNNNgggggg = wwwww SSSSSSSSSSSS BB NNNNNNNNNNNNNNNN= wwwww Pick-up likely driven by atmospheric N concentration Build Number Top Up Single Batch

25 Degradation Study Results Nitrogen in parts Increase in nitrogen similar between regimes Top-up shows power relationship with build number Single batch closer to exponential relationship As with oxygen, implication is atmosphere has greatest influence on N pick up for parts Nitrogen Content [Weight %] Build Number TTTTTT UUUU NNNNNNNNNNgggggg = wwwww SSSSSSSSSSSS BB NNNNNNNNNNNNNNNN= wwwww N - Single Batch N - Top up

26 Degradation Study Results H in powder and parts Neither parts nor powder displayed any discernible pick-up of H, in either reuse regime. Hydrogen is not expected to increase as there is no H naturally present in processing atmosphere Therefore an increase would imply another source of H, most likely water/moisture

27 Degradation Study Degradation metric Oxygen per Total Incident Energy Requirement for metric which is independent of machine/build# Using known values of direct and indirect parameters, able to calculate physical metric Oxygen concentration per Total Incident Energy (TIE) where ddcc oooooooooooo ddee TTTTTT wwwww JJ EE TTTTEE = QQ BBBBBBBB AA TTTTTT QQ BBBBBBBB = PPPPPPPPPP AAAAAAAA AA TTTTTT = TTTTTTTTTT aaaaaaaa cccccccccccccc bbbb llllllllll Single layer All layers

28 Degradation Study Oxygen per Total Incident Top Up vs Single Batch For this case, TIE demonstrates the effect of consistently refreshing with virgin powder In general it allows for direct comparison between different processing regimes: Machine platform Part : Powder ratios Process parameters Reuse regime Oxygen Pick Up [Weight %] E E E E E E+10 Total Incident Energy [J] Top Up Single Batch

29 Degradation Study Summary and Conclusions Summary Two powder replenishment strategies, Top Up and Single Batch, were shown to produce different rates of ONH pick up in both powder and parts Both resulted in increases of O and N of ppm over 30 builds in powder and ppm in parts New metric for measuring degradation introduced weight percent per Total Incident Energy [wt%/j] Conclusions Single Batch method results in significantly greater oxygen pick up (180ppm) than Top Up Difference of 200ppm of O and N in virgin powder is equivalent to 20+ builds Important to start with lowest possible O and N to maximise number of builds Single batch has 5x the rate of oxygen pick up for the same TIE, over Top-Up Important to be able to track and predict at what point powder will fall out of specification. Continued study is underway to determine affect on as-built properties