BENCHMARKING SUMMARY BETWEEN SLM AND EBM RELATED TO POWDER RECYCLING.

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1 BENCHMARKING SUMMARY BETWEEN SLM AND EBM RELATED TO POWDER RECYCLING. In the ManSYS project a method has been specified which examines components for meeting required specifications (qualifying criteria) in a repeatedly manner, so they can be identified as qualified. This method is based on the requirements specified in the standard ASTM F , ASTM F and the expertise from experts with complementary background. The developed method could be considered as reference for qualifying other metal alloys using full melt powder bed fusion such as electron beam melting and laser melting. Two different studies related to FeedStock control were developed: 1. Validation of recycled powder and correlation between powder and bulk material in terms of chemical composition. Two procedures were defined as a guideline for feedstock controlling: Assessment of the amount of inclusions and impurities present in the chemical composition of the feedstock. The assessment of the chemical composition in the material as built will serve to ascertain if the final material chemistry is in accordance with the table 1 of the ASTM F or F However, the assessment of the chemical composition in the powder prevents non-conformities for build cycles before processing. Assessment of the feedstock properties variation along several build cycles. This study considers the assessment of the properties variation in both, powder and as built material as well, when the same powder lot is processed several times in different build cycles in a machine. Powder properties assessed shall be chemical composition, size distribution, particle shape, tap density and flow rate. As built material property assessed shall be chemical composition. This study allows gathering important information about the feedstock such as, the identification of the critical element in the chemical composition; and a correlation of the percentages by weight of the critical element between the as built material and powder. These information shall drive the procedure for blending the powder and shall provide the maximum number of times used powder can be used as well as the number of any portion of a powder lot can be processed in the build chamber should be agreed upon between the component supplier and purchaser for Class A, B, C, D and F. 2. As built (bulk) material characterisation into the critical element limits. Once the feedstock studies described in the previously have been conducted, the critical element has been identified and the powder blending has been specified, a procedure for bulk material characterization was developed. Using as feedstock, several samples with a percentage by weight of the critical element into the minimum and maximum values specified in the table 1 of ASTM F or ASTM F3001. That means, the 1

2 structural properties of the bulk material shall be predictable if it is processed from any feedstock with a percentage by weight of the critical element into these values. Procedures for developing these studies were defined and followed for EBM and SLM technologies for Ti6Al4V processing. Next tables show a benchmarking summary between these technologies related to powder recycling and contain all results obtained from these studies. VALIDATION OF RECYCLED POWDER AND CORRELATION BETWEEN POWDER AND BULK MATERIAL IN TERMS ON CHEMICAL COMPOSITION - FEEDSTOCK CONTROL Assessment of the amount of inclusions and impurities in the chemical composition of the feedstock Parameter Impurities SLM TECHNOLOGY SLM Realizer at TWI As built material: EBM TECHNOLOGY Arcam A2 at AIMME Powder: Cr (%) = < 0.1 Cu (%) = < 0.1 Ni (%) = < 0.1 Detected impurities are according to ASTM F and ASTM F Cr (%) = < 0.1 As built material: Cr (%) = < 0.1 Ni (%) = < 0.1 Detected impurities are according to ASTM F and ASTM F Assessment of the feedstock properties variation along several build cycles. Parameter SLM TECHNOLOGY EBM TECHNOLOGY Powder Chemical Analysis Nitrogen and Hydrogen remain within ASTM spec for Ti6Al4V Grade 5 and 23, ASTM F and ASTM F Oxygen starts in the virgin powder meeting Grade 23 and grade 5 but after use the maximum limit for Grade 23 is passed. Oxygen content broads the maximum limit in as built material before than powder. Oxygen picks up at a rate of 20ppm per 20 builds Iron and Vanadium: The content of Iron was always maintained near 0.15%. No decrease in Iron content was observed after consecutive builds. The evolution of Vanadium was kept the same levels as the fresh powder. The content of Aluminium is decreased during the consecutive builds but maintaining always within the limits according to ASTM F and ASTM F The evolution of the Hydrogen content was at very low level. The evolution of the Oxygen content increases in Titanium made on EBM. Oxygen content is lower in as built (bulk) material than in powder for the same build cycle. 2

3 Morphological powder analysis: Flow rate does not change with increasing number of build cycles. Particle size distribution does not change with increasing number of build cycles. The particle shape appears to change and become more spherical with repeated use. Tap density: Build 1: 2.9 g/cm 3 Build 5: 2.9 g/cm 3 Build 10: 3 g/cm 3 Flow rate: Build 1: s Build 3: s Particle size distribution remains constant throughout all builds. Powder shape and form remained constant. Tap density: Build 1: 2.35 g/cm 3 Build 3: g/cm 3 As built (bulk) material chemical composition analysis Critical element in the final chemistry Correlation of the percentages by weight of the critical element between as built material and powder It is evaluated the percentage by weight of Oxygen content in the as built material: Build 2: O(%) = Build 3: O(%) = Build 4: O(%) = Build 5: O(%) = Build 6: O(%) = Build 7: O(%) = Build 8: O(%) = Build 9: O(%) = Build 10: O(%) = Oxygen content % Oxygen (as built) = % Oxygen (powder) It is evaluated the percentage by weight of Oxygen content in the as built material: Build 1: O(%) = Build 2: O(%) = Build 30: O(%) = Build 31: O(%) = Build 38: O(%) = Build 39: O(%) = Build 40: O(%) = Build 41: O(%) = Oxygen content % Oxygen (as built) = % Oxygen (powder) Table 1. Results for feedstock control: SLM vs. EBM. 3

4 AS BUILT (BULK) MATERIAL CHARACTERISATION INTO THE CRITICAL ELEMENT LIMITS Parameter SLM TECHNOLOGY EBM TECHNOLOGY Yield strength (MPa). BUILD 2: BUILD 3: BUILD 4: BUILD 5: BUILD 6: BUILD 7: BUILD 8: BUILD 9: BUILD 10: Build 1-1: Build 1-2: Build 1-3: Build 1-4: Build 1-5: Build 1-6: Build 1-7: Tensile strength (MPa) BUILD 2: BUILD 3: BUILD 4: BUILD 5: BUILD 6: BUILD 7: BUILD 8: BUILD 9: BUILD 10: Build 1-1: Build 1-2: Build 1-3: Build 1-4: Build 1-5: Build 1-6: Build 1-7: Elongation (%) BUILD 2: 4.81 BUILD 3: 4.15 BUILD 4: 4.89 BUILD 5: 4.20 BUILD 6: 4.16 BUILD 7: 4.73 BUILD 8: 2.43 BUILD 9: 3.03 BUILD 10: 3.86 Build 1-1: 16 Build 1-2: 14.5 Build 1-3: 14.5 Build 1-4: 16 Build 1-5: 14.5 Build 1-6: 17.5 Build 1-7: 14 Reduced Area (%) BUILD 2: BUILD 3: BUILD 4: BUILD 5: BUILD 6: BUILD 7: BUILD 8: 6.13 BUILD 9: 6.64 BUILD 10: 9.60 Build 1-1: 42 Build 1-2: 34 Build 1-3: 41 Build 1-4: 46 Build 1-5: 41 Build 1-6: 45 Build 1-7: 42 Table 2. As built material characterisation with a feedstock into the critical element limits. 4

5 References AS Quality Systems Aerospace Model for Quality Assurance in Design, Development, Production, Installation and Servicing. ASTM B212. Test Method for Apparent Density of Free-Flowing Metal Powders Using the Hall Flowmeter Funnel. ASTM B213. Test method for flow rate of metal powders using the hall flowmeter funnel. ASTM B214. Test Method for Sieve Analysis of Metal Powders. ASTM B243. Standard Terminology of Powder Metallurgy ASTM B822. Test Method for Particle Size Distribution of Metal Powders and ASTM E11. Specification for Woven Wire Test Sieve Cloth and Test Sieves. ASTM E112. Standard Test Methods for Determining Average Grain Size. ASTM E1409. Test method for determination of Oxygen and Nitrogen in titanium and titanium alloys by Inert gas fusion. ASTM E1447. Test method for determination of Hydrogen in titanium and titanium alloys by inert gas Fusion thermal conductivity/infrared detection method. ASTM E1941. Test method for determination of Carbon in Refractory and reactive metals and their alloys by combustion analysis. ASTM E2371. Test Method for Analysis of Titanium and Titanium Alloys by Direct Current Plasma and Inductively Coupled Plasma Atomic Emission Spectrometry (Performance-Based Test Methodology). ASTM E3. Guide for Preparation of Metallographic Specimens. ASTM E407. Practice for Microetching Metals and Alloys ASTM E539. Test Method for Analysis of Titanium Alloys by X-Ray Fluorescence Spectrometry. ASTM E8/E8M. Test methods for tension testing of metallic materials. ASTM F Standard Specification for Additive Manufacturing Titanium-6 Aluminum-4 Vanadium with Powder Bed Fusion. ASTM F Standard Specification for Additive Manufacturing Titanium-6 Aluminum-4 Vanadium ELI (Extra Low Interstitial) with Powder Bed Fusion. ISO Medical devices Quality management systems Requirements for regulatory Purposes. ISO General requirements for the competence of testing and calibration laboratories. 5

6 ISO Welding - Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding excluded) - Quality levels for imperfections, ISO : Destructive tests on welds in metallic materials - Hardness testing - Part 1: Hardness test on arc welded joints. ISO Industrial Woven Wire Cloth Technical Requirements and Testing. Related Compounds by Light Scattering. ISO 9000, Quality management ISO Quality Management Systems 6