NI-BASED SUPERALLOY INCONEL 625 MANUFACTURED BY ELECTRON BEAM MELTING

Transcription

1 NI-BASED SUPERALLOY INCONEL 625 MANUFACTURED BY ELECTRON BEAM MELTING EBAM Conference Nürnberg 2016 Edouard CHAUVET 1, Guilhem MARTIN 1, Rémy DENDIEVEL 1, Jean- Jacques BLANDIN 1, Benjamin VAYRE 2, Stéphane ABED 2 (1) Université Grenoble Alpes, SIMAP-F Grenoble, France (2) Poly-Shape, Salon de Provence, France 1

2 INTRODUCTION CONTEXT AND SUBJECT Grenoble University PhD in collaboration with Poly-Shape : Material development for Electron Beam Melting 5 cm Arcam A1 machine in Grenoble First EBM in French University (since 2012 ) Industrial problematic : increasing demand for Ni-based superalloy Possibility to manufacture superalloy by EBM? - Systematic approach for EBM parameter development - Example of Inconel 625 2

3 OUTLINE 1. INITIAL POWDER CHARACTERIZATIONS 2. METHODOLOGY FOR PROCESS PARAMETER DEVELOPMENT 3. MICROSTRUCTURAL CHARACTERIZATIONS 4. CONCLUSIONS AND PERSPECTIVES 3

4 N/No 1. INITIAL POWDER INCONEL 625 POWDER CHARACTERIZATIONS Material : Element Ni Cr Mo Fe Nb Ti Al Wt % bal 21,52 8,64 3,95 3,51 0,19 0,21 - Pre-alloyed powder of Inconel 625 from Praxair - Matrix of NiCr (fcc) strengthened by solid solution (Mo, Nb) - Particle density of 8.26 ± 0.17 g.cm -3 (pycnometer) Size distribution and morphology : - Particle size : µm - Spherical particles with satellites (Gas Atomisation) 25 Satellites µm Particle size (µm) 200 µm 4

5 N/No 1. INITIAL POWDER INCONEL 625 POWDER CHARACTERIZATIONS Internal porosity in powder: Spherical porosity = trapped gas during atomization 200 µm 10 µm Total particles With porosity Particle size (µm) 0.45% of porosity in powder Around 6% of the particles No correlation with particle size 5

6 OUTLINE 1. INITIAL POWDER CHARACTERIZATIONS 2. METHODOLOGY FOR PROCESS PARAMETER DEVELOPMENT 3. MICROSTRUCTURAL CHARACTERIZATIONS 4. CONCLUSIONS AND PERSPECTIVES 6

7 2. PROCESS PARAMETER DEVELOPMENT PARAMETER DEVELOPMENT FOR EBM Smoke test First parameter window for no powder explosion Sintering test Process temperature (dilatometry and in situ tests) T build 900 C related to an average current Pre-heating test Powder layer pre-heating avoiding smoke and delamination Parameters adapted from the average current Melting parameters and strategy Determination of melting parameters : 2 examples based on DOE 7

8 Bottom temperature ( C) 2. PROCESS PARAMETER DEVELOPMENT MELTING STEP : FIRST DESIGN OF EXPERIMENT (DOE) Variations of 2 parameters (Auto-calculation mode) : - Focus offset beam spot size / 0-50 ma - Speed function scan speed / ( mm/s) Samples 23 x 23 x 25 mm melted with the same beam power ( I = 8 ma) Porous Well melted Over melted 20 mm Building step Cooling step Time (h) 8

9 2. PROCESS PARAMETER DEVELOPMENT MAP OF RELATIVE DENSITY Each sample density is measured by the Archimede s Method : Powder relative density : ρ powder /ρ ref = 0,995 (dotted line) Samples with additional porosity because of the process : ρ samples /ρ ref < 0,995 Processing window in term of density 9

10 2. PROCESS PARAMETER DEVELOPMENT MAP OF THE TOP SURFACE SHAPE Relative density criterion integrated with the top surface shape classification : Process parameter window Selection of parameters: - Speed function = 70 Focus Offset = 25 ma - maximum speed process and sharpest beam spot 10

11 Surface Energy (J/mm²) 2. PROCESS PARAMETER DEVELOPMENT MELTING STEP : 2 ND DOE Variations of 2 parameters (Manual mode) : - Beam Intensity / 2-20 ma - Scan speed / mm/s 18,00 16,00 Over melted 14,00 12,00 10,00 Well melted Porous E s = U I beam V scan δ line offset 8,00 6,00 4,00 Es range = processing window 2,00 0, Scan speed (mm/s) When scan speed increases the E s needed decreases because of the reduction of the heat conduction time [Inconel 718 Helmer et al. (2014)] 11

12 OUTLINE 1. INITIAL POWDER CHARACTERIZATIONS 2. PROCESS PARAMETER WINDOW FOR THE MELTING STEP 3. MICROSTRUCTURAL CHARACTERIZATIONS 4. CONCLUSIONS AND PERSPECTIVES 12

13 Counts (10 6 ) 3. MICROSTRUCTURAL CHARACTERIZATION MICROSTRUCTURE OF EBM SAMPLE Well melted sample from the selected parameters (Auto-calculation): - Columnar grains microstructure oriented with the building direction - Platelets precipitates organized in columns - Typical EBM microstructure pointed out by Murr et al (200) 20 µm EBM Sample Initial powder (400) θ ( ) 13

14 3. MICROSTRUCTURAL CHARACTERIZATION EFFECT OF PROCESS PARAMETERS Microstructure of 3 samples with different top surface shapes: - Scan speed and focus offset are constant Porous - Only beam intensity is varying : 3, 5 et 12 ma Well melted Over melted X Z Y 500 µm 500 µm P 5% P 0,4% P 0,2% Porosity : - lack of fusion - higher melted volume : gas have more time to get out of the melt pool 14

15 3. MICROSTRUCTURAL CHARACTERIZATION EFFECT OF PROCESS PARAMETERS A2 = Building Direction Grain size and orientation : EBSD MAP Porous sample A3 A1 A2 300 µm 300 µm - Grain growth process : nucleation from the first melted layer and epitaxial growth with the successive layer melting - Preferential growth of grain oriented with the building direction 15

16 3. MICROSTRUCTURAL CHARACTERIZATION EFFECT OF PROCESS PARAMETERS A2 = Building Direction Grain size and orientation : Well melted sample 300 µm 300 µm 300 µm - Oriented grain microstructure [001] with the building direction - Constant average grain width along the sample height 100 µm 16

17 Grain width (µm) 3. MICROSTRUCTURAL CHARACTERIZATION EFFECT OF PROCESS PARAMETERS A2 = Building Direction Grain size and orientation : Over melted sample 300 µm 300 µm 300 µm Height (mm) - Grain size variation with the sample height ( µm) - Related to higher beam power (melt pool morphology) 17

18 4. CONCLUSIONS AND PERSPECTIVES CONCLUSIONS Methodology for process parameter development Feasibility of superalloy Inconel 625 by EBM Relations between sample microstructures (grain size and orientation) and process parameter (beam intensity, scan speed, focus offset) PERSPECTIVES Using this methodology for other superalloys Designing microstructures playing with melting parameters and strategy Mechanical properties characterizations 18

19 THANK YOU FOR YOUR ATTENTION Questions? PhD funded by the Labex Center of Excellence in Multifuntional Architectured Materials 19