Stefano Saccarola

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Stefano Saccarola

  1. 1. DEVELOPMENT OF IRON BASE POWDERS SUITABLE FOR LASER WELDING S. Libardi*, S. Saccarola** , C. Poli***, C. Menapace*, A. Molinari* * University of Trento ** Pometon S.p.A. Venice - Italy. *** Pentax srl Marostica (VI), Italy
  2. 2. Stone cutting: the evolution
  3. 3. Stone cutting: the evolution
  4. 4. Stone cutting: the evolution In 1953 first synthesis of an artificial diamond
  5. 5. Diamond tools used for cutting of stones and other hard construction materials
  6. 6. Laser welding Laser welding needs a diamond free mixture Common backing material composition is Co , Ni , Fe based powder Backing material Complex (metallic matrix with diamonds)
  7. 7. <ul><li>A good product for laser welding has to show: </li></ul><ul><li>Good welding quality </li></ul><ul><li>Sintering temperature compatible with complex </li></ul><ul><li>Sintering Pressure compatible with complex </li></ul><ul><li>No impurity production during laser welding </li></ul><ul><li>Attractive price </li></ul>With these references, we started to develop a new product for this application, an iron based powder with some addictives
  8. 8. <ul><li>A new alloy based on the Fe-Ni-Co system </li></ul><ul><li>Delevoped and tested in production </li></ul><ul><li>Good properties, similar to conventional backing materials </li></ul><ul><li>Match the EN 13236 standard requirement </li></ul><ul><li>Co addiction enhances sintering (lower temperature 800°C - less pores, more rounded) </li></ul>
  9. 9. <ul><li>To increase the hardness and toughness of the alloy due to microstructural refining </li></ul><ul><li>To match a good compressibility in order to reach a full density we used also a mixture between mixed powder and milled one </li></ul>Mechanical alloying
  10. 10. Experimental procedure: Two powders used: Fe-Ni (Ni 10%) Extrafine Co Mixed and ball milled for 20 h then we test three powder mixtures: - simply mixed powder - milled powder - 50-50 mixture of them
  11. 11. <ul><li>mixed powder milled powder </li></ul>Morphology
  12. 12. Densification Densification curves of the mixed and milled powders after hot pressing at 900°C 516 ±7 HV0.05 7.96 Milled 213 ±28 HV0.05 8.07 Mixed Microhardness Density (g/cm 3 ) Powder
  13. 13. Microstructures microstructure of the 900°C hot pressed milled powder microstructure of the 900°C hot pressed mixed powder
  14. 14. XRD analysis milled powder mixed powder 4 % 1 % 95 % Milled 22 % 15 % 63 % Mixed Ni(Co) fcc Fe(Ni) fcc Fe(Ni) bcc Material
  15. 15. Mixing 50 – 50 of them.. Density of the different materials versus the hot pressing temperature
  16. 16. Hot pressing at 800°C mixed milled “ mixed+milled” microhardness
  17. 17. Mechanical properties (1) three points bending curves of specimens obtained with the mixed powder tensile curves of specimens obtained with the mixed powder
  18. 18. Mechanical properties (2) three points bending curves of specimens obtained with the milled powder tensile curves of specimens obtained with the milled powder
  19. 19. Mechanical properties (3) three points bending curves of specimens obtained with the mixture of the two powders tensile curves of specimens obtained with the mixture of the two powders
  20. 20. Conclusions <ul><li>An experimental Fe-Ni-Co powder has been investigated as a backing material, and processed by mixing and milling; </li></ul><ul><li>Mixed powder reach fully densification </li></ul><ul><li>Milled powder not fully densified </li></ul><ul><li>Mix + mill mixture very close to theoretical density </li></ul>
  21. 21. Conclusions <ul><li>Milled powder shows brittle behaviour </li></ul><ul><li>Mix + mill increase mechanical properties, showing a plastic behaviour, </li></ul><ul><li>but has a inhomogeneous microstructure, due to large particle size of milled powder </li></ul><ul><li>Optimization of milling parameters to increase homogeneity in microstructure and microhardness </li></ul>
  22. 22. Acknowledgements Università di Trento
  23. 23. Thank you for your attention

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