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Seminário apresentado pelo doutor Santiago Corujeira Gallo, na UCS (Caxias do Sul, RS) em …

Seminário apresentado pelo doutor Santiago Corujeira Gallo, na UCS (Caxias do Sul, RS) em
28 de setembro de 2009. Público: estudantes, professores e pesquisadores da Pós-Graduação em Materiais (PGMat -UCS)

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  • 1. Plasma Surface Engineering Santiago Corujeira Gallo Universidade de Caxias do Sul September 2009
  • 2. Birmingham - UK Founded in middle age (7th century) Population ca 2,500,000 Traditional industrial centre Cultural diversity powered by google maps
  • 3. University of Birmingham Founded in 1900 Research oriented Ranked 12th in UK (RAE) Multicultural over 4000 Intl students from 150 countries Colleges Arts and Law Engineering and Physical Sciences Life and Environmental Sciences Medical and Dental Sciences Social Sciences
  • 4. Surface Engineering Group (2007) Composition of the group: 1 Professor 1 Senior Lecturer / Reader 2 Research fellows 1 Visiting research fellow 7 PhD students 2 MSc students 2 Undergraduate students Topics of research: - Plasma diffusion treatments - Thermal oxidation - PVD coatings - Nanoindentation
  • 5. Active screen plasma surface engineering of austenitic stainless steel for enhanced tribological and corrosion properties • Austenitic stainless steel • Plasma surface engineering • Tribological and corrosion properties • Active screen
  • 6. Austenitic stainless steel • Typical composition: 18% Cr – 8% Ni • AISI 316: 17% Cr – 12% Ni – 2% Mo Typical properties: • Excellent corrosion resistance • Non-magnetic • No ductile-to-brittle transition • Poor mechanical properties • Low wear resistance
  • 7. Surface engineering treatments Benefits of surface engineering • Improved performance • Use cheaper materials • Increase design flexibility Diffusion treatments: • No sharp interface - gradient • Slow (temperature – time)
  • 8. Plasma surface engineering C or N containing gas Conventional gas nitriding ~ 550oC Treated substrate Conventional gas carburising ~ 950oC C or N containing gas at low pressure - - Cr23C6 + Cr1-2N - Treated substrate - cathode (-)
  • 9. GDOES composition depth profiles
  • 10. XRD - phase identification S-phase or expanded austenite
  • 11. Micrographs of expanded austenite Typical cross section optical micrograph Typical top view SEM micrograph
  • 12. Microhardness testing Typical instrumented hardness test curves Typical load bearing capacity
  • 13. Microhardness indents Tough carbon expanded austenite Brittle nitrogen expanded austenite
  • 14. Wear testing Dry sliding pin-on-disc test, 10 N normal load, WC counterpart, 0.03 m/s sliding speed; 4.5 hours
  • 15. Wear results AISI 316 UT AISI 316 PC
  • 16. Morphology of the wear tracks AISI 316 UT AISI 316 PC
  • 17. Wear track of AISI 316 UT
  • 18. Wear track of AISI 316 PC
  • 19. Wear debris Untreated sample: metallic debris Treated sample: oxide debris Wear debris Colour Size Magnetic Possible phases Treated Red / Orange <20um No alpha-Fe2O3 Hematite Un treated Black >20um Yes Fe3O4 Magnetite
  • 20. Wear debris – TEM SAD pattern
  • 21. Wear conclusions • The wear resistance of carbon expanded austenite is 2 orders of magnitude higher than AISI 316 UT • The wear mechanism changes from adhesive wear in AISI 316 UT to oxidational wear in AISI 316 PC • The layer of carbon expanded austenite reduces the subsurface deformation and supports the protective oxide layer
  • 22. Corrosion testing Immersion corrosion Boiling H2SO4 (16%) 1 to 20 hours
  • 23. Corrosion results AISI 316 UT AISI 316 PC After 1 hour immersed in boiling sulphuric acid (16%)
  • 24. Corrosion mechanisms
  • 25. Corrosion mechanisms - Schematic
  • 26. Macrographs of corroded samples AISI 316 UT AISI 316 DCPC AISI 316 ASPC AISI 316 DCPC AISI 316 ASPC Macrographs “as treated”
  • 27. Corrosion conclusions • Carbon expanded austenite exhibits higher corrosion resistance to boiling sulphuric acid than AISI 316 UT • The corrosion mechanisms are defect-controlled (MnS inclusions, slip bands and grain boundaries) • The AS treated samples performed better than the DC ones through the elimination of edge effects
  • 28. Active screen plasma treatments Active Screen experimental setting inside a conventional DC plasma furnace / reactor Nitriding mechanisms of Active Screen - schematics
  • 29. DC and AS plasma reactors
  • 30. Industrial AS plasma furnace
  • 31. AS typical treatment cycle
  • 32. Processing conditions
  • 33. Benefits of AS treatment DC – edge effect DC – arcing damage AS – feature less AS –rusty components before ASPN AS – rusty components after ASPN
  • 34. Active Screen conclusions • AS plasma treatments can produce superior surface quality than DC treatments (no edge effect or arcing damage) • AS treatments are less sensitive to the surface condition of components (rust, oil, etc.) • AS plasma shows potential to further improve the results obtained with DC or other plasma treatments
  • 35. Acknowledgements This project was sponsored by: EU scholarships for Latin America Techint group The University of Birmingham Universidad Tecnológica Nacional
  • 36. Thank you very much indeed