Laser spray cladding of porous NiTi coatings on NiTi substrates

Y. Q. Yang, Hau Chung Man

Research output: Journal article publicationJournal articleAcademic researchpeer-review

8 Citations (Scopus)

Abstract

Laser spray cladding in N2-rich atmosphere is a competitive technique for manufacture of porous NiTi shape memory alloy (SMA) and TiN surface film. In order to gain expected porous coating and porosity size, TiH2powder was considered to be used as porosity initiating agent, and nitrogen was used for shielding and active nitriding gas. A 2 kW continuous wave Nd:YAG laser equipped with a 3-way coaxial nozzle was used for laser spraying. NiTi alloy powder and TiH2powder were used as additive materials. The mixed powder of NiTi and TiH2was conveyed by a powder feeder, congregated at the laser interacting zone and sprayed onto the substrate with molten droplets. In order to improve the corrosion resistance of the surface of coating layer, a gas nitriding process is facilitated simultaneously during the laser spraying and cladding process in nitrogen-rich atmosphere. A gradient porous coating of NiTi alloy had been manufactured by laser spraying. The investigation shows that there are pores with size of 100-200 μm near the surface. XRD analysis shows that the coating consists of intermetallic compounds NiTi, NiTi2and nitrides TiN, Ti2N. Corrosion test was carried out in Hank's balanced salt solution (H9269) by potentiostat/galvanostat model 273A. The polarization curves of the test result demonstrates the porous coating with TiN presents better corrosion resistance than NiTi substrate.
Original languageEnglish
Pages (from-to)6928-6932
Number of pages5
JournalSurface and Coatings Technology
Volume201
Issue number16-17
DOIs
Publication statusPublished - 21 May 2007

Keywords

  • 3-way coaxial nozzle
  • Laser cladding
  • Laser spraying
  • Porous coating
  • TiN
  • TiNi alloy

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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