Boride Coatings Obtained by Pack Cementation Deposited on Powder Metallurgy and Wrought Ti and Ti-6Al-4V Articles uri icon

publication date

  • December 2010

start page

  • 2340

end page

  • 2347

issue

  • 7

volume

  • 205

international standard serial number (ISSN)

  • 0257-8972

electronic international standard serial number (EISSN)

  • 1879-3347

abstract

  • Wear resistance of Ti alloys needs to be improved, and an effective way to achieve this is through surface treatment. Boronizing is a surface treatment in which boron diffuses into the surface of Ti leading to the
    formation of hard and wear-resistant Ti borides. Boronizing of wrought
    and/or cast Ti alloys by pack cementation has been studied, while
    similar coatings on Ti alloys produced by powder metallurgy (PM) have
    not been reported. Also critical process parameters for boronizing Ti
    alloys, such as pack cementation powder composition and the process
    temperature have not been systematically studied and analysed. The
    present work reports on the surface modification of PM Ti and PM
    Ti&-6Al&-4V by boronizing, and presents some important thermodynamic
    aspects of the process comparing it with similar coatings applied to
    wrought Ti&-6Al&-4V. The coatings were characterised using scanning
    electron microscopy and X-ray diffraction. For both Ti and Ti&-6Al&-4V
    alloys the use of amorphous B as a B element supplier in the boriding
    powder pack led to the formation of a uniform external boride layer,
    while the use of B4C as a B element supplier in the pack and
    under the same boronizing conditions, led to the formation of an
    external TiN layer and an internal layer containing B. The thermodynamic
    calculations performed proved successful in determining the appropriate
    conditions for boride coating deposition and estimating the phases
    likely to be formed. Finally the effect of surface roughness on the
    coating quality is discussed.