Correlation between structure and properties of annealed electroless Ni-W-P coatings

H. Liu, H. L. Yao, G. E. Thompson, Z. Liu, G. Harrison

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Ni-W-P coatings with different structures were prepared by electroless deposition. The correlation between the coating structure before and after annealing with hardness and corrosion resistance has been examined by microhardness measurement, potentiodynamic polarisation and corrosion weight loss tests, and by quantitative X-ray diffraction technology and scanning electron microscopy observation of the corrosion morphology. The results indicate that incorporation of tungsten (4-5 wt-%) in Ni-P deposits does not change the amorphous structure of the Ni-11.3 P (wt-%) coating or the mixed structure of the Ni-6.8 P (wt-%) coating, but it changes the Ni-5.1 W-9.3 P (wt-%) coating into a critical amorphous structure. The coating with a critical amorphous structure develops a higher degree of crystallisation, larger crystal size and smaller number of Ni3P crystallites after annealing >300 degrees C. It also exhibits the highest peak hardness and the poorest corrosion resistance after annealing at 400 degrees C compared with the other two structural coatings (e.g. amorphous and mixed structures).
    Original languageEnglish
    Pages (from-to)412-419
    Number of pages7
    JournalSurface Engineering
    Volume31
    Issue number6
    DOIs
    Publication statusPublished - Jun 2015

    Keywords

    • Electroless; Structure; Microstrain; Hardness; Corrosion

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