Comparative Analysis of Mechanical Properties of WC-based Cermet Coatings Sprayed by HVOF onto AZ31 Magnesium Alloy Substrates
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1
Department of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego St. 18a, 44-100 Gliwice, Poland
2
Department of Metal Forming, Welding and Metrology, Faculty of Mechanical Engineering, Wroclaw University of Science and Technology, Łukasiewicza St. 5, 50-371 Wroclaw, Poland
Publication date: 2021-06-01
Corresponding author
Ewa Jonda
Department of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego St. 18a, 44-100 Gliwice, Poland
Adv. Sci. Technol. Res. J. 2021; 15(2):57-64
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ABSTRACT
Magnesium alloys are very interesting engineering materials due to their very high
strength to density ratio (the best among metallic alloys). However, because of low hardness
as well as low resistance against erosion, abrasion and corrosion, their applications in the
industry is very limited. In order to improve mechanical performances, deposition of
hardening coating by thermal spraying was proposed. In this work, the WC-based coatings
with different binder (Co or Ni) and co-hardening additives (Cr or Cr3C2) manufactured by high
velocity oxy-fuel (HVOF) were studied. These coatings were deposited onto AZ31 magnesium
alloy. The crucial problem is obtaining good-adhered coating without damage the substrate,
because of relatively low temperature resistance of magnesium alloys (about 300 °C). To solve
this problem, HVOF method, which is low temperature and high velocity, was proposed. Also
an important role plays process parameters (e.g. spray distance, fuel medium, type of nozzle).
The goal of the study was to compare three types of cermet coatings manufactured from
commercially available powders (WC-Co, WC-Co-Cr and WC-Cr3C2-Ni) in terms of their
microstructure features, microhardness, instrumented indentation and fracture toughness.
Results revealed that selected process parameters made it possible to obtain well-adhered
coating with good fulfillment of the surface unevenness of the AZ31 substrate. The most
noticeable effect was influence of cobalt matrix on higher hardness (1.4 – 1.6 GPa) and Young
modulus (330 – 340 GPa) of deposited coatings in compare to the nickel matrix ones (1.2 GPa
and 305 GPa, respectively). The same trend was observed in case of fracture toughness, c.a.
6.5 MPa·m1/2 for Co-matrix and 4.9 MPa·m1/2 for Ni-matrix