Development of Heat- and Wear-resisting Light Alloy Based Composite Produced by Applying Graded Thermal Spraying Technology

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Three types of thermal spraying processes were applied to fabricate an excellent heat- and wear-resisting magnesium alloy based composite. The spraying methods. experimentally assessed were conventional flame spraying, plasma spraying and high velocity oxgen/fuel (HVOF) flame spraying, respectively. Such cermet materials consisting of either system of NI-WC, WC-CO or Cr_3C_2-Co were sprayed on the surface of the magnesium alloy AZ31 substrate. Aluninum under coating was precedently applied before the cermet sprayings to enhance the bond strength between the cermet coatings and the substrate AZ31. Furthermore, diffusion heat treatment was introduced following the cermet sprayings to increase the adhesiveness of the coatings.The HVOF spraying gained the highest bond strength, density, hardness and wear resistance. Vickers hardness of the WC-12%Co cermet coating produced by the HVOF spraying reached to 800 - 1200. The alloy composite with the HVOF sprayed WC-12%Co cermet coating was superior above 20 times in abrasive wear resistance to hardened S45C steel. The HVOF spraying process allows to take place with little decarburization of the carbide phases and is expected to be applicable for fabrication of new excellent light alloy based composites.