Fabrication and properties of TiB2-TiC reinforced NiAl coatings by reactive plasma spraying on AZ91D magnesium alloy

Abstract

TiB2-TiC ceramic reinforced in situ NiAl matrix composite coatings were fabricated on AZ91D magnesium alloy by reactive plasma spraying (RPS) from the mixtures of Ni-Al and self-propagating high-temperature synthesis product in a 10 wt%Ni-3Ti-B4C system. Microstructure and properties including bonding strength, microhardness and electrochemical corrosion and wear resistances for the RPS coatings were investigated. The results showed that the coatings were mainly composed of the desired phases of TiB2, TiC and NiAl, and exhibited the compacted and layered morphology. The RPS coatings bound tightly to the magnesium alloy due to the prior preparation of a thin electroless plating Ni-P layer on the substrate, with bonding strength as high as 24.2–34.6 MPa. The produced Ni-P/TiB2-TiC reinforced in situ NiAl matrix coatings provided good protection against both wear and corrosion for substrate. Wear resistance of the coatings increased with an increase in the content of TiB2-TiC in the in situ NiAl matrix, while the corrosion resistance displayed a decreasing trend.