Room and high temperature wear behaviour of Ni matrix micro- and nano-SiC composite electrodeposits

In the frame of the research domain of the production of metal matrix composite deposits the aim of this work is the production of Ni matrix composite coatings containing either micro- or nano- SiC particles and their characterization. The electrodeposition has been carried out under DC conditions using a nickel sulfammate plating bath into which the particles were suspended. The composite coatings were tested and compared to pure nickel deposits regarding the microstructure, microhardness and wear resistance under high load at both room temperature and 300oC. The codeposition of the SiC particles changed the microstructure of the nickel matrix and the preferential orientation of the Ni grains leading to a noticeable improvement on both microhardness and wear resistance. The pure nickel deposit present a pseudocolumnar structure and a preferential [100] orientation. The codeposition of the μSiC particles slightly modified the dimensions and the orientation of the pseudocolumns and lead to a [110] preferential orientation of the Ni grains. The microstructural modifications and the presence of the SiC particles in the metal matrix lead to a 51% increase of the microhardness, a 63% decrease of the wear coefficient at 300oC while it did not offer any improvement at the wear resistance at room temperature. The codeposition of nSiC particles lead to a noticeable grain refinement and the loss of a preferential orientation. The microstructural modifications in this case lead to a 67% increase of the microhardness, a 70% decrease of the wear coefficient at room temperature and a 88% decrease of the wear coefficient at 300oC in comparison to the pure nickel deposits. The improved wear resistance of the Ni/nSiC deposits is attributed to their compact microstructure and to the absence of a preferential orientation which was maintained also after wearing, contrary to the other two types of deposits.