Metal-matrix composites mechanical coating

In recent years, there has been a growing interest in the electrochemical synthesis of composite materials consisting of metal matrix with embedded particles of oxides, carbides, borides, etc. Metal-matrix composites offer new possibilities in fabrication of ftmctional coatings with radically improved durability and performance [1], However, in spite of the efforts of many researches, the overall picture of the processes occurring during co-deposition of metal with dispersed phase and mechanism of particle-induced modification of mechanical and chemical properties still remain unclear. In this study, we focused on the kinetics and mechanism of the electrochemical co-deposition of nickel with highly dispersed oxide phases of different nature and morphology. 

Purely inorganic sol-gel silica coatings have also been used for mechanical protection of metals [51,54,55] and metal matrix composites [5,16,56]. The main disadvantage of purely inorganic vitreous Si02 coatings is their brittleness [33], and the use of multilayered systems is usually adopted. 

Research work conducted over many years [118-121] has demonstrate that through composite electrodeposition, significant improvements in the properties of the pure metal matrix can be achieved, including hardness, wear resistance, and corrosion behavior. In particular, the incorporation of ceramic or other hard particles is an effective way to improve coating hardness and wear resistance. Hardness increase can be explained according to the Orowan mechanism of dispersion hardening [122], as long as particle size is less than 1 pm [119]. This increase depends on the interparticle distance, i.e., on particle size and volume fraction of the hard phase. 

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