**3. Electrolytic codepositon**

Codeposition of metals with ceramic particles is a new technique for obtaining hard, wear resistant coatings; therefore, its application to our daily life has not been studied in the engineering field enough. The deposition of two or more materials on a substrate simultane‐ ously is defined as "electrolytic codeposition" or "electrolytic composite coating". In this process, both materials (the matrix and the reinforcement) are subjected to the surface and the desired properties can be obtained in one step process easily. When considering the codepo‐ sition of Cr and SiC, the metal matrix (Cr) increases the hardness and the wear resistance of the material. Additionally, the reinforcement (SiC) improves corrosion behaviour and boosts both, the hardness and the wear resistance of the structure.

First examples of electro codeposited composite coatings are known to have been used for antislip stairs of marines which are Ni matrix sand (SiO2) particles. Fink and Prince investigated the self lubricant properties of Cu-Graphite electrolytic composites for car engine applications in 1928. At the beginning of the sixties, the interest in this specific topic was increased and researchers were focussed on the engineering applications of these specific coatings. Especial‐ ly, the interest in the application of Ni-SiC and Ni-PTFE in the automobile industry has grown significantly in the last decades.

From this perspective, codeposited composite coatings have excellent wear resistance and permit emergency dry-running of machinery. The following examples of practical utilisation illustrate the benefits of the mentioned coatings: Ni matrix coatings with 8-10% vol. of SiC are used to increase the life of internal combustion engine cylinder bores; composite coatings based on CrxCy (chromium carbide) in a Co matrix are used as wear resistant coatings in gas turbines. Cr deposits with Al2O3 inclusions are used in piston rings for diesel engines. Diamond embedded into a Ni matrix form the cutting edge in tools such as chainsaws, grinding discs or dental drills [1].

A number of scientists have investigated the mechanism of the electrodeposition of compo‐ sites. The mechanisms proposed by most of them include these steps [1]:


**Figure 1.** Zones in a coated material

60 Electrodeposition of Composite Materials

**3. Electrolytic codepositon**

significantly in the last decades.

or dental drills [1].

The rest of the zones and the properties affected are clarified in Section 3.2 because these zones

Codeposition of metals with ceramic particles is a new technique for obtaining hard, wear resistant coatings; therefore, its application to our daily life has not been studied in the engineering field enough. The deposition of two or more materials on a substrate simultane‐ ously is defined as "electrolytic codeposition" or "electrolytic composite coating". In this process, both materials (the matrix and the reinforcement) are subjected to the surface and the desired properties can be obtained in one step process easily. When considering the codepo‐ sition of Cr and SiC, the metal matrix (Cr) increases the hardness and the wear resistance of the material. Additionally, the reinforcement (SiC) improves corrosion behaviour and boosts

First examples of electro codeposited composite coatings are known to have been used for antislip stairs of marines which are Ni matrix sand (SiO2) particles. Fink and Prince investigated the self lubricant properties of Cu-Graphite electrolytic composites for car engine applications in 1928. At the beginning of the sixties, the interest in this specific topic was increased and researchers were focussed on the engineering applications of these specific coatings. Especial‐ ly, the interest in the application of Ni-SiC and Ni-PTFE in the automobile industry has grown

From this perspective, codeposited composite coatings have excellent wear resistance and permit emergency dry-running of machinery. The following examples of practical utilisation illustrate the benefits of the mentioned coatings: Ni matrix coatings with 8-10% vol. of SiC are used to increase the life of internal combustion engine cylinder bores; composite coatings based on CrxCy (chromium carbide) in a Co matrix are used as wear resistant coatings in gas turbines. Cr deposits with Al2O3 inclusions are used in piston rings for diesel engines. Diamond embedded into a Ni matrix form the cutting edge in tools such as chainsaws, grinding discs

are related to the coating itself and the interfaces between coating.

both, the hardness and the wear resistance of the structure.

There are a variety of models with a quantitative approach to the incorporation rate of the particles into the matrix; however the current and most widely-known one has been suggested by Roos et al. in 1990 [8].

Similarly, Wan-chang Sun et al. [9] described codeposition process for Ni-Al2O3 system in three steps. This is illustrated in Figure 2.

**Figure 2.** Schematic description of the three-step method of composite coating

These steps can be summerized for Ni-Al2O3/graphite system as follows:


#### **3.1. Effective parameters**

The factors affecting the coating structure, subsequently, the properties and the performance of the material were given in previous sections (see Section 2.1 and 2.2). This section focuses on the specification of these factors; besides, the additional ones, which belong to the codepo‐ sition process, are described, namely zeta potential, particle size, circulation of the suspension (particle additional electrolyte) which belong to the codeposition process.
