**2.1. Categories of Co-deposition of particles**

#### *2.1.1. Co-deposition of wear-resistant particles*

Nano-diamond particles dispersed in Ni-Co matrix form good composite coating on AISI 1045 steel substrate [15]. This composite coating formed in a Watts-type bath using electrodeposition showed enhanced hardness coupled with excellent anti-wear performance and lower frictional coefficient. This was due to well-dispersed diamond particles in the Ni-Co matrix and better wetting and bonding ability between the nano-diamond particles and Ni-Co matrix.

Zn-ZrO2-SiC composite coating has been fabricated to improve the mechanical and thermal resilient properties of mild steel [16]. The surface properties imparted by this ternary- phase composite layer showed enhanced micro- hardness above 60% of the control sample. There was also minimal wear response ad abrasive deformation under the examined conditions.

Nano-particles of alumina (Al2O3) in nickel matrix have been found out to agglomerate [17, 18]. Agglomeration affects the amount and uniform distribution of co-deposited particles in the metal matrix. Hexadecylpridinium bromide (HPB) added as cation surfactant in the electro-deposition bath improved the quantity of Al2O3 particles co-deposited and also reduced particle agglomeration to achieve uniform distribution of Al2O3 particles in the nickel matrix. It was also found out that the wear resistance of the composite coatings increases as the concentration of the surfactant increases to a peak of 150 *ml* <sup>−</sup><sup>1</sup> after which a decreasing trend of wear resistance set in under -sliding and oil-lubricated conditions. This happened as a result of increased brittleness of metal matrix at peak of the surfactant concentration.

Composite coating can be classified on the basis of the matrix and the reinforcing co-deposited

**Types Chemical Compositions Concentrations**

*Nickel chloride: NiCl2 ⋅ 6H2O*

*Nickel chloride: NiCl2 ⋅ 6H2O*

*Nickel chloride: NiCl2 ⋅ 6H2O*

240*g* / *l* 20*g* / *l 30g / l*

300–450*g* / *l* 0–30*g* / *l* 30–45*g* / *l*

50–75*g* / *l* 100–130*g* / *l 50 – 55g/l*

*Boric acid: H3BO3*

*Boric acid: H3BO3*

*Boric acid: H3BO3*

**Watts Bath** *Nickel sulphate: NiSO4 ⋅ 7H2O*

**Sulphate Bath** *Nickel sulphamate: Ni(SO3 ⋅ N H2)2*

**Chloride Bath** *Nickel sulphate: NiSO4 ⋅ 7H2O*

The common metals used as matrices for electrolytic co-deposition are: Silver (Ag), Chromium

A variety of composite coatings can be deposited by reinforcing different nanoparticles. Reinforcement particles can be carbides (TiC, SiC, WC,Cr2C3)[2,3,4,5,6,7], borides [8], oxides (ZnO, In2O3, ZrO2, CeO2, Al2O3,Cr2O3,SiO2,TiO2) [9,10,11.12], graphite, diamond, or solid lubricants, such as polyethylene and polytetrafluoroethylene [13,14]. Variable amounts of these particles in the coatings become precipitated to impart special properties to the deposited layers. These properties mainly depend on the microstructure of the matrix phase of a composite coating and the amount and distribution of co-deposited particles (non-metallic

Nano-diamond particles dispersed in Ni-Co matrix form good composite coating on AISI 1045 steel substrate [15]. This composite coating formed in a Watts-type bath using electro-

(Cr), Cobalt (Co), Iron (Fe), Zinc (Zn), Nickel (Ni), Copper (Cu) and Gold (Au).

particles. The matrix phase on a broader scale can be grouped into:

inclusions) which are influenced by many process parameters.

**•** Metal matrix **•** Ceramic matrix **•** Polymer matrix

**Table 1.** Different types of electrolytic baths

44 Electrodeposition of Composite Materials

**2. Literature review**

**2.1. Categories of Co-deposition of particles**

*2.1.1. Co-deposition of wear-resistant particles*

Composite coating of Ni-P Al2O3 was formed on material of AISI 1045 steel disks by electroless deposition technique [19]. The second phase particles of Al2O3 in the Ni-P –based matrix evidenced well the output of hardness and wear resistance of the deposits. Heat treatment was carried out at intervals of 1 h across three consecutive temperature ranges of 200, 400 and 6000 C. The result showed that composite coating heattreated at 4000 C has maximum hardness and wear resistance.

With the aid of cetyltrimethylammonium bromide (CTAB) in a modified Watts bath, codeposit of Fe2O3 has been successfully dispersed in Ni-Co matrix [20] to form composite coatings of Ni-Co- Fe2O3. The results showed that co-deposition of Fe2O3 particles with Ni-Co matrix is favored at higher concentration and there is refinement of the crystallite of the composite deposit. The deposition of Co is favored at high concentration of CTAB.

The mechanical parts of machine under constant motion are subject to continuous friction, wear and tear. Nano- particles of Al2O3, TiO2, Si3N4 and diamond were consecutively dispersed onto nickel matrix to form composite coatings to study their tribological behaviors and wear mechanisms [21]. The SEM results of the composite samples revealed refine microstructures and enhanced micro-hardness compared with pure nickel coating. Only the Ni- Al2O3 and Nidiamond composite coatings showed improved tribological properties.

Nickel-based composite coating is the most popular wear-resistant composite coating used in abrasive tools, gear systems, chains assembly, measuring tools and gauges. Nickel matrix composites with various dispersed phases (Al2O3, SiO2, SiC, WC and diamond) are fabricated by electrolytic co-deposition from Nickel sulphamate and Watts electrolytes.

**Figure 3.** Vickers micro-hardness values for different ranges of particle size in a nickel deposit.
