A study on the wear resistance of electroless Ni–P/Diamond composite coatings

Electroless nickel, alloy, composite and nano coatings – A critical review

Abstract: The development of metal deposition processes based on electroless nickel, alloy and composite coatings on various surfaces has witnessed a surge in interest among researchers, with many recent applications made possible from many excellent properties. In recent years, these coatings have shown promising corrosion and wear resistance properties and large number of newer developments became most important from macro to nano level applications. After a brief review of the fundamental aspects underlying the coating processes, this paper discusses in detail about different electroless nickel alloy, composite, nano plating, bath techniques, preparation, characterization, new depositing mechanism and their recent applications, including brief notes on difficult substrate and waste treatment for green environment. Emphasis will be onto their recent progress, which will be discussed in detail and critically reviewed.

Electroless Ni-P composite coatings

Abstract: This review outlines the development of electroless Ni–P composite coatings. It highlights the method of formation, mechanism of particle incorporation, factors influencing particle incorporation, effect of particle incorporation on the structure, hardness, friction, wear and abrasion resistance, corrosion resistance, high temperature oxidation resistance of electroless Ni–P composite coatings as well as their applications. The improvement in surface properties offered by such composite coatings will have a significant impact on numerous industrial applications and in the future they will secure a more prominent place in the surface engineering of metals and alloys.

The physical and chemical properties of electroless nickel–phosphorus alloys and low reflectance nickel–phosphorus black surfaces

Abstract: Novel insights into the manufacture of nickel–phosphorus black surfaces by chemical etching of electroless-deposited Ni–P alloy has been achieved by examining the influence of pre-etch phosphorus composition and etching method on the resulting morphology, composition and reflectance of the black surface produced. An optimum phosphorus composition and etching regime to produce low reflectance blacks of 0.4% or lower in the visible region is proposed. Cross-sectional analysis of the etched surface has allowed, for the first time, an accurate determination of the scale of the enhanced morphologies produced and the thickness of the oxidised black layer itself. AFM studies have also provided information on the phase structure of the as-deposited Ni–P alloy.

Corrosion behavior of electroless Ni–P alloy coatings containing tungsten or nano-scattered alumina composite in 3.5% NaCl solution

Abstract: The corrosion protection performance of electroless deposited nickel–phosphorus (Ni–P) alloy coatings containing tungsten (Ni–P–W) or nano-scattered alumina (Ni–P–Al 2 O 3 ) composite coatings on low carbon steel was studied. The effect of heat treatment on the coating performance was also studied. The optimum conditions under which such coatings can provide good corrosion protection to the substrate were determined after two weeks of immersion in 3.5% NaCl solution. Electrochemical impedance spectroscopy (EIS) and polarization measurements have been used to evaluate the coating performance before and after heat treatment. The Ni–P–W coatings showed the highest surface resistance compared with Ni–P–Al 2 O 3 and Ni–P. The surface resistance of Ni–P–W coatings was 12.0 × 10 4 Ω cm 2 which is about the double of the resistance showed by Ni–P–Al 2 O 3 (7.00 × 10 4 Ω cm 2 ) and twenty times greater than the surface resistance of Ni–P (0.78 × 10 4 Ω cm 2 ). XRD analysis of non-heat-treated samples revealed formation of a protective tungsten phosphide phase. Heat treatment has an adverse effect on the corrosion protection performance of tungsten and alumina composite coatings. The surface resistance decreased sharply after heat treatment.

Synthesis and properties of electroless Ni–P–Nanometer Diamond composite coatings

Abstract: Nanometer Diamond (ND) was synthesized by using the detonation method. It was a kind of materials with properties of diamond and nanometer particle. The Ni–P–ND composite coating was prepared from a suspension of diamond nanoparticles in electroless bath. The tribological properties, hardness and corrosion behaviours of the composite coating on medium carbon steels were investigated. The Ni–P–ND composite coating exhibits not only high wear resistance but also low friction coefficient compared with the Ni–P composite coating. The highest microhardness of the Ni–P–ND composite coating was obtained by heat treated at 673 K. The corrosion resistance of Ni–P–ND composite coating is superior to that of Ni–P coating. The mechanisms of improvement of the tribological and electrochemical properties of the electroless composite coating are also discussed.

The measurement of wear resistance

Abstract: This is a discussion of several important aspects of evaluating wear resistance. It is focused on abrasion, which is a large area of the complex field of wear. There is no universal wear test. Instead it is necessary to analyze the factors that are most important in a given wear situation and to evaluate these separately or in simple combinations. Such evaluations or tests have the aim of making possible the wise selection of materials and the prediction of service performance. A good wear test should have demonstrated reliability (which is the same as reproducibility), ranking ability, and validity. The merit of these several qualities should be checked by statistical mathematics to avoid erroneous conclusions and misplaced confidence. Simplified statistical tests are provided here to facilitate such checking. This discussion is illustrated with data from a laboratory abrasion test that has a useful relation to ball mill wear. It is only one of several that apply to important areas of abrasive wear, but it illustrates a desirable approach to the problem of material selection.

Investigation of electroless Ni-P-SiC composite coatings

Abstract: Electroless Ni-P-SiC composite coatings were investigated from the viewpoint of bath formulation, technology and coating properties. A sound and homogeneous deposit containing 25-30 vol. percent SiC can be produced, using an optimum bath formulation and technology. In comparison with Ni-P coatings, Ni-P-SiC composite coatings possess greater hardness and higher porosity, as well as lower adhesion and corrosion resistance. It is a significant advantage that the wear resistance of the composite coating is considerably increased. Heat treatment at high temperature can improve adhesion and wearability of the composite coating. Structural analysis confirms that a new phase of Ni 3 Si compound exists in the Ni-P-SiC deposits annealed at 650 °C for 1 hr. In this paper, formation of the Ni 3 Si compound and wear mechanism of the coatings are discussed.

Structural Transformations in electroless Ni-P-B deposits

Abstract: Electroless Ni-P-B deposits with weight percentages of 0.72 P and 4.15 B; 1.87 P and 4.87 B, were observed to be a mixture of microcrystalline nickel and amorphous phases, based on X-ray diffraction and transmission electron microscopy. On annealing, Ni 3 P and Ni 3 B precipitated along with crystalline nickel in one step. The microhardness of the deposits showed typical precipitation hardening behavior, with hardness increasing from about 550 VHN in the as-deposited condition, to about 1000 VHN in the fully crystallized condition