Electroless Ni-B coatings have found large applications due to their high hardness and wear resistance. The present paper tries to investigate the influence of coating process parameters on the microhardness of electroless Ni-B coating with the help of Taguchi analysis. Four parameters, namely, bath temperature, concentration of reducing agent, concentration of nickel source, and annealing temperature, are considered and fitted into an L27 orthogonal array to find out the optimized condition for improved hardness of the coating. The optimized condition is found to yield about 19% improvement in hardness of the coating compared to the initial condition. The significance of the process parameters and their interactions on the hardness of Ni-B coating is studied with the help of analysis of variance, which revealed that annealing temperature and concentration of reducing agent have significant influence over the hardness characteristics of electroless Ni-B coating. The compositional, microstructural, and pha...

Influence of Process Parameters on Microhardness of Electroless Ni-B Coatings:

Nickel–ceramic microfiltration membranes were prepared by electroless deposition of nickel on the activated ceramic membrane substrates having a nominal pore size of 275 nm. Two different surfactants, namely sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB), were studied for their ability to alter the performance characteristics of plating baths as well as composite membranes. Parameters evaluated include the bath conversion, plating efficiency, metal film thickness, average pore size of the composite membranes and per cent pore densification. The overall plating rate was found to increase up to 32% with the addition of SDS and 45% with the addition of CTAB. Addition of surfactants not only resulted in increased film thickness (4–5 μm) but also accounted for considerable reduction in average pore size of the composite membrane. CTAB was found to be more effective and efficient than SDS for nickel membrane fabrication.

Effect of surfactants on performance of electroless plating baths for nickel-ceramic composite membrane fabrication

In the metal plating industry, nickel and gold plating baths are used, which contain toxic materials and cause wastewater problems. Despite these disadvantages, there is a strong need for both these types of metal plating because of their aesthetic properties. However, until now, nickel plating has not been used in conjunction with gold plating because nickel plating baths contain sulphates. In this study, gold plating on a nickel plated surface is investigated using baths containing acetylacetonate salts. The physical parameters of the plated materials, which were favourable, were determined by hydrogen embrittlement tests, visible region spectrophotometry and the Charpy impact test.

Development of alternative environment friendly nickel and gold plating baths

Electroless Ni–B deposits have found many applications because of their unique properties. To enhance the performance of Ni–B deposit, one can add a third element and accordingly Ni–Ba–B ternary alloy synthesized and characterized for the first time. The alloy deposits of Ni–Ba–B on steel substrate are characterized for their chemical composition, microstructures, morphology, and micro-hardness by means of different instrumental techniques. Microstructural examination by FE-SEM indicated that the grains of coatings are in the form of nodule with different microstructures. The XRD experiments confirmed the simultaneous presence of amorphous and microcrystalline phases in the Ni–Ba–B deposits. Compared to Ni–B deposits, the micro-hardness and corrosion resistance of the ternary deposits are also improved.

Impact of Barium in Improving Corrosion Resistance and Properties of Electroless Ni–Ba–B Alloy Deposits

In this paper, a surface roughness (SR) study on the powder mixed electrical discharge machining of EN8 steel has been carried out. Response surface methodology has been used to plan and analyse the experiments. Average current, pulse on time, diameter of electrode and concentration of chromium powder added into the dielectric fluid of electrical discharge machining were chosen as process parameters to study the powder mixed electrical discharge machining performance in terms of SR. Experiments have been performed on a newly designed experimental set-up developed in the laboratory. An empirical model has been developed for SR. In addition, the recommended model has been verified by conducting confirmation experiments.

Effect of chromium powder suspended dielectric on surface roughness in PMEDM process

Despite having some useful properties, stainless steels suffer from lack of suitable surface hardness. In this research electroless Ni–B–Tl coating was used with the aim to increase their surface hardness. The effects of nickel chloride, sodium borohydride, thallium nitrate and ethylenediamine on chemical composition of coating were studied. To achieve an increase in hardness, the effects of heat treatment on the hardness of the deposited layer at various temperatures were also studied. The results showed that the deposition rate and surface hardness of the deposited layer are affected by the variation in concentration of bath components. The microstructure of the electroless Ni–B–Tl coating consists of nickel and super saturated solid solutions. It was also found that the hardness of the coating was increased due to the formation of Ni2B and Ni3B phases during heat treatment.

R. A. Khosroshahi

Papers

Study of chemical composition and heat treatment of electroless Ni–B–Tl alloy coating on AISI 316 stainless steel