Deposition of electroless (EL) Ni-B-Si 3N 4 composite coating and its characteristic properties are addressed.Hydrogen evolution limits the level of incorporation of Si 3N 4 particles in the EL Ni-B matrix to 2 wt%. Incorporation Si 3N 4 particles increased the surface roughness of the matrix but did not influence its structure. The microhardness of EL Ni-B-Si 3N 4 composite coating in its as-plated condition is 632 ± 17 HV0. 1. Heat treatment at 350 and 450°C for 1 h increased its hardness. Adhesive wear is the predominant wear mechanism of EL Ni-B-Si 3N 4 composite coating. Its corrosion protective ability did not differ much with its plain counterpart. © 2012 Copyright Taylor and Francis Group, LLC.

Suresh Krishnamoorthy Seshadri

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Electroless Ni-B-Si3N4 Composite Coating: Deposition and Evaluation of Its Characteristic Properties

Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry

The wear resistance of electrodeposited (ED) Ni-B and Ni-B-Si 3N4 composite coatings is compared. The effect of incorporation of Si3N4 particles in the ED Ni-B matrix on the surface morphology, structural characteristics and microhardness has been evaluated to correlate the wear resistance. The wear mechanism of ED Ni-B and Ni-B-Si3N4 composite coatings appears to be similar; both involve intensive plastic deformation of the coating due to the ploughing action of the hard counter disc. However, the extent of wear damage is relatively small for ED Ni-B-Si3N4 composite coatings. © 2008 Springer Science+Business Media, LLC.

Journal of Materials Science

Wear resistance of electrodeposited Ni-B and Ni-B-Si3N 4 composite coatings

Corrosion resistance of electrodeposited (ED) and electroless (EL) composite coatings have been a debatable issue in the published literature. The present paper aims to compare the corrosion resistance of ED Ni-B-Si3N4 composite coating with its plain counter part. The ED Ni-B coatings were prepared using Watt's nickel bath modified with the addition of dimethylamine borane and the ED Ni-B-Si3N4 composite coatings were prepared using the same bath in which Si3N4 particles (mean diameter: 0.80 μm) were dispersed in it. The structural and morphological characteristics of ED Ni-B and Ni-B-Si3N4 composite coatings were determined using X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM). The corrosion resistances of ED Ni-B and Ni-B-Si3N4 composite coatings, both in as-plated and heat treated conditions, in 3.5% NaCl, were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies. The study reveals that the extent of shift in corrosion potential (Ecorr) towards the noble direction, decrease in corrosion current density (icorr), increase in charge transfer resistance (Rct) and decrease in double layer capacitance (Cdl) values with the incorporation of Si3N4 particles in the ED Ni-B matrix is not appreciable, both in as-plated and heat-treated conditions. The occurrence of the second phase angle maximum suggests penetration of the electrolyte via the pores/micro-pores in these coating to create another interface, namely, the electrolyte/substrate. Unlike the nanosized particles, the micron size Si3N4 particles (mean diameter: 0.80 μm) used in this study is not capable of completely filling all the pores in the coating and allowed diffusion of chloride ions along the interface. The marginal improvement in corrosion resistance observed for ED Ni-B-Si3N4 composite coatings compared to its plain counterpart could have resulted from the decrease in effective metallic area prone to corrosion. © 2009 Elsevier B.V. All rights reserved.

Journal of Alloys and Compounds

Corrosion resistance of electrodeposited Ni-B and Ni-B-Si3N4 composite coatings

The preparation of Ni-B-Si3N4 composite coatings by electrodeposition technique and evaluation of their characteristic properties are addressed in this paper. The Ni-B-Si3N4 composite coatings were electrodeposited using a dimethylamine borane (DMAB)-modified Watt's nickel bath containing Si3N4 particles dispersed in it. The effect of chemical composition, structural and morphological characteristics, and hardness of electrodeposited (ED) Ni-B-Si3N4 composite coatings were evaluated and compared with that of ED Ni-B coatings. The study reveals that Si3N4 particles can be successfully codeposited in the ED Ni-B matrix. The maximum level of incorporation of Si3N4 particles, about 8 wt.%, is obtained at a bath loading of 50 g/l and at 1 A/dm2. The incorporation of Si3N4 particles decreases the metallic lustre, increases the surface roughness and alters the chemical composition of the ED Ni-B matrix. The average surface roughness of the ED Ni-B-Si3N4 composite coatings is 1.17 μm. The coating contains 89.6 wt.% Ni, 2.4 wt.% B and 8 wt.% Si3N4. The surface morphology of the coating reveals uniform distribution of Si3N4 particles in the ED Ni-B matrix. Incorporation of Si3N4 particles in the ED Ni-B matrix causes a change in crystal orientation. Heat treatment (400 °C for 1 h) increases the crystallinity and enables the formation of Ni3B phase. The Ni (1 1 1) texture is retained even after heat treatment at 400 °C for 1 h. The grain size of the coating is 6-8 nm in as-plated condition and it increases to 12-14 nm after heat treatment at 400 °C for 1 h. The microhardness of as-plated ED Ni-B-Si3N4 composite coating is 640 HV0.1 and it increases to 955 HV0.1 when the coating is heat treated at 400 °C for 1 h. © 2007 Elsevier B.V. All rights reserved.

Electrodeposited Ni-B-Si3N4 composite coating: Preparation and evaluation of its characteristic properties

This paper addresses the structural characteristics and phase transformation behaviour of plain electroless Ni-P coating and electroless Ni-P-Si3N4, Ni-P-CeO2 and Ni-P-TiO2 composite coatings. The X-ray diffraction patterns of electroless Ni-P-Si 3N4, Ni-P-CeO2 and Ni-P-TiO2 composite coatings are very similar to that of plain electroless Ni-P coating, both in as plated and heat-treated conditions. Selected area electron diffraction (SAED) patterns obtained on the Ni-P matrix of Ni-P-Si 3N4, Ni-P-CeO2 and Ni-P-TiO2 composite coatings exhibit diffuse ring patterns resembling the one obtained for plain electroless Ni-P coating. Phase transformation behaviour studied by differential scanning calorimetry (DSC) indicates that the variation in crystallization temperature and the energy evolved during crystallization of plain electroless Ni-P coating and electroless Ni-P-Si3N 4, Ni-P-CeO2 and Ni-P-TiO2 composite coatings is not significant. The study concludes that incorporation of Si 3N4, CeO2 and TiO2 particles in the Ni-P matrix does not have any influence on the structure and phase transformation behaviour of electroless Ni-P coatings. © 2005 Elsevier Ltd. All rights reserved.

Materials Research Bulletin

Structure and phase transformation behaviour of electroless Ni-P composite coatings

The present work aims to study the hardness and wear resistance of electroless Ni-B coatings. An alkaline bath having nickel chloride as the source of nickel and borohydride as the reducing agent was used to prepare the electroless Ni-B coatings. The structure, microhardness and wear resistance of electroless Ni-B coatings, both in as-plated and heat-treated conditions, were evaluated using X-ray diffraction (XRD), Leitz microhardness tester and a pin-on-disc wear test apparatus. XRD patterns reveal that electroless Ni-B coatings are amorphous in as-plated condition and undergo phase transformation to crystalline nickel and nickel borides upon heat-treatment. The microhardness of the electroless Ni-B coatings increases with increase in heat-treatment temperature and exhibit two maxima in the hardness vs. heat-treatment temperature curve. The specific wear rate increases with increase in applied load from 20 to 40 N and at all applied loads, the specific wear rate and coefficient of friction are less for heat-treated electroless Ni-B deposits compared to that obtained for as-plated ones. The wear process of electroless Ni-B coatings is governed by an adhesive wear mechanism. © 2004 Elsevier B.V. All rights reserved.

Journal	Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry
ISSN	15533174
Open Access	No