The present work pertains to the study of electroless Ni-P and Ni-P-Si3N4 composite coatings. The deposits are obtained from a proprietary high phosphorus electroless nickel plating bath, comprising nickel sulphate, sodium hypophosphite, complexing agents and stabilizers. The maximum weight percent of Si3N4 incorporated in the electroless deposits is obtained at a concentration of 10 g/l in the bath. The electroless Ni-P deposits have 0%, 2.01%, 5.81% and 8.10% of Si3N4, respectively, obtained from baths containing 0, 2, 5 and 10 g/l of Si3N4, are characterized by optical microscopy, XRD and TEM. Hardness is found to increase with the incorporation of Si3N4 at all heat treatment temperatures studied. Also hardness increases with an increase in weight percent of Si3N4 incorporated in the deposit. The analyses of the composite coatings by XRD and TEM reveal that the inclusion of Si3N4 particles does not change the amorphous nature of the Ni-P matrix.

Suresh Krishnamoorthy Seshadri

Electroless plating

Hardness

Heat treatment

Nickel compounds

Nickel plating

Optical microscopy

Silicon nitride

Sodium compounds

Stabilizers (agents)

Transmission electron microscopy

X ray diffraction analysis

Composite coatings

Protective coatings

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IIT Madras

Preparation and Characterization of Electroless Ni-P and Ni-P-Si3N4 Composite Coatings

Transactions of the Institute of Metal Finishing

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. © 2013 Elsevier B.V. All rights reserved.

Fulltext

Journal of Alloys and Compounds

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

The formation of electrodeposited Ni-B alloy coatings using a dimethylamine borane (DMAB) modified Watt's nickel bath and evaluation of their structural characteristics, hardness and wear resistance are discussed. The boron content in the electrodeposited Ni-B alloy coating is determined by the ratio of rate of reduction of nickel and rate of decomposition of DMAB. The boron content of the electrodeposited Ni-B coating decreases as the current density increased from 0.4 to 4 A dm-2. XRD diffraction pattern of electrodeposited Ni-B coatings in their as-plated condition exhibits the presence of Ni (1 1 1), (2 0 0) and (2 2 0) reflections with (1 1 1) texture. Heat treatment at 400 °C for 1 h has resulted in the formation of nickel boride phases, which results in an increase in hardness and wear resistance. The mechanism of wear in electrodeposited Ni-B coatings is intensive plastic deformation of the coating due to the ploughing action of the hard counter disk. © 2005 Elsevier B.V. All rights reserved.

Materials Chemistry and Physics

Electrodeposited Ni-B coatings: Formation and evaluation of hardness and wear resistance

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.

Journal of Applied Electrochemistry

Electroless Ni-P composite coatings

The present work deals with the formation of Ni-P/Ni-B duplex coatings by electroless plating process and evaluation of their hardness, wear resistance and corrosion resistance. The Ni-P/Ni-B duplex coatings were prepared using dual baths (acidic hypophosphite- and alkaline borohydride-reduced electroless nickel baths) with both Ni-P and Ni-B as inner layers and with varying single layer thickness. Scanning electron microscopy (SEM) was used to assess the duplex interface. The microhardness, wear resistance and corrosion resistance of electroless nickel duplex coatings were compared with electroless Ni-P and Ni-B coatings of similar thickness. The study reveals that the Ni-P and Ni-B coatings are amorphous in their as-plated condition and upon heat-treatment at 450 °C for 1h, both Ni-P and Ni-B coatings crystallize and produce nickel, nickel phosphide and nickel borides in the respective coatings. All the three phases are formed when Ni-P/Ni-B and Ni-B/Ni-P duplex coatings are heat-treated at 450 °C for 1h. The duplex coatings are uniform and the compatibility between the layers is good. The microhardness, wear resistance and corrosion resistance of the duplex coating is higher than Ni-P and Ni-B coatings of similar thickness. Among the two types of duplex coatings studied, hardness and wear resistance is higher for coatings having Ni-B coating as the outer layer whereas better corrosion resistance is offered by coatings having Ni-P coating as the outer layer. © 2003 Elsevier B.V. All rights reserved.

Electroless Ni-P/Ni-B duplex coatings: Preparation and evaluation of microhardness, wear and corrosion resistance

Electroless Nickel Plating

Chemistry of Electroless Plating

Transactions of the IMF

Effect of Cationic Surfactant on Deposition Behaviour in Electroless Ni-P-PTFE Composite Plating

The wear characteristics of Ni-P-SiC composite coatings

Evaluation Practice

10.1016/s0886-1633(89)80005-4

Thin Solid Films

Structural changes induced by heating in electroless nickel-phosphorus alloys

Preparation and characterization of electroless Ni-P and Ni-P-Si3N4 composite coatings

Journal	Transactions of the Institute of Metal Finishing
Publisher	Inst of Metal Finishing, Birmingham
ISSN	00202967
Open Access	No