Recent literature on the electrodeposition of metallic coatings containing nanosized particles is surveyed. The nanosized particles, suspended in the electrolyte by agitation and/or use of surfactants, can be codeposited with the metal. The inclusion of nanosized particles can give (i) an increased microhardness and corrosion resistance, (ii) modified growth to form a nanocrystalline metal deposit and (iii) a shift in the reduction potential of a metal ion. Many operating parameters influence the quantity of incorporated particles, including current density, bath agitation (or movement of work piece) and electrolyte composition. High incorporation rates of the dispersed particles have been achieved using (i) a high nanoparticle concentration in the electrolyte solution, (ii) smaller sized nanoparticles; (iii) a low concentration of electroactive species, (iv) ultrasonication during deposition and (v) pulsed current techniques. Compositional gradient coatings are possible having a controlled distribution of particles in the metal deposit and the theoretical models used to describe the phenomenon of particle codeposition within a metal deposit are critically considered.

Electrodeposition of composite coatings containing nanoparticles in a metal deposit

Over the last 40 years, the commercial production of titanium and its alloys has increased steadily. Whilst these materials have some very attractive properties, enabling applications in many industries, they are seldom used in mechanical engineering applications because of their poor tribological properties. This paper starts with an introduction to the titanium material and a review of the different types of surface treatment. The processes of nitriding, oxidation and carburizing are among the most popular thermochemical treatments aiming at improving the surface properties of Ti-alloys. Different kinds of nitriding are investigated like plasma nitriding, ion nitriding, and laser and gas nitriding. The kinetics of nitriding and the conditions for the formation of nitrided layers are studied. The influence of the main processing parameters such as temperature, time on the microstructure and the formation of new phases during the processes of nitriding is discussed. Also based on investigations presented in the literature, the effects of nitriding on the microhardness and the corrosion resistance of titanium and titanium alloys are analyzed. The improved mechanical properties, which arise from these thermochemical treatments, are discussed in relation to the potential for applying these alloys to different industries.

Enhancing the microstructure and properties of titanium alloys through nitriding and other surface engineering methods

Stainless steel, Co-Cr and Ni-Cr alloys have played an important role in many industrial sectors to combat environmental degradation. However, low hardness and poor wear properties have impeded their tribological and tribochemical applications. Conventional thermochemical treatments can be used to significantly harden these passive alloys but at the expense of their corrosion resistance due to precipitation induced depletion of Cr in the matrix. Research in 1980s led to the discovery of a new expanded austenite phase, i.e. so called S-phase with combined improvement in wear and corrosion resistance. Recent research has revealed that S-phase can be formed not only in stainless steels but also in Co-Cr alloys and Ni-Cr alloys. It is the purpose of this paper to critically review the S-phase surface engineering of stainless steels, Co-Cr alloys and Ni-Cr alloys. Particular attention will be paid to the structure, formation conditions, supersaturation, hardening mechanisms and metastability of...

S-phase surface engineering of Fe-Cr, Co-Cr and Ni-Cr alloys

Mechanical properties and wear and corrosion resistance of electrodeposited Ni-Co/SiC nanocomposite coating

The wear behaviour of electro-codeposited Ni–SiC composites

Martensitic grade stainless steel AISI 420 was nitrided in a low-pressure RF plasma using pure nitrogen. With a treatment time of 4.0 h at 400 °C, the nitrogen-rich layer on the sample was 20 μm thick and had a hardness of approximately 4.3 times higher than that of untreated material. The layer thickness was much greater than that obtained on AISI 304 under identical conditions, reflecting the different Cr content of the two alloys. Below the temperature at which CrN forms, the treated layer retains its martensitic structure, but with a larger lattice parameter than the bulk, a phase that can be termed ‘expanded martensite’, by analogy with the situation with austenitic stainless steel. Kinetics of the layer formation was also investigated which yielded an activation energy of 33.4 kJ/mol.

Characteristics of martensitic stainless steel nitrided in a low-pressure RF plasma

Composite plating is a method of co-depositing fine particles of metallic, non-metallic compound or polymers in the plated layer to improve material properties, such as wear-resistance, lubrication, or corrosion resistance. Bilayer Ni–SiC composite coatings were produced in this research on the base of a reported study. Before producing bilayer Ni–SiC composite coatings, effects of the particle size, the particle content, the pH of the electrolyte, the temperature, the current density, the stirring rate on the amount of SiC deposited in the Ni layer were investigated. By manipulating the current density and the plating time properly, bilayer Ni–SiC composite coatings were produced and mechanical properties of these coatings were evaluated by micro-indentation hardness tests.

Formation of bilayer Ni–SiC composite coatings by electrodeposition

Corrosion behavior of TiN, TiAlN, TiAlSiN thin films deposited on tool steel in the 3.5 wt.% NaCl solution

Deposition of tantalum nitride thin films by D.C. magnetron sputtering

Thin films of TiAlSiN were deposited on AISI H13 tool steel substrate using Ti and AlSi cathodes by a cathodic arc plasma deposition system. The influence of the nitrogen pressure, AlSi cathode arc current, bias voltage, and deposition temperature on the mechanical and the structural properties of the films were investigated. The hardness of the film decreased with the increase of nitrogen gas pressure. The hardness of the film increased with the increase of AlSi cathode arc current and the bias voltage. The hardness of the film reached 48 GPa at the deposition temperature of 300 °C and decreased with a further increase of the temperature. Wear and scratch tests were performed on thin films deposited in various conditions. The critical load of the films was above 50 N.

Sun Kyu Kim

Papers

Characteristics of martensitic stainless steel nitrided in a low-pressure RF plasma

Formation of bilayer Ni–SiC composite coatings by electrodeposition

Corrosion behavior of TiN, TiAlN, TiAlSiN thin films deposited on tool steel in the 3.5 wt.% NaCl solution

Deposition of tantalum nitride thin films by D.C. magnetron sputtering

Deposition of superhard TiAlSiN thin films by cathodic arc plasma deposition