MCrAlY(M=Ni, Co, or Ni-Co)coatings with good high temperature oxidation resistance have attracted great interest. They are widely used in gas turbines as protecting layers, such as thermal barrier coatings and seal coatings. Among many methods developed for preparing MCrAlY coatings, electroplating has drawn great attention due to its perfect bond strength, precise controllability, good coating ability for complex shape and so on. In this paper, the MCrAlY coatings have been prepared by a composite plating way. During this process, the CrAlY particles are wrapped with Ni clad layer. The thickness of the composite coatings is controlled at 150- 200 μm. The plating tests results indicate that the density of the clad layers mainly depend on the electroplating time. After that, these coatings are heat treated under the vacuum condition to make elements diffuse, forming homogeneous M(Ni)CrAlY component. The high-temperature oxidation resistance tests of the prepared coatings show good antioxidant ability at 1000 °C under air condition.

New concept and method of testing for the interconnecting porosity of thermally sprayed nonconductive ceramic coatings is proposed. This process is useful to differentiate the open porosity from the closed porosity. Thermally sprayed ceramic coating with metallic substrate is plated, and the intergranular gaps in the coating are filled by deposited metal. Typically, 304 stainless steel substrate deposited with atmospheric plasma sprayed alumina coating is immersed in copper(II) sulphate bath, and electroplated. Inward of the alumina coating, plating solution penetrates toward the interface of coating/substrate via interconnected porosity, and attains the coating-substrate interface to deposit metallic copper. Deposit of copper is gradually grown up along the coating intergranular. The exposure of deposited copper on the coating surface can be visible. Because these phenomena occur only in the interconnected pore structure, it is easy to differentiate the interconnected porosity from the closed porosity. Also the proposed process suggests the unprecedented possibility of manufacturing method of three-dimensional structure of thermally sprayed ceramic coating.

This paper presents a life cycle assessment comparison of electroplating and various thermal spray processes for the formation of nickel coatings. The comparison was carried out using a peer-reviewed database of upstream materials and energy and commercial LCA software. Material and energy use and the corresponding emissions of each coating process were converted to impact scores by means of the Eco-Indicator-99 method.

The implementation of magnesium alloys for automotive, aeronautic and other applications is of the great importance due to their especial properties. Magnesium offers greater weight saving capacity than aluminium, as its density, 1.7 g/cm -3 , is two thirds the density of aluminium, 2.7 g/cm -3 , without significant loss of strength and magnesium alloys show high specific strength. On the other hand surface properties of magnesium alloys like wear and corrosion resistance are rather poor. A large amount of methods are intensively elaborated to overcome this problem from developing of new alloys, different surface treatment methods and a great variety of coating systems. In present work the results concerning improvement of corrosion and wear resistance of magnesium alloys by means of zinc based coatings are presented. Coatings are deposited on magnesium substrates (AM20, AZ31, AZ91) by arc spraying with Zn, ZnAl4 and ZnAl15 solid wires as well as by electroplating of zinc. Nevertheless the onset of bimetallic corrosion between Zn and Mg significantly increases corrosion current density. In order to provide longer protection, two main technological solutions are taken into consideration. First relies upon a modification of the main electroplating technology, second is based on the selection of an effective post treatment. For the first approach a consecutive process is elaborated based on the two-step electrodeposition. The first is from alkaline bath followed by the second step in acidic chloride bath. A dense and compact complex layer is obtained. The second approach is based on the post treatment of deposited coatings and provides a formation of thick and uniform reaction layer in magnesium on the interface between zinc or zinc based coating and substrate. These layers have fine eutectic structure with microhardness 3-4 times higher than that of the base material. Heat treatment is carried out with focused irradiation of tungsten halogen lamp line heater in atmosphere. Microstructure of deposited coatings as well as that of modified surface layers is investigated by metallographic methods. Corrosion properties are estimated by electrochemical measurements. Abrasion wear resistance of the modified layers is determined by scratch test and oscillating wear tests. It is shown that the both applied methods improve corrosion properties of magnesium alloys. Electrolytic zinc coatings deposited by electroplating in the elaborated two- step process demonstrate good barrier properties. Durability increases about three times in comparison with a single coat obtained from alkaline bath. Infra red heat treatment of thermal spray coatings results in formation of modified layers in magnesium substrates that prevent the galvanic corrosion of investigated systems. Wear resistance of reaction layers is up to 4 times higher to compare with the base material.

Conventional decorative chrome plating operations are known to be environmentally and occupationally hazardous because of the use of hexavalent chromium and other toxic chemicals. An alternative ArcBright™ chrome technology has been developed to eliminate these hazards and simultaneously simplify manufacturing methods in this industry. The application method presented here uses an organic base coat and a physically vapor deposited (PVD) chrome to replace electroplated copper-nickel-chrome structure. An advanced rapid cycle, high rate PVD chrome coating method has been developed for this application to be able to increase throughput to the levels required in the automotive sector and to minimize application cost. The technology is applicable to many metals, plastics, composites and other solid materials that are not possible by conventional electroplating providing a wider choice of substrates. The PVD chrome process has been characterized and the ArcBright chrome has been qualified to automotive specifications.

High temperature oxidation behavior of MCrAlY coatings was studied at several temperatures in the range from 800 to 1100°C. In this study the MCrAlY coatings were obtained by plating using CrAlY as precursor powders in an electrolytic bath containing nickel and cobalt salt in solution. The size of the precursor CrAlY powders used was generally below 10 um. As-plated coatings consisted of a random distribution of CrAlY particles in the Ni-Co matrix. The heat-treatment of the as-plated coatings at elevated temperature resulted in the development of a gamma and beta structure. Both as-deposited and oxidized coatings were characterized by optical, scanning electron microscope and electron beam microprobe. During oxidation the coatings formed alumina scale with a negligible amount of transient nickel and chromium oxides. The spallation resistance of the oxide scale was investigated by thermal shock testing. The test consisted of a rapid cooling from 1000°C to 100°C with a two- minute dwell time at the maximum temperature. The thermal shock test was conducted in a) as–deposited and heat-treated condition and b) after preoxidation at 800°C and 1050°C, respectively. The coatings retained the alumina scale during thermal shock cycling.

MCrAlY bond coats were deposited on nickel base substrate by electroplated process. The bond coats were plated using ‘CrAlY’ precursor powders suspended in an electrolytic bath containing nickel and cobalt in solution. The CrAlY powders used had size in the range generally below 10 um. The as-deposited coatings were heat-treated in a vacuum at elevated temperature. The roughness of the as-deposited coatings was on the range from 2 to 4 um (average). Yttria stabilized zirconia thermal barrier coatings, 7YSZ were deposited by air plasma spray. The thickness of the both bond coats and TBCs was varied in order to determine the effects of thickness in the stability of the thermal barrier coatings. The coated samples were tested in a static furnace and also in a thermal shock test rig where the samples could be cooled rapidly from 1000°C to 100°C at a predetermined rate. The TGO formed at temperatures in the range from 800 to 1050°C was characterized by optical, scanning electron microscope and electron beam microprobe.