In coal fired power plants, the metallic surfaces such as boiler tubes, walls of combustion chambers and other parts degrade by corrosion, erosion and abrasion. It happens due to the hot gaseous environment, steam oxidation and presence of hard minerals and impurities in the coal. It is very important to protect these surfaces from material loss, otherwise it would lead to increased repair and maintenance cost along with decreased plant efficiency. In this paper, the role of thermal spray coatings has been studied for the protection of different steel grades exposed to such degrading conditions at high temperatures, in coal-based power plants. A comprehensive study has been done by analysing and comparing the work done by various researchers. Some recent advancements related to coating materials and modification in coating techniques have also been studied. This paper would be helpful for the researchers to get an idea for selecting an appropriate substrate material and coating material for industrial applications.

The sliding wear of hot and cold spray nickel-alumina coatings on SA 213-T 91 boiler steel has been evaluated and compared. The investigation was conducted with pin-on-disc apparatus. The wear testing was done by varying normal loads of 30, 40, and 50N at a constant sliding velocity of 1 ms-1. Then another set of experimentation was done at different sliding velocities of 0.5, 1, and 2 ms-1 at a constant normal load of 30 N. This experimentation was designed to study the effect of varying normal loads and sliding velocities on the wear performance of coatings developed with hot and cold spray techniques. The variation of friction coefficient and wear rate with variation in normal loads and sliding velocities were plotted and analyzed. The evaluation of wear mechanisms and characteristics of Ni-Al2O3 coatings is done with the help of weight change measurements and FE-SEM analysis. The wear resistance of hot spray coatings was found better at high normal loads and sliding velocities in comparison to cold sprayed coatings.

There is an excessive material loss in steels components due to sliding wear in different industrial applications. The SS 316 steel is extensively used in the power generation industry for boilers, induction fans, ducts, etc., and counter high sliding wear. The studies have shown that protective coatings deposited by thermal spray methods are successful in controlling the wear and enhancing the service life of steels. In this work, the nickel-alumina coating was deposited on SS 316 by cold spray technique to understand the effectiveness of coatings to resist wear. The wear behavior of coatings was analyzed by conducting the wear test on a pin-on-disc apparatus at different loads, i.e., 30, 40 and 50 N keeping the speed constant. The wear trends and variation in friction coefficient due to wear were observed. The mechanical and microstructural characterization was done by FE-SEM/EDS and XRD techniques. The coatings were found effective in resisting the wear on SS 316 steel. The results indicate that the wear rate of coatings increased with an increase in normal load.

There is an increased awareness to preserve the environment in the present day society. Rice Husk (RH),is the widely available agricultural wastes and is a serious concern for the environment. It is a potential material for use as alternative material in the construction and insulation industry. The particle board made from rice husk (RH) or rice husk ash (RHA), bonded by resin under the application of pressure and temperature. Urea formaldehyde is the organic resin used in general for interior use whereas phenol formaldehyde for external disclosure. The said resins are preferred for their water-resistant properties and better binding strength. The present study investigates the potential of rice husk reinforced boards by experimenting the different compositions and thicknesses. The objective is to perform a thermal analysis of the processed Rice husk boards. Boards made from rice husk are biodegradable unlike glass wool & other synthetic insulations. After experimenting on different fabrication conditions, six samples were finalized and were tested for physical and thermal viability in their applications. This study found that by adding ash of rice husk, the density of board decreases with respect to the board of same weight and consisting of rice husk only. Moisture Content is higher in case of boards with RHA but is within permissible limits. RHA reinforced boards have improved thermal properties, which is desirable in case of insulation boards.