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Over the years, the world has been in the look out of novel materials and technologies that would lead to a better one tomorrow. Scientists, Technologists, Academicians have been working together to meet this objective. Surface Coating or Surface Deposition is not an uncommon technique while one desires to enhance the characteristics of the surface. Moreover, the thickness, orientation, growth kinetics, and adherence of the coating can be regulated through monitoring the parameters like Temperature, time, ambiance, and the nature of the substrate. The present paper critically discusses one of the surface coating technologies known as boronizing. The two steel substrates were so chosen that they differ wide in their characteristics. After boronizing, the case depth, microhardness distribution, and microstructural analysis were done on the coated substrates. The results were compared against each other. Conclusions were drawn on the basis of results obtained.Macrokinetics Of Plasma Electrolytic Oxidation Of Az91d Alloy
Plasma Electrolytic Oxidation (PEO) produces thick oxide layer on the surface of metals and alloys. If the process is performed in AC mode, two levels of kinetics can be defined. On one hand, during each period of the alternating (50-60 Hz) current cathodic and anodic processes are repeated. The kinetics of these processes can be referred to as the microkinetics. On the other hand, the treatment time for a typical specimen is 30-90 minutes and the kinetical behavior (macrokinetics) on that scale is completely different than the microkinetics. For many practical purposes, the macrokinetics of a PEO process is not only more ready for an experimental study, but also much more useful in the applicative sense. A macrokinetical study of the PEO treatment of AZ91D magnesium alloy is presented. Plausible explanations of the process are discussed and optimal process parameters are determined.Properties Of Powder Coating Formed By Gas-dynamic Accelerator
The paper presents the results of investigating the properties of metal and ceramic coatings deposited on the steel or the aluminium substrates by using a multi-chamber gas-dynamic accelerator. Coatings made of the Al2O3 powder are widely applied to protect surfaces of parts operating in aggressive environments and at high temperatures. The multi-chamber gas-dynamic accelerator (MCDS) has replaceable nozzles and operates with a fuel mixture of low-pressure gases – propane (30 %) + butane (70 %) – oxygen – air. The velocity of the frontal area of the cloud of the Al2O3 powder with particle sizes of 5.6 – 22.5 microns at a nozzle length of 500 mm is 1300 +/- 200 m/s. MCDS with a nozzle length of 500 mm provides the conditions for formation of a dense ceramic layer having hardness of 1320 +/-25 HV0.3 and porosity of less than 1 %. Productivity of the technology is 0.72 kg/h at a deposition efficiency - 0.65 %, flow rate of oxygen equal to 7.5 m3/h, and flow rate of propane + butane equal to 1.3 m3/h. High adhesion of the ceramic layer to the substrate is provided by the transition layer up to 15 microns thick. MCDS allows form Nano-crystalline coating of the titanium or nickel based alloy powders. The dense layer of lamellas and deformed particles of powder is formed on the sample surface. Lamellas consist of Nano-crystalline grains size of 30 – 100 nm. Scratch-test has shown that the coatings are plastic and have high adhesive and cohesive strength.