The manufacturing of electro spark deposition machine to repair the surface defects in tool steels

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: The manufacturing of electro spark deposition machine to repair the surface defects in tool steels

ارائه دهنده: Provider: Shaghayegh Jaderian

اساتید راهنما: Supervisors: Dr. Mohsen Sheikhi, Dr. Yoosef Mazaheri Roudbari

اساتید مشاور: Advisory Professors: Dr. Mohammad Amin Ghasemi

اساتید ممتحن یا داور: Examining professors or referees: Dr. Shahab kazemi, Dr Meysam Noori

زمان و تاریخ ارائه: Time and date of presentation: 2022/09/10

مکان ارائه: Place of presentation: Engineering Faculty

چکیده: Abstract: Fixing, saving, and improving processes of industrial pieces surfaces have always been important, among them, processes which improve these pieces life span and mechanical properties are more valuable. Devices used in different methods mostly have problems such as high supply or utilization costs, accessibility limitations, or difficult usages. Accordingly, to fulfill these demands electrospark deposition is introduced as a suitable method. In this research, an electrospark deposition device was built by laboratory equipment under laboratory condition; therefore, to design this device Altium designer software and PCB print application, and current electronic pieces in electronic boards was used. To evaluate built electrospark device accuracy, and prepare testable samples, tools steel sheets used as a substrate and a cobalt base alloy electrode named stellite ۶, in a single splat and completely deposited conditions was prepared. Evaluated parameters in this study was voltage, condenser capacity, and shield gas which respectively were ۳۵ to ۷۰ volt, and ۳۵۶۰ to ۴۹۲۰ micro-farad with or without the presence of argon shield gas. Optical microscope (OM), scanning electron microscope (SEM) and (BSE) images were used to evaluate results, and to evaluate the coats final hardness of electrospark deposition, each sample was tested ۲۵ repetitions by Vickers-BUEHLER microhardness machines, and to quantitative survey, Image J and MIP software were used. In single splats, dimensions including diameter and volume of samples increased by rising voltage and condenser capacity and this increase was more notable in depositions in the presence of argon shield gas. When voltage and condenser capacity were in their maximum amounts with ۷۰ volt and ۴۹۲۰ micro-farad, coats thickness were ۴ times more, and when these parameters were in their minimum with ۳۵ volt and ۳۵۶۰ micro-farad, coats thickness were thinner and the coats thickness stayed stable after a while and increasing depositing time had no effect on the best thickness dimension which is due to the electrode material dispersal to other coat spots after reaching to the best coating condition. Coating monotonousness in a deposition with the presence of argon shield gas is more than the deposition without it. There were no cavity or crack in samples surfaces with low voltage and condenser capacity and their structure were completely dense. While in samples with more spark energies (higher voltage and current) cracks and cavities were visible based on the images from inner crack crust due to the non-formation of freezing phases, cracks were residual stresses kinds, also in more condenser capacity, average crack lengths were higher as well which these defects decrease samples corrosion and wear resistance. Compared to the stellite ۶ hardness which it is ۳۵۰ vickers, electrospark deposition increased hardness of stellite coats nearly five times and examinations revealed the highest hardness rate of the coat located in the core of the coat and was ۱۸۵۴ Vickers and the lowest hardness rate located in the coat surface and the boundary between the coat and the substrate which was ۹۲۰ Vickers. With due attention to the parameters effects and considering desirable result of samples fixing or coating, the best parameter is chosen as depositing coating by electrospark.

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