Boriding of 2365 and 2344 steels by plasma electrolysis technique and investigation of surface properties

Industrial organizations tend to use long life, durable and economical materials according totheir policies and in order to reduce their manufacturing costs. Steel, whose surface is corruptedand which become impossible to process as a result of these effects, constitutes importantproblems in terms of manufacturing costs. Surface modifications are needed in order toincrease the life of these steel materials, which are operated in industrial systems. Nowadays,material surface modification and surface treatment are very attractive subjects. People budgetsurface modifications not only because of their economic advantage, but also due to potentialcontributions they will make to the quality of manufacture. Increase in the interest to surfacemodifications has brought along new surface treatment techniques. In recent years, usage ofplasma environment for surface treatment is a common area of study. In this study, differentnomenclature are used according to different conditions, where plasma environment areprovided, and in this very study, the main target is to obtain a material of high hardness and toincrease the abrasion and corrosion resistance of the material.In this thesis study, by using pulsed plasma electrolysis technique, boriding has been carriedout on 2365 and 2344 steel surfaces, which are widely used as hot tools and mold steel. In thisstudy, steel samples which are subjected to plasma electrolytic boriding (PEB) technique, areselected, and with the help of improved surface conditions after the PEB process, increasing thelife and productivity of the sample in industrial operations is targeted. Specially prepared for thetesting apparatus, 15 mm in diameter and 5 mm high steel roller samples, are sandpapered andpolished prior to the operation. In the testing apparatus, which has been specially designed inorder to provide a pulsed plasma environment, two different processing times and two differentelectrolyte concentrations have been used as working parameters. For researching thestructural characteristics of the boron layer, which has been formed on materials after the PEBprocess, scanning electron microscopy (SEM), x-ray diffraction (XRD) and energy dispersive xrayspectroscopy (EDAX) techniques have been employed. Microhardness measurements,abrasion test, surface friction coefficient detection and surface roughness values are reviewedin order to see the changes in tribological performance of the boron layer formed in steelsurface.As a result of the structural and tribological analyses after the testing process; this thesis studyhas been found to be in conformity with the studies which are stated in the literature. Whenaverage layer thicknesses from SEM images are reviewed, it has been seen that when theprocessing time is extended, layer thicknesses are also increased; moreover, increasing theelectrolyte concentration has also increased the layer thickness. Peaks, seen as a result of theXRD analyse in 44 and 65 degrees are thought to be belonged to the FeB structure, as statedbefore in the literature. When micro hardness values from the steel sample cross sections, ithas been seen that the layer thickness values are between 1200 and 1600 HV. Extension of theprocessing time using the same concentration resulted as an increasing effect on the layerthickness. In consequence of plasma electrolytic boriding technique applied to the 2365 and2344 steels, which are widely used as hot tool steels in the industry, a significant decrease inabrasion rates has been obtained. After the boriding process on 2365 steel, 5-6 times moretreatment rate has been obtained in abrasion resistance of the long processed sample in 10 %electrolyte concentration, in comparison to the main material. The effect of plasma electrolyticboriding technique on surface roughness rate is a very significant subject. In this study, in whichthe industrial usage possibilities have been considered, increase in the surface roughness ratesof the steel samples and the existence of the variable values are actually unwished for. When itis taken into account that the 2365 and 2344 steels, used in this thesis study, have beenrecycled after they are abraded, the importance of this study is very significant for economicalreasons.Keywords: Surface Coating, Plasma Electrolysis, Boriding, Surface Characterization,Tribological Characteristics