Abstract
Depositions of surface coating materials is one of the important approaches in improving friction and wear properties of the surface, there is a growing demand for low friction coatings like TiN, TiAlN & WCC that allow contacting surfaces to rub against with reduced friction and wear. Selection of different types of Nitriding process and coatings used on AISI 4140 steel to improve tribological properties by Multi Criteria Decision Making methods (MCDM) .The MCDM method used for selection namely TOPSIS (technique for order performance by similarity to ideal solution). Analytical hierarchy process (AHP) is used to find out weightage for the material criteria’s like young’s modulus(E), Hardness (H),H/E ,H 3 /E 2 and critical load for adhesion of coating for AISI 4140 steel. Each property is measured according appropriate standard. Selected AISI 4140 steel is optimized for tribological test settings using the grey relational analysis method. Taguchi method is implemented for experimental design which gives nine experimental runs based on orthogonal array. Coefficient of friction (COF) and wear is measured for nine different test on Pin on disc Tribometer. The optimal setting is selected and confirmation test is performed which gives clear indication of best material as well as optimum operating condition for AISI 4140 steel. Keywords— COF, Pin on Disc, Taguchi, TOPSIS, Wear. INTRODUCTION The machining industry is constantly seeking ways to enhance performance (metal removal rate) and reduce cost of the manufactured parts. One way to enhance the machining performance is to utilize high speed machining. One of the problems associated with high speed machining is the high tool wear, leading to reduction in tool life. When the normal load and the sliding speed increased, the friction coefficient in air increased from 0.65 to 0.72, whereas decreased from 0.58 to 0.36 in water and 0.20 to 0.08 in oil [1] . The wear resistant and thermally stable oxides formed by the tribo-chemical reactions of chromium and aluminum protected the AlCrN coating against wear admirably [3] . The results showed that the AlCrN coating exhibited higher hardness, but lower wear resistance as compared to the CrN coating. The AlCrN coating formed by CrN alloying with aluminum would show significantly improvement in high temperature oxidation resistance but not necessarily in wear resistance under the condition of ambient temperature [4] . The superiority of the AlTiN coating is confirmed by wear rates estimations [5] . Plasma nitriding has been carried-out to enhance surface related properties of steel components. The hardened case in these components comprise of a compound (white) layer on top followed by a diffusion zone underneath it. The increase in hardness and strength at the surface, yield improvement in fatigue life. However, increase in thickness of the compound layer beyond a certain critical reduces the fatigue life of the base material [7]. CrN coating gives better result against wear under dry and lubricated condition. AlCrN coating showed
Published Version
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