International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 08 Issue: 01 | Jan 2021 www.irjet.net p-ISSN: 2395-0072 © 2021, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 1695 SLIDING WEAR BEHAVIOUR OF HVOF SPRAYED WC-12CO BASED COATINGS ON AISI 4140 STEEL ALLOY Balakrishna A M 1 , D G PRADEEP 2 , Dr. H S Nithin 3 1 Student, Dept. of Mechanical Engineering, Malnad College of Engineering, Hassan, Karnataka, India 2,3 Assistant Professor, Dept. of Mechanical Engineering, Malnad College of Engineering, Hassan, Karnataka, India --------------------------------------------------------------------------***----------------------------------------------------------------------- ABSTRACT- AISI 4140 steel alloy is a very weak and low alloy steels which depend on substances or elements other than carbon and iron to increase their mechanical properties like hardness, toughness, tensile strength. WC-Co coatings made by Thermal spray process are well known for their corrosion, wear and oxidation resistance. The co efficient of friction significantly decreases when a tribolayer is formed by the coatings under high temperatures in dry sliding contacts. In our current study we used compositions like Al2O3 and CeO2 that are mixed with WC-12Co powders and this composition significantly increased the wear resistance, performance at elevated temperatures. Here we used HVOF technique to produce coatings. The study we made shows that low co efficient of friction is produced by these coatings when compared to base metal AISI 4140 steel alloy. The coatings formed made tribolayer which was smooth and oxide based on the wear surfaces and the debris of wear included micro and nano metric crystalline oxide particles. KEYWORDS: AISI 4140 steel alloy, thermal spraying, HVOF, WC-12Co, Al2O3, CeO2, hardness and wear test. 1. INTRODUCTION Material wear is a common problem in many industries which cause material loss, that can result in refurbishment or replacement of component. This wear problem can be controlled by proper material selection. But change of base material leads to increase in material cost and leads to new challenges. The performance of the component can be improved by altering the surface by surface engineering techniques. One of the process in surface engineering is the thermal spraying that is the coating process that is used to impose thick wear resistant coatings on large surfaces. Spraying process is done by spraying the powder or wire form feedstock material in heated form. These heated particles are projected with great velocity on the surface of component and solidify and interlock with underlying surface. These thermally sprayed materials have application in many fields. In thermal spraying, hard metal materials are manufactured by sintering and agglomeration process. The current technique to manufacture hard metal coatings is HVOF (high velocity oxy-fuel) flame spray process. In this process particles are accelerated with high velocities (500-800m/s) and dense coatings are produced. The fuels used in HVOF technique are propylene, kerosene and hydrogen. The service life of materials or machine parts are reduced due to many problems. This service life can be improved by thermally sprayed coatings. Thermal spray coating has many other applications like for coated shafts, ball valves, piston sleeves operating at high temperature. The base metal used AISI 4140 steel has wide range of applications in connecting rods, hollow shafts, axles on forming disc, crankshafts and many more. The property of AISI 4140 steel alloy is low sliding wear resistance and unstable friction characteristics. The present investigation has been done to study the wear behavior of AISI 4140 steel in two different conditions. 2. MATERIALS 2.1 AISI 4140 STEEL Fig 1 AISI 4140 STEEL Base Metal AISI 4140 is produced in an electric or oxygen furnace by placing carbon, iron and other alloying elements in it. The alloying elements included in AISI 4140 are manganese, chromium and molybdenum. The properties of AISI 4140 are good hardness penetration and high strength, superior toughness, good wear resistance and good ductility.