www.tjprc.org SCOPUS Indexed Journal editor@tjprc.org EFFECT OF HEAT TREATMENT AND MECHANICAL CHARACTERIZATION OF AISI 4140 STEEL BHAGYALAXMI, SATHYASHANKARA SHARMA & VIJAYA KINI Department of Mechanical and Manufacturing Engineering,Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, India ABSTRACT This work studies the outcome of heat treatment of AISI 4140 on wear, hardness, and tensile strength. The properties were compared after subject the specimen to annealing, normalizing, hardening and tempering. Amongst the methods used hardened specimen showed a hardness of RC45 and wear rate of near zero. Annealed specimen showed a Percentage Elongation of 15.56 and the tempered specimen had a tensile strength of 1109.4 N/mm 2 . KEYWORDS: AISI4140 Steel, EN19 Steel, Heat Treatment, Tempering, Wear, Quenching & Tensile Properties Received: Oct 30, 2018; Accepted: Nov 10, 2018; Published: Nov 29, 2018; Paper Id.: IJMPERDDEC201863 INTRODUCTION Heat treatment is one of the methods to change the structure of the material thereby to get the desired properties. Annealing, normalizing, hardening and tempering are commonly used heat treatments to alter the microstructure and mechanical properties of materials particularly steels. Annealing is a kind of heat treatment used in order to soften iron or steel materials and refines its grains due to ferrite-pearlite microstructure; it is used where elongations and an appreciable level of tensile strength are required in materials. In normalizing, the material is heated to the austenitic temperature range and this is followed by air cooling. This is done to get pearlite structure which results into strength and hardness greater than as bought specimen. In hardening, the steel or its alloy is heated to a temperature high enough to promote the formation of austenite, held at that temperature for certain duration and then quenched in oil or water at a suitable rate. Tempering is done to impart ductility and toughness to the hardened specimen [1-3]. Heat treated AISI 4140 steel is used as the material for bolts, gears, spindles, couplings, sprockets, tool holders etc. [4-6]. As annealing temperature increases, strength properties of steelmaterial decrease whereas plastic properties rise. A substantial lowering of strength or hardness values occurs at temperatures which are close to 600 °C. [7] Hardness must be high to avoid plastic deformation. If tempering is done at 550 0 C, higher hardness, tensile strength, yield strength, and ductility can be achieved for AISI H11 tool steel [8]. Hardened specimens shown greater tensile strength and hardness values with lesser ductility and impact strength when compared to other heat treated specimens. Hardening is recommended when the strength and hardness are the prime desired properties in the material. Water quenching resulted in higher tensile strength and hardness possibly due to the formation of martensite structure after quenching [9]. Medium carbon steel specimens quenched in palm oil during hardening Original Article International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) ISSN (P): 2249-6890; ISSN (E): 2249-8001 Vol. 8, Issue 6, Dec 2018, 603-610 © TJPRC Pvt. Ltd.