The Effects of Heat Treatment on Microstructure and Mechanical Properties of AISI 4140 for Base Cutter Cane Harvester

Abstract

The effects of heat treatment on microstructure and mechanical properties of AISI 4140 for base cutter cane harvester were studied. The effect of heat treatment - i.e. the different quenching medium (water, oil and air mediums) and the different heat treatment condition (quenching, quenching+tempering, cover scrap cast iron+ quenching and cover scrap cast iron+ quenching+tempering) on the on microstructure and mechanical properties (hardness, impact toughness and bend test). The material AISI 4140 was purchased from local market in Thailand and an emission spectroscopy was applied to quantify the amount of elements in steel. The specimens were heat treated in an induction furnace. The resultant microstructure of materials AISI 4140 consists of martensite and retained austenite after quenching all mediums, which quenching in water it have more than in oil and air medium respectively. The microstructure of materials AISI 4140 after tempering process consists of bainitic structure (ferrite and epsilon carbide) and retained austenite, which tempering in water quenching condition it have more than in oil and air quenching condition respectively. The hardness, impact toughness and bended test are according to behavior heat transfer of quenching mediums. The material alloy steel grade AISI 4140 is the good candidates to promote the quenching in water ,oil and air medium and must be continuous to tempering process. The technique heating by cover scrape cast iron it was good for protected surface and decreased decarburization on surface of steels. But it is not necessary for control microstructure and mechanical properties.