Abstract
M-42 is Molybdenum-series high speed steel used as a cutting tool material because of its hot hardness and toughness properties. With the better hot hardness and wear resistance, M-42 is one of the most widely used tool materials for cutting tools. These Molybdenum steels are heat treated conventionally in four steps viz., preheating, austenitizing, quenching along with two stages of tempering. The main step in heat treatment, austenitizing is done with the aid of salt bath furnace by heating the tool steel to the austenitizing temperature (1260°C) with three stages of preheating. This method is often a time consuming process with most of the time and energy utilized for the achievement of the required temperature. This study deals with the rapid heat treatment of the aforementioned M-42 steel samples by the action of microwaves from a hybrid microwave furnace. The quenching is done as of in a conventional method using a neutral salt bath maintained at a temperature of 550 °C. Comparison between the rapidly heat treated specimen and the conventionally heat treated specimen With similar dimensions is carried out. The tempering processes for both the specimens were carried out conventionally. Mechanical properties such as hardness, microstructure, etc., are compared between the conventional and the rapid heat treated specimens. Scanning electron microscopy was also taken to study the grain refinement of the microwave heat treated steel specimen at a higher magnification. The comparison between the properties and the microstructure revealed minute changes in mechanical properties of the rapid heat treated specimen and also resulted in the marked drop of the heating time and the energy saving thereby reducing the costs incurred for the heat treatment process.
