Faculty Advisor

Sisson, Richard D.


Tempering is a metallurgical process by which low alloy steel’s toughness & ductility are improved. Tempering is conducted in a single or multi cycle temper. The goal of this project is to investigate the effects of single vs double tempering on the properties 4140 steel. Samples of 4140 steel were tempered at 300, 400, 500, and 600 ºC for a total of 4 hours in single & double tempers. The samples were Rockwell C hardness & Charpy V-notch impact tested. The microstructure was characterized with SEM; carbides were extracted from samples & measured using XRD. The results are analyzed using the Holloman–Jaffe parameter. It was found that a 4-hour double temper does not significantly alter the microstructure, hardness, or impact toughness of 4140 steel when compared to a 4 hour single temper.


Worcester Polytechnic Institute

Date Accepted

April 2018


Mechanical Engineering

Project Type

Major Qualifying Project



Advisor Department

Mechanical Engineering