Heat treatment is referred to as a process or set of processes which involves heating the material to the desired temperature, changing its microstructures, keeping it at these temperatures for a certain time and cooling. The aim of heat treatment is to subdual the material to the changes in temperature to change certain properties. Some of the heat treatment processes are hardening, annealing, relaxation, improving and thermal chemical treatment. The most common reasons for the heat treatment of steel are increased tensile strength, improved mechanical properties and the ductility and reduction of internal stresses. This paper discusses, in more details, steel hardening process that involves heating up to austenitization temperature, then cooling at a high speed to achieve greater hardness and a process of relaxtion to increase the toughness of the material. The practical part of this final paper was consisted of the heat treatment of the machine component AM.17-PT.87. The machine component AM.17-PT.87 was subdued to the process of the hardening to increase its initial hardness to the hardness of 63 HRC. After increasing the hardness, the workpiece was subjected to a process of relaxation, which reduces tensions left behind after the hardening.