Contact Fatigue Resistance of Gun Barrel Steels

Abstract

Structural steels can be used to produce barrels, due to their good properties. During the working cycle, steels are exposed to aggressive conditions such as thermal stress, fatigue, and wear. In this paper, two steels were selected, namely 30CrNiMo8 and 42CrMo4, which were abraded with a G40 ball bearing. All measurements were performed on a UMT TriboLab universal tribometer. The main goal of the experiment was to analyze and compare the wear of tool steels in contact with a bearing ball with a diameter of 4.76 mm. Experimental materials will be processed for three types of roughness. Both types of experimental steels were measured after the final heat treatment (hardening + tempering). The main goal of the paper was to determine how different technological surface treatment of the material will affect the abrasion resistance, and thus the life of these main materials at the point of contact with the projectile. The experiment shows that 30CrNiMo8 steel has at least the same coefficient of friction (COF) with respect to all measurement parameters. In contrast, the second investigated steel, 42CrMo4, showed a decreasing COF due to the increasing roughness of the measurement. The friction mechanism was subjected to adhesive wear on both steels. The wear of both steels at roughnesses Sa12.5 and Sa 6.3 showed the same values. With a finer roughness of Sa 3.6, 42CrMo4 steel showed 50% lower wear values.