1. Plasma hardening of steels provides hardened layers which in hardness, thickness, and wear resistance meet the requirements for hardened surfaces of many parts of various types of machines. 2. From the results of production and testing under service conditions of lots of hydraulic motor stators and troughs of conveyers it was established that plasma hardening provides high part life and a decrease in the labor requirement for their production. 3. According to preliminary determinations, plasma hardening is promising primarily for local surface hardening of parts. However, the area of use of this method may be quite broad, which requires further study.