Abstract
The presented work is focused on the fatigue endurance improvement by using plasma nitriding. In this research the microstructure and fatigue properties of low-alloyed steel 50CrV4+QT were evaluated. The low-alloyed (manganese-chromium-vanadium) steel is commonly used after heat treatment – quenching and tempering – QT(.7). This steel is widely used for highly loaded machines and parts of road vehicles: crankshafts of diesel engines, shafts of driving gears, connecting shafts, pins, springs, axle shafts and piston rods. Steel is suitable for quenching and tempering and contains chemical elements which predetermine it to the chemical-thermal treatment: plasma nitriding. The fatigue limit was determined at the rotating beam fatigue. The fatigue limit improvement at 1 × 10⁷ cycles was 44 %. Explanation of the improvement is based on stabilized gradient of properties in treated layer.

Key words
plasma nitriding, low-alloy steel 50CrV4, rotating beam fatigue tests, fatigue endurance

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