Effect of duty cycle on surface properties of AISI 4340 using a pulsed plasma nitriding process

Abstract

"Plasma nitriding is a glow discharge technique, which is widely used to improve the surface properties of steel and its alloys, such as wear, corrosion resistance and hardness; additionally, it can increase fatigue strength. The aim of this work is to evaluate the effect of duty cycle on the surface properties of AISI 4340 low alloy steel, in a pulsed plasma nitriding process. The effect of duty cycle (applying a 10 - 80 % tON interval) on the surface hardness, treatment depth, compounds zone width and crystalline phase composition will be discussed. It has been found that for nitriding process at 540 °C in a gas mixture 50 % N2 - 50 % H2 at a constant pressure, using a discharge voltage of -800 V, duty cycle has a negligible effect on crystalline phase composition, even though the influence on surface hardness, treatment depth and compounds zone width is evident."