description
Pulse-plasma nitrocarburizing is a thermochemical process, which is used to upgrade the surface properties of mechanical parts made from lowžallozed and heat-treated steel, through the formation of an nitrocarburized lazer, characterised by high hardness and superior wear and corrosion resistance. Because the process is carried out at relatively low temperatures, there is little or no distortion of the mechanical parts during the process. Gas shock absorbers' piston rods from heat-treated steel W.No. 1.1191 were pulse-plasma nitrocarburized at 580$^{\circ}$C in a gas mixture atmosphere containing 87% N$_{2}$, 11% H$_{2}$ with 2% CO$_{2}$ additions, at a voltage of 375 V and a current of 37 A. The pulse width was 0,480 ms and the pulse pause was 0,020 ms. Distortion of the gas shock absorbers' piston rods increased from 0,00 mm to 0,06 mm on average. The surface roughness Ra increased from 0,125 ?$\mu$?m, on average, to 0,207 ?$\mu$?m on average (cca. 60%). The surface hardness of the gas shock absorbers' piston rods with a core hardness of 195 HV1 is 587 HV1, on average. The total depth of the nitrocarburized case (Nht) is 0,52 mm, on average. With use of classic of metallographic techniques the presence of the compound layer, consisting ?$\epsilon$? - Fe$_{2,3}$(N,C) and ?$\gama$? - Fe$_{4}$(N,C) phases was observed on the surface. The average thickness of this layer was 23,9 ?$\um$?m.