Experiments of plasma nitriding on steel bar

Summary form only given. Surface modification of deformed steel bar was done with plasma nitriding technology to improve the corrosion resistance. In this experiment, pulsed DC plasmas were used with various processing parameters such as pressure, nitriding time, temperature, gas compositions, etc. It was found that various compound layers can be obtained depending on carefully selected plasma parameters. The depth of diffusion layers were measured up to several hundred micrometers. The corrosion resistance of the nitrided steels was evaluated with a corrosion tester which measures the corrosion current between a test sample and a reference electrode submerged in 3% NaCl solution. Hardness of the nitrided layers was measured with a Vickers hardness tester. The XRD results of the compound layers were also shown. To understand better the properties of pulsed DC plasmas, electrical and optical methods were applied during the processes. Comparison of several nitriding models with experimental results and the corrosion characteristics will be discussed.