Study Of Mechanism And Application Of Active Screen Plasma Nitriding

Active screen plasma nitriding (ASPN) is a novel nitriding technology, which overcomes many inherent problems associated the conventional DC plasma nitriding (DCPN), such as difficulties in maintaining a uniform chamber temperature, arcing surface damage, the edging effects, hollow-cathode effects and so on. Active screen plasma nitriding can achieve similar nitriding effect as DC plasma nitriding for both low alloy steel and stainless steel. Active screen plasma nitriding will be a strong rival to the conventional DC plasma nitriding in the future.In this dissertation, the mechanism of active screen plasma nitriding, nitriding in pure nitrogen atmosphere were studied by means of collecting particles sputtered from the active screen. The high speed steel nitrided by active screen plasma nitriding was also studied. Surface Morphologies, composition and microstructure of the particles were observed and analyzed by means of field emission scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD). The microstructure and cross section microhardness of nitrided layers were observed and analyzed by optical microscope (OM) and microhardness tester. The main experimental results are as follows:The process of active screen plasma nitriding should be a process of physical adsorption and desorption. The paticles sputtered from the active screen are Fe_xN(x>2), which are in nanometer scale. The particles adsorb physically some nitrogen atoms during transferring from the active screen to substrate surface. The...