Hardness Analysis for Low-Temperature Plasma Nitriding RF-DC of TIG Welding Joint Al 6061 Sheets

摘要

Automotive part such a block machine, piston crowns, piston rings, and piston-cylinder are made by Aluminum Alloy 6061 that has a standard of hardness. Several parts of the piston require a joint under a welding process which unfortunately decreases mechanical properties of the joint welding area, especially the hardness. The high temperature causes the reduction of hardness during TIG Welding process. RF-DC plasma nitriding with a gas ratio of 70% Nitrogen and 30 % Argon at low temperatures below 200°C can elevate the hardness of the welding joint. The highest increase of the hardness was achieved by 4 hours nitriding. EDS result showed an increase of nitrogen in their lattice. Solid solution hardening mechanism in this plasma nitriding process was occurred because of the strained lattice of aluminum.