Failure of Physical Vapour Deposition Coating Zirconium Nitride on the Punch of Clinching Tool

A tool with a punch of ø5 mm and a die with a specially formed circular cavity and an annular gap was used for mechanical joining of thin hot-dip galvanized steel sheets. The active parts of punch and die were covered by PVD coating of ZrN type with LARC technology. The punches and the dies were tested in a complex tool by joining thin hot-dip galvanized steel sheets with the pressing force of 7,000 N. Decohesion of coating with width of 100 – 200 μm was observed in the perimeter of cylindrical part of ø5×4 mm in the in edge of punch radius R = 0.5 mm with deposited ZrN coating after the creation of 150 mechanical joints. The decohesion of PVD coating occurred mainly in the surroundings of the radius R = 0.5 mm on the front plane of ø15 mm part.