Mechanism of Galling Generation Using TiCN Coating in Finish Blanking - Thermochemical Simulation and Elemental Analysis -

The mechanism of galling generation is studied with finish blanking using TiCN coated punch. A high-tensile-strength-steel plate with a thickness of 6mm is used in the present paper. The edge shapes of punch are two types, a punch with 1.0 mm chamfered edge (C1.0 punch) and a punch with right angle edge (RA punch). The clearance is kept to 0.5%t, and lubrication is not used in this experiment. Galling is observed at the first shearing operation except for RA punch, and galling can’t be found clearly even when the shearing number reaches 20 in the case of the RA punch. In order to clarify these differences of RA punch and C1.0 punch, the oxygen on burnished depth is observed by electron probe micro analyzer (EPMA). The oxygen is not detected on the burnished depth sheared by RA punch. On the other hand, the oxygen is detected on the burnished depth sheared by C1.0 punch. In the case of C1.0 punch, the oxide scale on the plate surface flow into the burnished depth because of the low surface expansion ratio of the burnish depth. Thermochemical simulation is carried out using a commercial code MALT and gem which solves chemical equilibrium problems by minimizing the gibbs energy of the system. TiCN reacts with oxide scale to form Fe and Fe4N. As result of analyzing galling part of C1.0 punch from the cross section direction, Fe, Fe4N, FeTiO3 and Fe2TiO4 are detected and those detected elements coincides well with the Thermochemical simulation.