Characterization of Formed TRIP1180 Steel Sheet Surface After Stamping with PVD-Coated Tools

Abstract

The wear tests are conducted on bending punches deposited with PVD CrN and AlTiCrN coatings using the newly proposed progressive die. Then, the surface quality of the formed product is characterized through the surface roughness measurement after forming of TRIP1180 steel sheets. The correlation between the tool wear, in terms of wear depth and roughness and the product surface roughness can be quantitatively analyzed. The results show that the roughness remains comparable to that of the as-received surface before failure occurs, which represents smooth product surface without severe scratches and defects. While micro scratches on the punch surface have no effect on the quality of the product surface, severe fretting wear on the punch surface leads to a deterioration in the surface quality. Once initiated in the stamping process, the wear progresses exponentially within short time. The wear is also characterized as less than the coating thickness, but it results in complete removal of the coating layer. The partially worn punch plows the product surface, causing surface scratches with grooves and ridges, resulting in the roughness of 1.0 μm. In contrast, the surface with completely damaged coatings is extremely rough, with the roughness of 2.0 μm. This study presents the efficient method to evaluate the tool wear progression by indirectly measuring the product surface quality with reliably high precision.Graphical abstract