Laser Treatment of PVD Coated Carbon Steels and Powder Steels

Abstract

In the present study, the opportunities of laser beam treatment by the means of the 4 kW Nd:YAG laser are investigated. The studied materials are carbon steels C 45 and C22E (carburized), coated with the PVD coatings Ti(C,N), TiN and (Al,Ti)N, and powder steel Vanadis 6. The macrophotos of the laser beam treated surfaces were taken, the microstruc-tures of the cross-sections of laser beam treated specimens were studied, and the microhardness profiles of the cross-sections of laser beam treated specimens were made. As these studies have shown, no signs of the influence of laser beam appear at the surface of the PVD coatings, until an energy input threshold is reached, after that the coating oxidizes and degrades. No hardened zones were found under the PVD coatings, except for (Al,Ti)N coating. In the case of steel Vanadis 6, three distinct zones can be seen. In the first zone, the carbide particles have dissolved, and a dendritic struc-ture has appeared. In the second zone, the carbide particles remained, however, they were of smaller size in comparison with the initial structure. In the third zone, the initial structure remained. The growth of microhardness values was observed in the first and in the second zone, whereas bigger values were obtained in the second zone.