1. Introduction

Brass alloys and H13 hot work tool steel are conventionally used in hot forging materials for workpiece and for tool material, respectively. They are also employed for the produc tion of such parts as gas valves (Ref 1, 2). The tribological properties of H13 steel and CuZn39Pb3 brass alloy at room temperature after oxidation at 600 C indicated that a loose oxide film wholly covered the surface of the steel (Ref 3). In the last two decades, much research has been done to improve the die life in the field of hot forging steel alloys by surface engineering methods (Ref 4). However, in the case of hot forging copper-based alloys, there are few studies regarding the die life improvement. In 1998, in the area of forging copper alloys, Sato et al. (Ref 5) studied wear and tribological properties of PVD coatings rubbed against copper at ambient temperature. The wear rate of CrN rubbed against copper was at a very low level, but the wear rate of TiCN, TiN, and TiC, as tested under the same conditions, and was higher than that rubbed against hardened high speed tool steel substrate at room temperature. In the case of forging steel alloys, the best die life was observed when duplex coating and ternery thin layers (TiAlN or CrAlN) were used (Ref 6-12). There has been no research in the field of duplex coating and ternery thin layers dies for forging of brass alloys, but a recent study