Evolution of the tribological characteristics of several forming die materials

The purpose of the present study is to investigate the friction and wear characteristics of forming die materials. Three automotive sheet steels and five die materials were tested. The steels were aluminum-killed drawing quality (AKDQ) uncoated sheet, galvannealed sheet and hot-dipped galvanized sheet. The die materials were A2 tool steel, weld overlay, tungsten carbide, titanium nitride coated and zirconia. Bending-under-tension friction tests were performed to evaluate frictional characteristics and to examine the initial stages of wear. The sheet materials exhibited frictional characteristics that are relatively independent of the die surface. The galvannealed sheet had the greatest overall coefficient of friction, the hot-dipped galvanized coated sheet had the lowest and the AKDQ sheet had a value between that of the two coated sheets. Of the die materials tested, the tungsten carbide and the zirconia die materials exhibited the lowest coefficients of friction. The A2 tool steel and the tungsten carbide die materials maintained a relatively constant coefficient of friction throughout testing. Overall, the tungsten carbide die material had the best performance with respect to the lowest coefficient of friction and highest resistance to wear.