Abstract
The coefficients of friction of uncoated high-strength steel sheets and galvannealed high-strength steel sheets were investigated by sliding tests at elevated temperatures using uncoated tools and TD-coated tools with a VC layer on their surface. The temperatures in the tests ranged from room temperature to 700°C. The coefficients of friction of the tested steel sheets at elevated temperatures are higher than those at room temperature. The coefficients of friction of the uncoated steel sheets are much higher than those of galvannealed steel sheets. The phenomena during the sliding tests were clarified by observing the surfaces and cross sections of the tested steel sheets. The sliding behavior of the uncoated high-strength steel sheets at high temperatures depends on adhesion to the tools and the scale on the steel sheets. For the galvannealed high-strength steel sheets, the sliding behavior at high temperatures depends on the strength of the coating layer. The effects of different factors such as lubricant, surface conditions, adhesion to the tools, and material strength on the coefficient of friction were also examined in this study and presented in this paper.
