Investigation of the Effects of Temperature and Contact Pressure on the Friction Coefficient in Uncoated PHS2000 Steel Plates

Manganese-boron steels are widely used in hot stamping, resulting in 1500 MPa (PHS 1500) or even 2000 MPa (PHS 2000) tensile strength after the hot stamping process. These steels are most commonly used in industry in the form of AlSi-coated sheets. However, recent developments are being made to enable the application of uncoated steels, resulting in cost reduction, but bringing technological challenges to be overcome. The coefficient of friction (µ) is a fundamental parameter in sheet metal forming and is influenced by several factors, such as: surface roughness, working temperature, lubrication, contact pressure and sliding speed. In hot stamping, it is known that the temperature can have a great influence on µ values for coated plates, but there is little information about uncoated steels. This work aims to investigate the tribological behavior of uncoated PHS 2000 steel plates using the pin-on-disk test. Tests were carried out under three temperatures (800 °C, 600 °C and 400 °C) and contact pressures of 5 and 10 MPa. Results showed that the friction coefficient tends to reduce with increasing temperature at a pressure of 5 MPa, as result of oxide formation on the steel’s surface. However, at a pressure of 10 MPa, this reduction was not observed.