ZnAlMg Hot-Dip Galvanised Steel Sheets – Tribology and Tool Wear

Abstract

For the last few years zinc magnesium alloys on cold rolled steel have been investigated in detail because of their potential to provide better corrosion protection than pure zinc coatings. However, for the introduction into the automotive industry it is also necessary to learn more about their tribological behavior. In this paper the tribological potential of ZnAlMg hot dip galvanized steel sheets (HDG/ZM) was studied in terms of sliding properties, adhesive and abrasive tool wear and compared to hot dip galvanized reference material (HDG/Z). Different tribological tests were performed. The friction coefficient was determined directly by strip draw tests at constant contact pressure. The deep drawing property was tested by forming model cups. Two different oils, a pure corrosion protection oil and a prelube were tested in each of the tribological tests. Abrasive tool wear was studied according to the SEP1160 standard. Adhesive tool wear (galling) was characterized on different tool material and compared to the results for hot dip galvanized reference material. HDG/ZM strips showed improved friction behavior in the strip draw test when compared to classical hot dip galvanized reference material. The abrasive tool wear is comparable to HDG/Z material, however, the galling was found to be less than for pure zinc, and the morphology of the coating material transferred to the tool during deep drawing is also different. This makes HDG//ZM an interesting system not only with respect to corrosion but also in terms of tribology, thus providing clear advantages in formability.