Tool Material Performance During Draw Bead Deformation of Aluminum Sheet

Draw bead simulator tests were performed on various tool materials using aluminum alloys 2008-T4 and 6111-T4. The tool materials included hardened cast steel J435/0050A, D2 alloy, cast steel with ion nitride and PVD chromium nitride surface treatments, and cast steel with standard chromium and Wearalloy™ chromium coatings. Friction and galling behavior were monitored over an extended period of testing which allowed differentiation of the tool materials and alloys. Wearalloy™ and CrN tool coatings consistently demonstrated improved ability to prevent material transfer for both aluminum alloys, in spite of friction coefficients which were higher than the uncoated and ion nitrided tools. The ion nitrided surface exhibited the lowest friction coefficients of the surface treatments tested, but showed appreciably more wear. For a given lubricant and dilution ratio, alloy 2008-T4 exhibited an increased tendency for material transfer compared to alloy 6111-T4 for all tool materials tested.