Design of a test rig for the characterization of friction and wear in hot-metal gas-forming of AA 5083 aluminium sheets

Abstract

Advanced aluminium sheet-forming processes such as the hot-metal gas-forming represent a challenging solution for producing small lots in the high-end car bodies industry, and the adoption of single cavity moulds made from low-cost, easily machinable materials such as cast iron reduces the overall sheet-forming costs. The tribological properties of the mould-sheet tribopair are of great interest for optimizing the sheet forming obtaining an acceptable esthetic surface finishing. This study presents the design and construction of a lab-scale experimental test rig for the tribological characterization at high temperatures of the mould-sheet tribopair. The proposed test method reproduces the sliding at the mould-sheet interface with contemporary sheet straining up to ε = 0.8 at strain rates in the 1.2∗10⁻³ to 2∗10⁻² s⁻¹ range. A series of experiments were carried out in dry and lubricated conditions for a ductile iron EN-GJS grade sliding against a AA 5083 aluminium alloy while straining. After comparing the experimental results with the literature data from other test rigs, comparable results were obtained as COF regards, ranging between 1.2 and 2.5 in dry sliding and between 0.05 and 0.2 in lubricated sliding. The morphological characterization of the sliding surfaces and cross-sections highlights the strong tendency to galling in dry sliding conditions expecially for low strain rates.