Tribological Investigations on Tool Surfaces for Temperature-Supported Forming of Magnesium AZ31 Sheets

Abstract

Aiming to decrease friction coefficient ( μ ) during the forming of magnesium alloy sheets, nine (9) tools with different hole geometries in their surface (flat, elliptical, and circular) were manufactured from steel Boehler W400 VMR (as known as DIN 1.2343). Tribological investigations were accomplished on a strip drawing machine at 288 °C without lubricants. When compared with a standard tool (surface flat), on average, tools with circular geometries in their surface showed the smallest friction coefficient, while tools with elliptical geometries shown higher. The friction coefficient also was confronted with the ratio between area occupied by holes in the surface of the tool and the total tool surface (i.e., factor f (%)), hole diameter (Ø), and the distance between circle centers (d(c,c)). Principal Component Analysis (PCA) complemented the experimental approach. In summary, both approaches (experimental and theoretical) indicated that the manufactured tool with circular geometries on its surface presented lower friction coefficient values on the forming processes of the magnesium AZ31 sheets.

Approaches for Preventing Tool Wear in Sheet Metal Forming Processes

“…PVD and CVD methods enable the formation of hard layers, primarily nitrides and carbides, as well as borides and some metal oxides on forming tools. Dos Santos et al [119] list the processes of deposition of thin multilayer coatings, of which the following are dominant: chemical deposition of nanometric surface layers by the CVD method, pulsed laser deposition and molecular beam epitaxy.…”

Evaluation of the Friction Coefficient for TRIP1000 Steel under Different Conditions of Lubrication, Contact Pressure, Sliding Speed and Working Temperature

“…The results reveal that friction varies substantially for each situation and better in-depth studies are necessary for each material and boundary conditions. Additionally, there are works are more focused on the analysis of the types of surface that generate less friction [6,7], where the best surface preparations for lubricated and dry-forming processes were found. There are also efforts to understand how the performance of lubricants will occur over the lifetime of the tools [1], where lubricants were tested for 1200 strokes of parts during punch cutting and those more suitable for mass production were selected.…”