Application of Appropriate Coatings on Extrusion Dies and Evaluation of Their Performance During Hot Extrusion of Aluminum

The aim of this paper is to study the effect of extrusion parameters (extrusion speed and temperature), die geometry, and the application of appropriate coating materials on the extrusion dies in order to extend their working life. To achieve the above goal FEM techniques and experimental tests adopted and simulating and experimental results evaluated. In this way, special FEM software was used to set up the finite element model of the aluminum extrusion. As a billet material the 6061 aluminum was used, with a specific diameter and length. The extrusion process was modeled as isothermal, which means that the billet material preheated at the specific temperature and then it was pressured into the two different dies, with a specific extrusion ratio. The extrusion speed was varied between 0.5 to 1 mm/sec and the extrusion temperature varied between 400 °C to 500 °C. The extrusion angle of the two different dies was 9° degrees. The fillet radius at the top surfaces was selected to be 1 mm. The friction between aluminum material (billet) and the extrusion equipment was i) aluminum material and die 0.3, ii) aluminum material and ram 0.9 and iii) aluminum material and container equal to 0.96. Optimized algorithms of extrusion parameters were proposed regarding to the concluded simulating results. The results obtain from the simulation procedure help to the better understanding of the specific extrusion process, leading to better modification of the experimental procedure. In this way, experimental tests were conducted on special laboratory extrusion press using the two different die geometries coated with three different PVD coatings. By means of these experimental tests the additional working life of the coated dies, during hot extrusion process, was able to be evaluated. In addition, the three different coatings where tested by established quality procedures in order to determine their behavior on the material of the extrusion die.