PERFORMANCE OF COATED DIES IN HOT EXTRUSION OF ALUMINUM

The aim of this paper is to study the effect of extrusion parameters (extrusion speed and temperature), die geometry and coating material on the operation life of extrusion dies. To achieve the above goal, FEM techniques and experimental devices have been developed. Aluminum 6061 was used as billet material. The extrusion process was modelled as isothermal. The billet was preheated at a specific temperature and then it was compressed into 2 different dies possessing different specific extrusion ratios. The extrusion speed was varied between 0.5 and 1 mm/s and the extrusion temperature was in the range from 400 to 500 degrees C. Taking into account the extrusion process simulation results, an optimisation of the extrusion parameters was rendered possible. The mechanical strength of the 3 coatings was tested by nanoindentations, indentation adhesion tests and fatigue impact tests. By means of the proposed methodology, the increase in operation life obtained by applying appropriate coatings on the dies for hot extrusion of aluminum could be documented.