Development of a method for assessing erosive wear damage on dies used in aluminium casting

• A new method has been developed for assessing aluminium erosion of casting dies.
• New understanding has been gained of aluminium erosion of steel.
• Use of cylindrical specimens allowed a range of contact geometries to be achieve.

During pressure die casting of aluminium, molten/semi-solid droplets of aluminium come into contact with the die surface. A number of damage mechanisms can occur as a result of this event, some related to thermal effects and some mechanical effects such as erosion. Dies are very expensive to manufacture and options for improving die life would be beneficial.Very few test methods exist to study the damage mechanisms and for trialling new materials/coatings. Most studies have involved either casting actual components or placing material specimens in a die casting machine so that they are impacted by the aluminium. This is very time consuming and expensive.In this work a laboratory test was developed specifically to study the erosion effects of the aluminium particles. A mounting frame was utilised to hold both flat and cylindrical specimens made from H13 steel (typically used for die manufacture). The frame was placed in a shot blaster which was used to fire aluminium balls (3 mm diameter—based on aluminium droplet size calculations) at the specimens. Different velocities were used and the flow was pulsed to mimic successive castings being made.Flat specimens were tested at different angles and cylindrical specimens were tested central to the flow of aluminium and in an eccentric position to cover a range of possible aluminium/die impact scenarios. Optical microscopy and roughness measurements were used to characterise the wear on the specimens. Wear rates were also determined. Behaviour was compared with data from the literature where available. Wear damage was also compared with worn dies. High speed videoing was also used to study the impact behaviour of the aluminium balls.It was concluded that the test method was a suitable approach to use in identifying potential solutions that could extend die life. In future work the effects of temperature and application of coatings will be explored.