Erosion process analysis of die-casting inserts for magnesium alloy components

Erosion of die materials during die filling has long been regarded as possible damage mechanism of dies in high-pressure die casting (HPDC) of magnesium alloys. Melt impingement and erosion have also been proposed as important steps leading to die washout. However, little information on direct measurements of any type of die insert erosion in HPDC is available. The present analysis shows the insert surface states and chemical compositions of a failed die obtained from a die casting plant. Results show the presence of numerous microholes, microcavities and cracks on die surface. The diameter of the smaller microholes is about 9 μm, whilst that of the larger microholes is over 100 μm. Mechanisms causing insert erosion are discussed. Erosion takes place through depression, plastic deformation and tearing actions resulting from both impact pressure and high-velocity lateral jets. These damage mechanisms create pits on the surface of eroded samples.