Abstract
This study reported the effect of thermal wear on cylindrical tool steel (AISI H13) under aluminum die-casting conditions. The AISIH13 steels were immersed in the molten aluminum alloy at 700 °C before water-quenching at room temperature. The process involved an alternating heating and cooling of each sample for a period of 24 s. The design of the immersion test apparatus stylistically simulated aluminum alloy dies casting conditions. The testing phase was performed at 1850, 3000, and 5000 cycles. The samples were subjected to visual inspection after each phase of testing, before being examined for metallographic studies, surface crack measurement, and hardness characteristics. Furthermore, the samples were segmented and examined under optical and Scanning Electron Microscopy (SEM). The areas around the crack zones were additionally examined under Energy Dispersive X-ray Spectroscopy (EDXS). The crack’s maximum length and Vickers hardness profiles were obtained; and from the metallographic study, an increase in the number of cycles during the testing phase resulted in an increase in the surface crack formation; suggesting an increase in the thermal stress at higher cycle numbers. The crack length of Region I (spherically shaped) was about 47 to 127 µm, with a high oxygen content that was analyzed within 140 µm from the surface of the sample. At 700 °C, there is a formation of aluminum oxides, which was in contact with the surface of the H13 sample. These stresses propagate the thermal wear crack length into the tool material of spherically shaped Region I and cylindrically shape Region II, while hardness parameters presented a different observation. The crack length of Region I was about 32% higher than the crack length of Region II.
Highlights
It is crucial in aluminium die casting to manufacture more than 100,000 castings per die application, but this often results in die failures
AISI H13 tool steel and aluminium 356 alloys were employed in this study
The effect of silicon and aluminium can be caused by the short crack within the surface, negative effect of the oxide layer, it was at is its lowest thermal expansion and higher volume and meaning that they were in contact with the molten aluminium alloy
Summary
It is crucial in aluminium die casting to manufacture more than 100,000 castings per die application, but this often results in die failures. In the presence of defects due to erosion within the die, there is always a contact between the die surface and the molten material, which will subsequently lead to intense erosive reaction after many cycles [3]. Some of the prominent die failures noted includes washouts, soldering defects due to die-molten metal contact, and thermal cracks [4,5,6,7,8]. Maiya and Burke [9] have demonstrated an increase in life when sheet-metals are exposed to tests for thermal fatigue, with a decrease in the thickness. At the end of each testing cycle, the processed samples were examined for the development of metallurgical and mechanical behaviors, as well as checking for the initiation of thermal cracks [22,23,24]. The micro-hardness profiles of the cycled specimens were assessed for behavioral changes after cyclic immersion tests
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