Selective laser melting of alumina: A single track study

Abstract

Ceramics-based additive manufacturing is a complex process and the solidification mechanism and microstructural evolution are currently not fully understood. In this work, Al 2 O 3 single tracks were formed using a customised selective laser melting (SLM) system equipped with a high power diode laser. The effects of laser energy density (LED) on geometry, microstructure and micro-mechanical properties of Al 2 O 3 tracks were investigated. To better understand the solidification mechanism, a transient threedimensional thermal model was developed for predicting the thermal behaviour of the melt pool. The results indicated the use of high LED gave rise to decreased viscosity and surface tension of the molten alumina and led to localised melting of the substrate. Both, in turn, enabled the formation of a continuous solidified track. The solidified tracks were primarily composed of columnar dendrite. When relatively high LED (≥25.7 kJ/m) was applied, equiaxed dendrite appeared along the central line near the 2 track surface. The size of dendritic grains decreased with the decreased LED, attributed to the increased cooling rate at solidification interface. The micro-hardness of the solidified track was found to be inversely proportional to the grain size owning to grain boundary strengthening effect.

Single Tracks as a Key Factor in Additive Manufacturing Technology—Analysis of Research Trends and Metal Deposition Behavior

“…Using high-power diode lasers, Fan et al [18] studied the ceramics-based AM process, in particular, the effects of the energy density on the geometry, microstructure, and micromechanical properties of Al 2 O 3 single tracks. Barroi et al [19] evaluated the effects of the laser power on the shapes of single tracks based on LPBF single-scan tracks, and Riquelme et al [20] researched the effects of the laser-cladding process parameters on the geometry and dilution of a ZE41 magnesium alloy.…”

UQ eSpace

“…As many of these components are used in harsh operating conditions, a thermal barrier coating (TBC) is often necessary. With the current lack of effective surface modification techniques that can deposit such a coating, laser cladding is a promising process for forming ceramics into the desired layer (Fan, Z. 2018).…”

“…Alumina based ceramics are commonly used in the automotive and aerospace industries as they are one of the most versatile engineering ceramics currently available. The high hardness, wear resistance and high-temperature strength associated with alumina is significant for surface modifications in abrasive applications as they ensure the protection of the titanium part (Fan, Z. 2018).…”

UQ eSpace

“…Alumina ceramics find many applications in industry, including electronic devices, optics, biomedical devices and protective coatings [7,8]. Currently, ceramics are manufactured through techniques such as slip casting, injection moulding and extrusion [7]. These techniques are widely used in industry however; they involve inefficiencies that cannot be overlooked.…”

“…These techniques are widely used in industry however; they involve inefficiencies that cannot be overlooked. The most immediate of these, in terms of time costs and process complexity, is the need for extensive tooling and post processing such as sintering to form high quality parts with adequate densification, which involves a considerable risk of part distortion and crack formation due to shrinkage [7]. These factors place a demand on the manufacturing industry to innovate a more efficient means of ceramic part production.…”