Fabrication of Al₂O₃‐SiO₂ ceramics through combined selective laser sintering and SiO₂‐sol infiltration

Abstract

Investment casting, which is almost independent of part size, shape, and quality, enables the production of castings that are lightweight, thin-walled, and complex in shape. 1 It is one of the main techniques for the production of high-temperature precision alloy castings such as aero-engine turbine blades, turbine disks, guide belts, and combustion chambers. During the investment casting process, the ceramic molds 2 (shell and core) are used, and molten metal may be gravity poured or forced by applying positive air pressure. The fabrication of ceramics molds with the current method usually involves the shaping of the wax pattern, impregnation of the wax pattern into the slurry, and sandblasting, dewax, and burnout. This process is faced with the problems of high-cost, time-consuming, and low yield rate, especially for ceramics mold with

A review on the ceramic additive manufacturing technologies and availability of equipment and materials

“…The process commonly uses coarse ceramic powders (10-100 μm [17]) to guarantee flowability and the formation of uniform powder layers [6,14]. The main process parameters to be considered are laser beam power, laser scan speed, scan spacing, and layer thickness [146][147][148] and an orthogonal method may be performed for optimization [151][152][153]. In recent work [151][152][153][154][155][156][157][158][159][160], the parameters have varied in the following range: laser power: 6-12 W; scanning speed: 1500-2500 mm/s; scan spacing: 50-150 μm; and layer thickness: 100-200 μm.…”

“…The main process parameters to be considered are laser beam power, laser scan speed, scan spacing, and layer thickness [146][147][148] and an orthogonal method may be performed for optimization [151][152][153]. In recent work [151][152][153][154][155][156][157][158][159][160], the parameters have varied in the following range: laser power: 6-12 W; scanning speed: 1500-2500 mm/s; scan spacing: 50-150 μm; and layer thickness: 100-200 μm. Also, a pre-heating of the powder bed can reduce thermal stresses and thus help prevent crack formation in sintered parts [147].…”

“…Most recent research on ceramic SLS has been done by the State Key Laboratory of Material Processing and Die & Mould Technology from Huazhong University of Science and Technology (Wuhan, China) [151][152][153][154][155][156][157][158][159][160]. Their research focuses on improving the ceramic parts produced by SLS by considering adding additives (CaSiO 3 [154], Al [157]), adjusting process parameters [151][152][153] (laser power, scanning speed, scanning space), sintering temperature [155,156], and particle size distribution of the raw materials [158,159], and by combining SLS with other processes such as vacuum infiltration [152]. Such works have shown the potential use of this technology to produce ceramic cores (to fabricate turbine engines and gas turbine hollow blades) and high porous ceramics (used for thermal insulators, filters, catalyst supports, separation membranes, etc.).…”

“…Such works have shown the potential use of this technology to produce ceramic cores (to fabricate turbine engines and gas turbine hollow blades) and high porous ceramics (used for thermal insulators, filters, catalyst supports, separation membranes, etc.). The SLS technology can be used to fabricate parts with low firing shrinkage (<5% [155,156,158]) due to the low content of binders (which typically ranges from 7.5 to 15 wt% [152][153][154][155][156][157][158]). The sintered bodies typically have low relative density, with porosity usually greater than 50% [151,[154][155][156][157]160], and may exceed 85% [155,156].…”