Additive manufacturing of ceramic structures by laser engineered net shaping

Abstract

Ceramic is an important material with outstanding physical properties whereas impurities and porosities generated by traditional manufacturing methods limits its further industrial applications. In order to solve this problem, direct fabrication of Al 2 O 3 ceramic structures is conducted by laser engineered net shaping system and pure ceramic powders. Grain refinement strengthening method by doping ZrO 2 and dispersion strengthening method by doping SiC are proposed to suppress cracks in fabricating Al 2 O 3 structure. Phase compositions, microstructures as well as mechanical properties of fabricated specimens are then analyzed. The results show that the proposed two methods are effective in suppressing cracks and structures of single-bead wall, arc and cylinder ring are successfully deposited. Stable phase of α-Al 2 O 3 and t-ZrO 2 are obtained in the fabricated specimens. Micro-hardness higher than 1700 HV are also achieved for both Al 2 O 3 and Al 2 O 3 /ZrO 2 , which are resulted from fine directional crystals generated by the melting-solidification process. Results presented indicate that additive manufacturing is a very attractive technique for the production of high-performance ceramic structures in a single step.

An Overview of Laser Engineered Net Shaping of Ceramics

“…On one hand, Silicon Carbide (SiC) suppresses cracks by dispersion strengthening mechanism, since it has higher binding strength and melting point, and so its dispersion in the alumina matrix demands more propagation energy. On the other hand, yttria and zirconia suppress cracks by grain refinement strengthening [29,30]. Niu et al [38] produced Alumina/YAG eutectic ceramic with a relative density of 98.6% and microhardness and fracture similar to those achieved by traditional methods.…”

“…Alumina was used as the raw material in 15 of the 16 employed articles related to AM of ceramics. It was employed to deposit Al 2 O 3 [8][9][10][27][28][29][30], Al 2 O 3 /ZrO 2 [29][30][31][32][33][34][35][36][37], Al 2 O 3 /YAG (yttrium aluminum garnet) [30,38] and Al 2 O 3 /SiC [29]. These manuscripts utilized powders with a particle size of about 40-90 μm.…”

“…It was shown by Durejko et al [39] that spherical powders have a smooth and problem-free feeding process during LENS fabrication. Moreover, some studies [8,[27][28][29][30]37,38] indicate that the powder should be dried to eliminate moisture. According to Niu et al [38], such a process increases the flowability of the powder.…”

“…Figure 4 presents a confocal image of a spherical alumina powder, similar to the raw material utilized in the already mentioned articles. The most used substrates in these processes were alumina [8][9][10]27,28,37] and the titanium alloy Ti-6Al-4V [29,30,32,34,38]. The thickness of alumina substrate varied between 3 and 50 mm, while substrates of Ti-6Al-4V with a thickness between 6 and 9 mm were employed.…”

“…The thickness of alumina substrate varied between 3 and 50 mm, while substrates of Ti-6Al-4V with a thickness between 6 and 9 mm were employed. The use of Ti-6Al-4V is due to its good compatibility and high laser absorptivity [29].…”