Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2022
Thesis Language: English
Student: MOHAMED EID SAIED ABDELMOULA
Supervisor: Gökhan Küçüktürk
Abstract:
Direct-Powder Bed Selective Laser Processing (D-PBSLP) is considered a promising technique for Additive Manufacturing (AM) of Ceramic materials. To be successful in the D-PBSLP of ceramic materials, it is necessary to use the proper values for the process parameters. A numerical model has been developed to obtain the proper process parameters for successful D-PBSLP of ceramic materials to be used as a guide through the experimental investigation. Alumina and SiC were used as model materials in this study. Using the developed numerical model in the PBSLP investigation of multilayer scanning with different build orientations reveals that the build orientation and scanning strategies are essential for controlling the printed samples' developed thermal stress and cracking. For D-PBSLP alumina, the Linear 45° scanning strategy produced the most promising results compared to other investigated scanning strategies. In addition, by using a high scanning speed of 400 mm/s, it was possible to print alumina samples of high quality, as measured by a high relative density of 85 %, compared to 100, 200, and 300 mm/s. After determining the optimal scanning strategies, scanning speed, and other parameter values as predicted by the numerical mode, the process parameters were optimized using the Taguchi optimization method and Paetro ANOVA analysis. Laser power of 210 W, scanning speed of 400 mm/s, and hatching space of 30 µm were the optimal process parameter settings for printing alumina samples with a high density of 94.5 %. Utilizing the compressive test and microhardness measurement, the mechanical performance was evaluated. The tested samples yielded a microhardness value of 2180 HV, identical to the value reported in the literature. In contrast, the obtained compressive strength was approximately 140 MPa, which is low compared to the values reported in the literature. The same procedure was followed while investigating D-PBSLP of SiC. The scanning strategies investigation concluded that the inclined zigzag scanning strategy is recommended for D-PBSLP of SiC, as it overcomes nearly all of the obstacles encountered by the other investigated scanning strategies. Then the scanning speed considering different values such as 100, 250, and 500 mm/s with different layer thicknesses of 22, 30, and 40 µm. Using low scanning speeds and low layer thicknesses, such as 22 and 30 µm, it was possible to successfully print SiC samples with a relative density of 85 %, as demonstrated by the results. Attaining a relative density of 87 % required optimization of the process parameters, resulting in a laser power of 45W, a scanning speed of 100 mm/s, and a hatching space of 40 µm. The mechanical performance was evaluated using a compressive test, which revealed a low compressive strength of 1.4 MPa; consequently, postprocessing should be considered to enhance the mechanical performance.
Key Words : Additive manufacturing, ceramics, numerical analysis, laser |