Selective Laser Melting Based Additive Manufacturing of Multiple Metallic and Functionally Graded Materials

  • Chao Wei

Student thesis: Phd

Abstract

Production of multiple material components and functionally graded materials (FGM) is desirable to tailor material properties at different locations. However, this is very challenging using conventional processes and existing additive manufacturing (AM) technologies. Current metal AM technologies are limited to producing single material and vertical FGM parts, i.e., a different material composition in different layers, but not within the same layer. This research aimed to develop and evaluate a new multiple material selective laser melting (SLM) AM technology for the fabrication of multiple material components and horizontal/3D FGM components. The objectives included: i) to develop a new selective, point-by-point powder deposition system to dispense multiple material powders combined with powder bed spreading, ii) to understand the feasibility and characteristics of combined powder bed system and selective powder delivery in selective laser melting additive manufacturing of multiple material components, iii) to understand factors affecting the packing density in laser fusion of ultrasonic deposited powder layers, iv) to demonstrate 3D printing of functionally graded components using the system, v) to develop a ceramic-metal composite as the support material for selective laser melting, vi) to apply the new multiple material additive manufacturing for anti-counterfeiting of metallic component manufacture. A new multiple material SLM system was successfully developed to realise the above objectives. Such a system could deposit up to 7 types of distinct powder materials on the same powder layer. A novel dual vibration ultrasonic powder delivery system was developed and integrated with a powder bed based selective laser melting system, together with a selective single layer point-by-point powder removal system to realise the multiple material 3D printing. The characteristics of such a system were investigated, and higher porosity was found in ultrasonically deposited parts. It was improved by introducing selective powder compression approach. Horizontal FGM and three dimensional (3D) FGM components made up of different 316L/Cu10Sn compositions were manufactured successfully using the multiple material SLM system. It also showed that the maximum hardness lies in the region comprised of 50 vol% 316L and 50 vol% Cu10Sn. The system can be used for rapidly developing new alloying systems and understanding their characteristics. In the selective laser melting process, a significant barrier for high productivity is the need for removal of support materials that are typically required in the manufacturing of 3D metallic components. Previously the support material is the same as the build material. Their removal is thus a time-consuming and impossible for internal structures. In this research, a new approach was investigated. The experimental results showed that a SiC-316L composite with 40 vol% 320 grit SiC was feasible to be applied as a support material for 316L stainless steel component additive manufacture using the multiple material SLM, which made easy removal, resulting from the brittle ceramic-metal composition phase induced cracks. In critical aerospace and medical products, preventing counterfeiting is highly desirable to avoid loss of lives. The above AM system was successfully applied to embedding Cu10Sn tagging safety features into SLM processed 316L components for the first time. Safety features at up to 15 mm embedding depth could be identified by X-ray imaging and X-ray fluorescence imaging. A criterion for embedding material selection was proposed.
Date of Award1 Aug 2019
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorLin Li (Supervisor), Zhu Liu (Supervisor) & Wei Guo (Supervisor)

Keywords

  • non-destructive inspection
  • embedded security features
  • Anti-counterfeiting
  • support structure
  • SiC-316L composite
  • powder bed fusion
  • porosity
  • functionally graded materials
  • packing density
  • powder compression
  • additive manufacturing
  • selective laser melting
  • 3D printing
  • Ultrasonic powder dispensing
  • multiple material

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