This project establishes a science-based protocol for optimizing processing and heat treatment routes to produce a new class of materials (electrodeposited Ni-base superalloys) that will dramatically improve the functionality of electrodeposited LIGA materials. An international research team from Johns Hopkins University (JHU) and the Karlsruhe Institute of Technology (KIT) collaborate on this task. Overarching scientific issues addressed by this team include: (i) control and optimization of electrodeposition parameters to uniformly entrain Al nano-particles in electrodeposited Ni micro-components, (ii) development of heat treat schedules required to transform the as-deposited green composites into ?×?{?ס¦ superalloy microstructures, and (iii) characterization of the resultant microstructures and attendant mechanical properties. Close interaction of the research groups allows for optimization of the process flow and result in the creation of novel high temperature LIGA electrodeposited Ni-base superalloys for MEMS applications.
The technological motivation for this collaboration is derived from the opportunity to expand the temperature capability of current MEMS materials. To date, the majority of commercial MEMS devices have been thin film sensors manufactured using chemical and vapor deposition processes. The availability of LIGA Ni-base superalloys would greatly expand the design space for next generation MEMS devices. Development of a process flow for electrodeposition of Ni-base superalloys will also lay the foundation for electrodeposition repair strategies that would provide tremendous technological and economic advantage in the repair of turbine blades for both jet propulsion and power generation. International exchanges of graduate students and senior personnel fuel and enable this collaboration and provide a unique educational experience for all participants. Moreover, the proposed inclusion of Baltimore city high school students through mentoring at JHU and a foreign visit to KIT will greatly expand their academic and cultural horizons.
Research – Our collaborative research team pursued three parallel processing routes aimed at developing MEMS-compatible processing routes for the production of Ni-base superalloy micro-structures and thin films. With our assistance, collaborators at the Karlsruhe Institute of Technology (KIT) developed electroplating protocols for the formation of Ni-Al MEMS alloys by entraining Al nanopowders into electrodeposited Ni films and MEMS structures. Two processing routes were pursued at Johns Hopkins University (JHU), and both of these routes proved successful in producing two-phase precipitation strengthened microstructures characteristic of modern Ni-base superalloys. The first of these employed vapor phase aluminization to add Al to a freestanding LIGA Ni micro-component resulting in a layered sequence of Ni-Al intermetallic phases. A subsequent homogenization heat treatment was developed and used to distribute the Al throughout the component producing a cuboidal Ni-Ni3Al microstructure. The second technique involved magnetron sputtering of a commercial nickel-base superalloy (alloy 718) onto Si and brass substrates. In addition to material processing, a thorough understanding of the precipitation behavior of these novel materials was investigated via microstructural observations on as fabricated and heat-treated materials. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), wave dispersive spectroscopy (WDS), and energy dispersive spectroscopy (EDS) were employed and microstructural features were linked to mechanical properties by performing room and elevated temperature micro-tensile experiments at JHU and KIT. In an effort to expand existing high temperature micro-tensile testing techniques, a new high temperature micro-tensile load frame, incorporating a displacement-based force sensor, was designed and constructed at JHU. Outreach - This Materials World Network Program was specifically designed to provide doctoral students from JHU and KIT with extended internships at the partnering institutions. The four 2-month internships that were conducted greatly facilitated the research but also afforded the participants an opportunity to experience a foreign culture both in the laboratory and in everyday life. Moreover, involvement of Hopkins undergraduates and high school students from Baltimore Polytechnic in this research project successfully motivated these students to pursue their own engineering careers. JHU graduate student Devin Burns defended his Ph.D. in November 2012 and is currently employed at NASA Goddard. KIT graduate student Michael Teutsch is now a teaching-track professor in Germany. Two high school students from Baltimore Polytechnic, Devin Burns and Joshua Greenspan, conducted yearlong research internships at JHU and are currently engineering undergraduates at MIT and the University of Maryland, respectively.
