Materials World Network: LIGA Ni-base superalloys for MEMS applications
Final Report Abstract
Nickel is one of the most electrodeposited structural materials for Micro Electrical Mechanical Systems (MEMS). However, nickel’s mechanical properties degrade at high temperatures due to microstructural instabilities. New requirements for MEMS capable of operating in harsh and abrasive high temperature environments require the development of new LIGA materials, which may create also a wide range of new applications for MEMS. Nickel-aluminum superalloys are well known for their use in the hot stages of air plane engines because they show excellent high temperature mechanical properties. In this work, the electrodeposition of Ni with Al particles yielding composite coatings received extensive attention because it provides - with a following heat treatment - a simple and low cost way to produce Nickel superalloy coatings. The aim of this project is the development of thermally stable LIGA Ni-Al materials for high temperature MEMS applications. LIGA Ni-Al foils for thermally stable LIGA materials were electrodeposited with different compositions ranging from 4 to 10 at% aluminum in a nickel sulfate electrolyte with added aluminum nano particles. For stabilization of the aluminum particles in the electrolyte, the effect of different additives was tested. The influence of process conditions on the composition and properties of the material was analyzed. The as-deposited coatings show a nearly uniform distribution of Al particles in the material. To create the γ’-phase, the received Ni-Al layers were solutionized at high temperatures (900°C- 1100°C) and annealed (500°C-750°C) for different durations. Their microstructures were then analyzed and compared with those before annealing and those of pure LIGA nickel subjected to the same heat treatment. Prior to heat treatment, the observed microstructures show a finer grained microstructure compared to the pure LIGA nickel. After heat treatment the grain size is increased and the aluminum is dissolved in solid solution with small phase precipitations. For material characterization, Ni-Al micro tensile testing samples and TEM discs were electrodeposited. The as-deposited micro tensile testing samples were then heat treated and tested at room temperature and elevated temperatures using a testing machine for micro tensile and micro creep testing to determine their mechanical properties. Here, the heat treated Ni-Al samples show significantly improved thermal stability compared to the annealed LIGA nickel samples.
Publications
- Entwicklung von galvanisch abgeschiedenem LIGA-Ni-Al für Hochtemperaturanwendungen, Proceeding of MikroSystemTechnik – KONGRESS 2011, Darmstadt, Oct. 2011
M. Teutsch, J. Aktaa, D. E. Burns, K. J. Hemker, K. Bade
- Development of Ni-based superalloys for microelectromechanical systems, Scripta Materialia 67 (2012) 459-462
D.E. Burns, Y. Zhang, M. Teutsch, K. Bade, J. Aktaa & K. Hemker
(See online at https://doi.org/10.1016/j.scriptamat.2012.06.003) - Processing and Characterization of Ni-base Superalloy Microcomponents and Films for MEMS Applications, PhD Thesis, Oct. 2012
D.E. Burns
- Entwicklung von elektrochemisch abgeschiedenem LIGA-Ni-Al für Hochtemperatur-MEMS-Anwendungen, Dissertation, März, 2013
M. Teutsch
