Powder Metallurgical Processing of MMC Pressure Springs Based on Zirconia and TRIP Steel

A novel powder metallurgical fabrication technology for the development of springs based on metastable austenitic steel and magnesia partially stabilized zirconia is introduced. The developed gel casting technique uses the gelation of alginates in contact with bivalent ions and allows the variation of fabrication parameter such as composition of the starting slurry, wire thickness, coil number, and distance between the single coils. The starting slurry contains 16‐7‐3 (Cr–Mn–Ni) steel and zirconia powders as well as sodium alginate and is subsequently injected into a hardener solution to form rubbery strands that are subsequently coiled around a mandrel to form a spring element. Afterward a two‐stage thermal process is performed. The sintered spring elements are characterized by a homogeneous microstructure, and the formation of manganese silicate is registered. In comparison to commercially available coil springs, the developed spring elements show similar deformation behavior up to a deformation of 50%. The composition which contains 10 vol% zirconia and 90 vol% steel particles shows an improved energy absorption capability with 0.19 kJ kg⁻¹ compared with commercially available springs with 0.11 kJ kg⁻¹, and therefore offers the potential for further investigations in the planned application in the area of crash absorbing structures.