Researchers from Iowa State University, South Dakota School of Mines and Technology, VRC Metal Systems, and the U.S. Army Research Laboratory discussed the feasibility of forming martensitic coatings with tailored strength and ductility by cold-spraying austenitic steel powders.
The technology was evaluated by analytical, numerical, and experimental studies. The fraction of martensite transformed in cold-sprayed 316L austenitic stainless steel varied from 3.4% to 36.0%, depending on the process parameters. The remaining austenite could provide ductility and more strength by transformation-induced plasticity upon subsequent severe loadings.
Volume expansion by martensitic transformation will increase the level of residual compressive stresses in the cold-sprayed coating, which enhances the resistance to stress corrosion cracking.
This study confirms that martensitic coatings with tailored strength, hardness, ductility, and residual stresses can be readily formed by cold spray of austenitic steel powders. Such functional martensitic coatings can be utilized for surface coatings or repairs of structural parts susceptible to wear or cavitation erosion such as hydraulic turbine parts and propellers.
Jonghyun Lee, Cal Wong, Iowa State University;
Morotolaoluwa Alabi,, South Dakota School of Mines and Technology;
Christian Widner, VRC Metal Systems;
Dennis Helfritch, Victor Champagne, U.S. Army Research Laboratory
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