Abstract
A solution-hardening of AISI 316L stainless-steel powder was conducted. The expansion of the crystal lattice and a strong increase in the nanoindentation hardness confirm the successful diffusion of carbon and nitrogen in the interstices. A multiphase state of the powder feedstock with phase fractions of the metastable S-phase (expanded austenite) mainly at the particle’s edge, and the initial austenitic phase within the core was found. Thermal spraying using high velocity oxy-fuel (HVOF) and atmospheric plasma spraying (APS) prove the sufficient thermal stability of the Sphase. Microstructural investigations of the HVOF coating reveal the ductility of the S-phase layer, while the higher heat load within the APS cause diffusion processes with the initial austenitic phase. The lattice expansion and the nanoindentation hardness decrease during thermal spraying. However, the absence of precipitates ensures the sufficient heat stability of the metastable S-phase. Even though further efforts are required for the thermochemical treatment of powder feedstock, the results confirm the feasibility of the novel powder treatment approach.
Highlights
Even though further efforts are required for the thermochemical treatment of powder feedstock, the results confirm the feasibility of the novel powder treatment approach
The corrosion resistance of austenitic stainless steel has contributed to the wide range of high-performance applications of this material group
Thermal spraying was performed on stainless-steel AISI 316L substrates
Summary
The corrosion resistance of austenitic stainless steel has contributed to the wide range of high-performance applications of this material group. Despite their excellent corrosion resistance, the low wear resistance restricts possible applications. Surface hardening by thermochemical treatment is suitable to enhance the material’s performance. Producing coatings by thermal spraying can be used for various substrate materials, because of their comparatively low heat load. The limited thermal stress efficiently prevents the formation of precipitates of the metastable S-phase, and enable repair applications of worn surface parts. A successful S-phase formation of the thermal spray coatings by thermochemical post-treatment was first reported by Wielage et al [7]. Further investigations by Adachi et al and Lindner et al prove the general feasibility of coating treatment by low-temperature thermochemical
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