Abstract
Austenitic steels are characterized by their outstanding corrosion resistance. They are therefore suitable for a wide range of surface protection requirements. The application potential of these stainless steels is often limited by their poor wear resistance. In the field of wrought alloys, interstitial surface hardening has become established for simultaneously acting surface stresses. This approach also offers great potential for improvement in the field of coating technology. The hardening of powder feedstock materials promises an advantage in the treatment of large components and also as a repair technology. In this work, the surface hardening of AISI 316L powder and its processing by thermal spraying is presented. A partial formation of the metastable expanded austenitic phase was observed for the powder particles by low-temperature gas nitrocarburizing. The successful deposition was demonstrated by cold gas spraying. The amount of expanded austenitic phase within the coating structure strongly depends on the processing conditions. Microstructure, corrosion and wear behavior were studied. Process diagnostic methods were used to validate the results.
Highlights
The excellent corrosion resistance of stainless steels contributes to several wide-ranging surface protection applications
AISI 316L powder reveals the detection of the expanded austenitic phase
The results show that the direct transfer of existing treatment routines to powder materials is impossible
Summary
The excellent corrosion resistance of stainless steels contributes to several wide-ranging surface protection applications. In order to provide adequate surface protection under superimposed stresses, the property profile of these materials can be improved by solution hardening. For applications where an adequate corrosion resistance is required, interstitial hardening is preferred over precipitation hardening. The elemental enrichment of the surface layer results in strong compressive residual stresses [3]. A significant increase in hardness and wear resistance is achieved. A successful enrichment has already been demonstrated in wrought alloys [1,2,3]. The first results on precipitation hardening by thermochemical treatment of thermal spray coatings were obtained by Nestler et al, while
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