## 1 Introduction
Iron-based coatings are becoming increasingly important as an environmentally friendly alternative to conventional WC-Co and WC-Co-Cr coatings. Recent studies show that, as well as offering advantages in terms of sustainability and resource conservation, they also reveal promising potential in terms of wear resistance and performance [33]. Alternative coating systems such as TiC-Ni\({}_{3}\)Al are frequently investigated in efforts to reduce the use of WC-based coatings. This type of coating provides comparable wear resistance to that of conventional WC-Co-Cr layers and is therefore considered a promising alternative [9]. Recently, NbC-FeCr-based coatings have also come into focus. The base material is easy to apply and has comparable wear resistance to WC-Co-Cr systems, as is particularly evident in similar dry-running wear rates [27]. Another approach involves the recycling of WC-Co-Cr/WC-Co materials. These processes are often complex and economically viable mainly for larger companies. Nevertheless, they offer a significant ecological advantage over extracting and processing tungsten from primary raw materials generated through weathering in the atmosphere. For instance, recovery rates of over 80% can be achieved with W/WC. Globally, the re cycling rate stands at around 46% [30; 34]. The relevance of recycling is also highlighted by the analysis of CRM recycling rates in relation to meeting EU demand. Tungsten and cobalt are among the most frequently recycled critical raw materials, surpassed only by vanadium [35]. Currently, WC and Co recycling focuses primarily on hard metal scrap, such as that from worn-out drilling tools. So far, coatings have played only a minor role in the recovery process [34; 36]. The production of primary tungsten carbide involves several steps and long supply chains. In contrast, recycling WC and W waste is significantly more environmentally friendly as the required energy input is mostly limited to electricity and chemicals [37]. Recycled WC waste (secondary tungsten carbide) is partly processed into fine powders suitable for subsequent sintering processes, but its use in combination with HVOF has not yet been widely explored [38; 39]. A largely unexplored method in the field of thermal spraying is the reuse of filter dust. This refers to material that has passed through the entire spraying process, but which did not adhere to the component surface. This so-called overspray is extracted and collected in a filter container. The proportion of overspray can account for up to 20% of the feedstock powder [40]. Additionally, there is actual loss due to the sublimation of small powder particles. Various studies have investigated deposition efficiency, which is defined as the ratio of deposited to consumed material. This rate varies significantly depending on the material and process, typically ranging from 40 to 75%, and rarely exceeding 85 to 90% [40; 41; 42; 43]. This suggests that there is untapped potential within thermal spraying as filter dust could be reused for future coating processes. The goal of this research was to apply an HVOF sprayed coating made from recycled filter dust consisting of around 80% WC-Co or WC-Co-Cr. A conventional HVOF sprayed WC-Co-Cr coating served as a reference. The coating made from recycled material is also intended to provide wear and corrosion protection for industrial applications. To this end, its various mechanical properties, microstructure, sliding wear behavior, and corrosion resistance in marine and acidic environments were analyzed. The results were evaluated and discussed in an overall context.