AbstractCold plasma technology has enabled the development of a new generation of low-temperature (450°C or less) thermochemical surface treatments for stainless steels. This chapter describes how the technology is used. By varying the process parameters, it is possible to synthesize a variety of layered structures, and, in particular, to produce hard, precipitate-free layers based on the expanded austenite lattice. The diffusion elements can be nitrogen, carbon, or nitrogen and carbon. In this chapter, we examine the different metallurgical structures and their main characteristics in terms of wear and corrosion resistance.