Perspective on pathways towards responsible surface engineering

In this perspective sustainability-relevant aspects of modern surface engineering technologies, which enable improved structural and functional surface properties, are critically evaluated. Although plasma-assisted physical vapour deposition (PVD) is increasingly employed to address global challenges, such as energy efficiency and reduction of CO 2 emissions, their inherently resource-intensive nature is often not considered. Surface engineering research should thus embrace sustainability-relevant aspects from a processes and materials design point of view. While we are convinced that sustainability-relevant surface engineering has to be based on synchronised process and materials solutions, we will discuss processes and materials separately. In terms of processes, we are going to describe the challenges of state-of-the-art technology, including energy and mass balances as well as product cycles. With respect to materials, the coating and process purity as well as chemical and microstructural complexity are discussed. Such approaches are fully in line with the United Nations Sustainable Development Goal 12 Responsible Consumption and Production . We expect that the here discussed urgently needed pathways towards responsible surface engineering will become important for the surface engineering community and adopted within the near future. Responsible surface engineering includes the human behaviour and necessitates a change in mindset of materials scientists and process engineers. Hence, two main questions are critically evaluated in this perspective: 1) What are sustainability-relevant aspects of PVD processes and materials? 2) Which pathways are available to move towards responsible surface engineering? • Responsible surface engineering includes ecological, economical and societal aspects. • Awareness for energy and mass balances as well as product cycles of PVD coatings. • Tolerable impurity levels of PVD processing reduce economical and ecological costs. • Chemically simple coatings reduce usage of critical raw materials. • Ecological footprint and energy consumption of research in surface engineering.