An open-system irreversible thermodynamic analysis on inert wear and attrition is presented. The aim is to derive a theory which may be implemented in computational fluid dynamics flow solvers. In order to conduct analysis on the differential scale, it is shown that traditional macroscopic-scale concepts, earlier well-established in the literature, cannot be immediately applied. Hence, new differential concepts are introduced. It is argued that the overall analysis can be split up into sub-processes, where different types of specific sub-processes of wear and attrition may be extracted, and directly connected with the corresponding breakage or deformation of either ductile- or brittle-type target materials. Applying the residual thermodynamics framework, the new concepts of wear work and attrition work (at adiabatic conditions) can be defined, which typically only represent a small – often negligible – fraction of the total work.