A multi-position rotary shear valve assembly having a substantially metallic or ceramic stator device and a substantially metallic or ceramic rotor device. The stator device defines a substantially planar stator face and at least two or more stator channels in fluid communication with the stator face at corresponding stator ports, while the rotor device includes a substantially planar rotor face defining one or more rotor channels. A tribological coating is disposed atop at least one of the rotor face and the stator face, which enables a substantially fluid-tight, selective relative rotation between the rotor face and the stator face, at a rotor-stator interface, between two or more rotor positions.