Titanium nitride (TiN) was vacuum deposited onto M2 tool steel and tungsten carbide (WC) substrates by reactive magnetron sputtering. The purpose of this experiment was to vary the substrate bias to optimize the density, residual stress and hardness of the TiN surface layer. Hardness was determined from unloading curves of nanoindentations. Contact mode atomic force microscopy reveals columnar TiN grains with bimodal diameter distribution (80 nm and 300 nm). Residual stress was determined by x-ray diffraction. For identical deposition conditions, TiN coating on M2 steel is consistently harder than the coating on WC and has larger compressive residual stress. On identical substrates, the three deposition conditions, however, produce coatings that within the experimental precision have nearly the same hardness and residual stress.