TiN, TiC, ZrN, ZrC, HfN, and HfC coatings were reactively sputtered at high rates of 2300 –5800 Å/min onto T‐15 high speed steel cutting tool inserts. Nitrogen was controlled through closed loop peak feedback control for the preparation of the nitride coatings, but either peak feedback control or flow control could be used for the carbide coatings. Methane was the reactive gas for TiC and ZrC, but it led to macrovoids in HfC. Acetylene produced dense HfC coatings. All of these coatings are much harder than the values for the bulk materials.Hafnium nitride was the hardest nitride with a Vickers microhardness (50 g) of 4690 kg/mm2, whereas ZrC was the hardest carbide with a hardness of 4840 kg/mm2. Except for TiC, all of the coatings have a lattice parameter that is greater than the bulk value. The coatings have the NaCl structure with a (111) preferred orientation. All of the coatings have an excellent adhesion to the T‐15 substrates, but a ZrN/Zr carbonitride interface was necessary with ZrC to obtain good adhesion. The ZrC and HfC coatings show an adhesion aging effect in which the adhesion increases with time. Vickers microhardness tests (50 g) show that ZrN and HfN have excellent hot hardness up through 800 °C, but at 1000 °C the hardness of HfN (440 kg/mm2) is much less than the hardness of ZrN (760 kg/mm2).