Small atoms as reinforced agent for both hardness and toughness of Group-VIB transition metal films

Abstract The work associated with simultaneous enhancement in the hardness and toughness is filled with challenge but significance. Here, we succeeded in dealing with this question based on Group- VIB transition metals (W, Mo and Cr), and presented a universal phenomenon that highly hard yet toughened transition metal films can be obtained by doping few small atoms. Our results indicated that the introduced low-concentration (∼6 at. %) small atoms (C or B) by magnetron co-sputtering, in the doping regime, could form supersaturated solid solution and lead to significantly increased hardness (∼2 × higher), which is comparable to their ceramic compounds. Simultaneously, exceptional metallic toughness can also be obtained in this way. Dopants induced refined grains (fine-grain strengthening), lattice distortion (solid-solution strengthening), higher compressive stress and H / E ∗ (hardness/effective elasticity modulus) contribute to such surprising combination of enhanced hardness and toughness (crack resistance). This method is expected to be applicable for the transition-metal-based protective coatings. Better yet, it is featured with higher efficiency and low cost.