Comparative study on microstructure and properties of nanocrystal and amorphous W–Si–B coatings

Crystalline and amorphous W–Si–B coatings with different Si contents were fabricated by magnetron sputtering. The influence of Si content on microstructure, mechanical and tribological properties of the coatings was evaluated. The results reveals that the crystalline W–Si–B coatings are nanocomposite structures consisting of nanocrystalline AlB2-type WB2 grains and amorphous Si/Si3N4. Crystalline coatings with Si content of 4.7 at.% exhibits the maximum hardness of 35.8 GPa and better fracture toughness compared with pure WB2 coating, leading to the lowest wear rate of 1.3 × 10−7 mm3/Nm. As for the amorphous W–Si–B coatings, the lower hardness of the coatings tends to lead to excellent fracture toughness, which gives rise to the low wear rate. The different enhancement mechanisms of both types of coatings are discussed in detail.