Textured WO3 and WO3:Mo films deposited from chemical solution on stainless steel

Tungsten trioxide (WO3) and molybdenum-doped tungsten trioxide (WO3:Mo) films were deposited on stainless steel surface by a chemical aqueous solution approach using dip-coating technique. The deposited 5, 10 and 15-layer films were homogeneous and continuous. The surface morphology and crystallinity of the produced films were dependent on the metal cation species and concentration of PVA in the solution. FE-SEM analysis revealed the formation of textured WO3 film surfaces having spike-like nanostructures. The values of the static water contact angle measured on the film surface showed that deposited WO3 films can exhibit both hydrophilic and hydrophobic nature, while WO3:Mo films showed hydrophilic behavior. Tribological properties of the deposited films were evaluated in deionized water. All three coatings retained a lubricating layer much better than original steel, demonstrating major reduction in friction and wear. Particularly effective were PVA-free WO3 films, whose friction coefficient stayed under 0.2 for over 2000 cycles. Excellent tribological, hydrophobic and hydrophilic properties along with simple deposition methods suggest very promising potential of WO3 and WO3:Mo coatings in industrial applications.