(Ti,W,Cr)B2 coatings produced by dc magnetron sputtering

Transition metal diboride coatings of composition (Ti0.44W0.29Cr0.27)B1.90 were deposited on silicon substrates by dc magnetron sputtering of compound targets. The chemical composition of the targets is transferred to the sputtered films. The as-deposited films are amorphous as indicated by grazing incidence X-ray diffraction. Investigations with electron microscopy revealed that the films show a columnar nano-structure. Annealing at temperatures between 1000 °C and 1300 °C leads to the formation of nano-crystalline precipitations, which can be attributed to (Ti,W,Cr)B2, β-(W, Ti, Cr)B and W2B4 phases. Annealing can be used to tailor the average grain size of the precipitates, making these films a good candidate for hard coatings re-enforced by nano-structuring.