Influence of Si doping on the microstructure and hardness of an AlTiSiN coating deposited by low pressure chemical vapor deposition

Abstract

The effect of Si doping on the microstructure and hardness of an AlTiSiN coating deposited by the low pressure chemical vapor deposition (LPCVD) method was studied in detail using grazing incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and a nanoindenter instrument. The results show that Al0.82Ti0.18N coating exhibits a typical columnar crystal structure, while Al0.88Ti0.09Si0.03N and Al0.82Ti0.08Si0.10N coatings show a fine equiaxed crystal structure. The number of internal substructures (dislocation, stacking fault, etc.) decreased, while the volume fraction of the amorphous structure increased with the increase of Si content. The results of GIXRD and HRTEM show that all AlTiSiN samples mainly consist of fcc AlN phase with a small amount of hcp AlN phase. Furthermore, a small amount of fcc TiN phase can only be observed in Al0.82Ti0.08Si0.10N coating. The hardness of Al0.82Ti0.18N, Al0.88Ti0.09Si0.03N, and Al0.82Ti0.08Si0.10N coatings is 33.0 ± 0.6 GPa, 38.3 ± 1.2 GPa and 27.0 ± 0.8 GPa, respectively. Al0.88Ti0.09Si0.03N coating has obvious potential value for industrial applications.