新型Ti-Si-C-N纳米复合超硬薄膜的高温热稳定性

用脉冲直流等离子体辅助化学气相沉积（PCVD）方法在高速钢基体上沉积出新型Ti—Si—C—N超硬薄膜．Ti—Si—C—N薄膜为纳米晶／非品复合结构（nc—Ti（C，N）／a-Si3N4／a-C—C），当薄膜中Si和C含量较高时，Ti（C，N）转变为TiC，晶粒尺寸减小到2—4nm．薄膜晶粒尺寸和硬度的高温热稳定性均随沉积态薄膜中的原始晶粒尺寸减小而提高，当原始晶粒尺寸在8—10nm之间时，晶粒尺寸和硬度热稳定性可达900℃；当原始晶粒尺寸在2—4nm之间时，晶粒尺寸和硬度热稳定性可达1000℃．薄膜硬度和晶粒尺寸表现出同步的高温热稳定性．分析认为由调幅分解形成的纳米复合结构中的非晶相强烈地抑制晶界滑移与晶粒长大，从而使Ti—Si—C—N薄膜的热稳定性显著提高．

Thermal Stability of A Novel Ti-Si-C-N Superhard Nanocomposite Coating at Elevated Temperature

Superhard nanocomposite Ti-Si-C-N coatings were deposited on substrate of high speed steel using an industrial pulsed d.c. plasma chemical vapor deposition set-up. Dependence of Si and C contents and annealing at elevated temperatures on the microstructure and hardness of Ti-Si-C-N coatings were investigated. Detailed microstructure examined by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) suggested that the Ti-Si-C-N coatings was a nanocomposite structure composed of nanocrystalline Ti(C,N) and amorphous carbon and Si3N4. And the crystalline size and microhardness of coatings showed high thermal stability even at 1000° C when Si and C contents were higher of 12.1 at.% Si, 32.9 at.% C. The possible origin of high thermal stability of superhard nanocomposite Ti-Si-C-N coatings is explained by spinodal decomposition that occurs during deposition.