Abstract
The measurement of cutting force is an effective method for machining condition monitoring in intelligent manufacturing. Titanium nitride films and silicon nitride films were prepared on 304 stainless steel substrates by DC-reactive magnetron sputtering and plasma-enhanced chemical vapor deposition (PECVD). The effects of substrate negative bias and nitrogen flow on the surface microstructures of TiN film were investigated. The smoothness of the film is optimal when the bias voltage is −60 V. X-ray diffraction (XRD) analysis was performed on the samples with the optimal smoothness, and it was found that when the nitrogen flow rate was higher than 2 sccm, the titanium nitride film had a mixed phase of TiN(111) and (200). It is further revealed that the change of peak intensity of TiN(200) can be enhanced by nitrogen flow. Through atomic force microscopy (AFM), it is found that the stronger the intensity of the TiN (200) peak, the smoother the surface of the film is. Finally, the effect of different film thicknesses on the hardness and toughness of the TiN/Si3N4 film system was studied by nanoindentation experiments. The nanohardness (H) of the TiN/Si3N4 film can reach 39.2 GPa, the elastic modulus (E) is 480.4 GPa, the optimal toughness value (H3/E2) is 0.261 GPa, and the sample has good insulation performance. Linear fitting of the film’s toughness to nanohardness shows that TiN/Si3N4 films with higher hardness usually have a higher H3/E2 ratio.
Highlights
Veprek et al proposed the concept of crystalline–amorphous nanocomposite coating by modifying transition metal (TM) nitride [8,9,10,11], in which the most typical composite structure is the nc-TiN/α-Si3 N4 thin-film system
The evolution of the surface microstructures of the films is shown in the atomic force microscopy (AFM) images
When the nitrogen flow rate is greater than 2 sccm, the re-sputtering effect occurs at −40 V, resulting in a decrease in film thickness and deposition rate
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. A thin-film strain cutting force sensor is widely used because of its high precision and reliability [4,5,6,7]. Much research has been devoted to studying the microstructure and tribological behavior of TiN/Si3 N4 thin films, few studies have been carried out on their application in the field of cutting force sensors. If the film system is applied to the cutting process of high-strain rate-impact, the all-around performance of hardness and toughness becomes an important index, which is essential for improving the measurement accuracy and service life of the sensor.
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