Turning continues to be the largest segment of the machining industry, which highlights the continued demand for turned parts and the overall improvement of the process. The turning process has seen quite an evolution, from basic lathes using solid tools, to complex CNC (Computer Numerical Control) multi-process machines, using, for the most part, coated inserts and coated tools. These coatings have proven to be a significant step in the production of high-quality parts and a higher tool life that have captivated the industry. Continuous improvement to turning coated tools has been made, with many researches focusing on the optimization of turning processes that use coated tools. In the present paper, a presentation of various recently published papers on this subject is going to be made, mentioning the various types of coatings that have recently been used in the turning process, the turning of hard to machine materials, such as titanium alloys and Inconel, as well as the interaction of these coatings with the turned surfaces, the wear patterns that these coatings suffer during the turning of materials and relating these wear mechanisms to the coated tool’s life expectancy. Some lubrication conditions present a more sustainable alternative to current methods used in the turning process; the employment of coated tool inserts under these conditions is a current popular research topic, as there is a focus on opting for more eco-friendly machining options.

https://www.mdpi.com/2075-4701/10/2/170/pdf

Recent Advances in Turning Processes Using Coated Tools—A Comprehensive Review

Due to the increasing maintenance costs of hydraulic machines related to the damages caused by cavitation erosion and/or erosion of solid particles, as well as in tribological connections, surface protection of these components is very important. Up to now, numerous investigations of resistance of coatings, mainly nitride coatings, such as CrN, TiN, TiCN, (Ti,Cr)N coatings and multilayer TiN/Ti, ZrN/CrN and TN/(Ti,Al)N coatings, produced by physical vapor deposition (PVD) method using different techniques of deposition, such as magnetron sputtering, arc evaporation or ion plating, to cavitation erosion, solid particle erosion and wear have been made. The results of these investigations, degradation processes and main test devices used are presented in this paper. An effect of deposition of mono- and multi-layer PVD coatings on duration of incubation period, cumulative weight loss and erosion rate, as well as on wear rate and coefficient of friction in tribological tests is discussed. It is shown that PVD coating does not always provide extended incubation time and/or improved resistance to mentioned types of damage. The influence of structure, hardness, residence to plastic deformation and stresses in the coatings on erosion and wear resistance is discussed. In the case of cavitation erosion and solid particle erosion, a limit value of the ratio of hardness (H) to Young’s modulus (E) exists at which the best resistance is gained. In the case of tribological tests, the higher the H/E ratio and the lower the coefficient of friction, the lower the wear rate, but there are also many exceptions.

Resistance of PVD Coatings to Erosive and Wear Processes: A Review

The TiAlSiN/Cr multilayer coatings with different thicknesses of chromium (Cr) layers were designed and prepared by high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) for the improvement of their solid particle erosion and corrosion resistance. The structure-property relationship was investigated by the systematic characterization of the microstructure, hardness, Young's modulus, toughness, solid particle erosion resistance, and corrosion properties of those coatings. The results reveal that the TiAlSiN layers consisted of the TiN crystalline phase and amorphous phase. As the Cr layers thickness increased, the grain growth of the Cr layers was columnar with a strong Cr (110)-preferred orientation. Compared with the TiAlSiN coating, the TiAlSiN/Cr multilayer coatings showed significantly improved toughness and corrosion performance. The toughness, H/E ratio, erosion resistance at impact angle of 90°, and corrosion resistance of the TiAlSiN/Cr multilayer coatings firstly increased when the Cr layer thickness increased up to 21 nm, before decreasing with a further increase of Cr layer thickness. Our results show that the TiAlSiN/Cr multilayer coatings with the Cr layer thickness of 21 nm exhibit enhanced toughness, excellent erosion resistance, and corrosion resistance together with high hardness.

Improvement of solid particle erosion and corrosion resistance using TiAlSiN/Cr multilayer coatings

Effects of specific surface area of electrode and different electrolyte on capacitance properties in nano porous-structure CrN thin film electrode for supercapacitor

Microscratch of copper by a Rockwell C diamond indenter under a constant load

Micro-nano multilayer structure design and solid particle erosion resistance performance of CrAlNx/CrAlN coating

The thin-film electrode for supercapacitors has broad prospects for providing high energy storage capacity. However, the microstructure of dense film resulting in poor ion access limits its capacitance still far below the theoretical value. Here, CrN thin film electrodes with good cycle performance can be prepared by tuning the porosity of the film at the nanoscale level. The atomic diffusion process and atomic peening effect that occur during the sputtering process of chromium nitride are the pivotal parameters for generating porosity and high specific surface area. During the controlled sputtering process, an increase in the nitrogen flow rate causes an increase in the porosity in each column (intracolumnar porosity), while an increase in temperature controlling the gap between two columns (intercolumnar porosity). When the nitrogen flow rate is 10 sccm and the deposition temperature is 250 °C the CrN film has the areal capacitance of 41.7 mF cm−2, 10 mV s−1 at the thickness of 950 nm. In addition, the CrN film has good electrochemical cycling stability, the capacity retention rate is still as high as 93.2% after 20,000 cycles. Therefore, the CrN film electrode has a promising application prospects in energy storage systems such as supercapacitors.

Sputtered chromium nitride films with finely tuned intra- and intercolumnar porosities as pseudocapacitive electrode for supercapacitors

Thermal stabilization of nanocrystalline promoting conductive corrosion resistance of TiN–Ag films for metal bipolar plates

The phase constituents and mechanical properties of Cr/CrAlN and Cr/CrN/Cr/CrAlN coatings which prepared by Arc Ion Plating were investigated in this work. The stress variation of the coating process was investigated by the finite element method and the failure mechanism of the coatings was analyzed. The results suggested that the, Cr/CrN/Cr/CrAlN coating have fewer surface micro-particles, higher adhesion strength (86.7 ± 2.1 N), and lower residual stress (−1.665 ± 0.042 GPa) compared with Cr/CrAlN coating. In addition, the erosion resistance performance of the multilayer coatings is obviously higher than that of the uncoated specimen. According to crack growth and stress analysis, it is found that Cr/CrN/Cr/CrAlN coating has better longitudinal and transverse stress dissipation ability. During the impact of solid particles, high tensile stress is the main reason for the formation and propagation of brittle cracks in the coating. In addition, according to the plastic-brittle (DBT) transition of the Cr layer, it is inferred that the fracture failure mechanism of the coating is a joint mechanism of brittleness and toughness.

Solid particle erosion resistance of Cr-base gradient multilayer coatings

The study aimed to investigate the role of androgen receptor (AR)/cell cycle‐related kinase (CCRK) signalling pathway in chronic hepatitis B virus (HBV) infection and gender differences, and the contribution of AR regulatory factor signal transducer and activator of transcription 3 (STAT3) in it. AR, CCRK, and phosphorylated STAT3 expressions in liver tissues of chronic HBV‐infected patients and non‐HBV controls were determined by western blot and compared between genders. The relationships of expression levels with serum HBV DNA levels, liver inflammation activity, and fibrosis score were analysed in chronic HBV‐infected patients. The relationships between expression levels of three proteins were also analysed. HBV‐infected patients had significantly higher expression levels of AR, CCRK, and p‐STAT3Tyr705 compared with controls (p < .01). The expression levels of AR, CCRK, and p‐STAT3Tyr705 in chronic HBV‐infected patients with severe inflammation were significantly higher than those with mild inflammation (p < .05). Expression levels in patients with heavier fibrosis (stage F4) were higher than in those with less fibrosis (stages F0–3) (p < .01). No gender differences were observed in AR, CCRK, and p‐STAT3Tyr705 levels in non‐HBV controls; higher levels were observed in HBV‐infected males than in HBV‐infected females (p < .05). AR, CCRK, and p‐STAT3Tyr705 levels in liver tissues positively correlated with each other (p < .0001) and with serum HBV DNA levels (p < .0001). In conclusion, in this study, we first found concordant over‐expression of AR, CCRK, and STAT3 in liver tissues of chronic HBV‐infected patients who have not yet developed HCC, significantly correlated with the severity of the disease and showed gender differences. STAT3 may be a potential therapeutic co‐target for chronic HBV infection.

Signal transducer and activator of transcription 3 cooperates with androgen receptor/cell cycle‐related kinase signalling pathway in the progression of hepatitis B virus infection and gender differences

Jing Shi

Papers

Micro-nano multilayer structure design and solid particle erosion resistance performance of CrAlNx/CrAlN coating

Sputtered chromium nitride films with finely tuned intra- and intercolumnar porosities as pseudocapacitive electrode for supercapacitors

Thermal stabilization of nanocrystalline promoting conductive corrosion resistance of TiN–Ag films for metal bipolar plates

Solid particle erosion resistance of Cr-base gradient multilayer coatings

Signal transducer and activator of transcription 3 cooperates with androgen receptor/cell cycle‐related kinase signalling pathway in the progression of hepatitis B virus infection and gender differences