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Multilayer architectures are effective to tailor the properties of thin films. This study compares the high-temperature structural evolution of (Ti,Al)N and (Ti,Al)N/ZrN by experiments and ab initio calculations. These show that cubic (c-) ZrN layers improve the thermal stability of c-(Ti,Al)N by retarding spinodal decomposition and wurtzite (w-) AlN formation. Correspondingly, (Ti,Al)N and (Ti,Al)N/ZrN exhibit their peak hardness of ∼32.8 and 33.2 GPa upon annealing at 800 and 1000 °C, respectively. Already during growth of c-(Ti,Al)N onto c-ZrN additional Ti-rich c-(Ti,Zr)N interlayers form, but this is not the case when growing c-ZrN onto c-(Ti,Al)N. These different boundaries of c-(Ti,Al)N result in different diffusion activation energies for Al, which is higher at the interface to (Ti,Zr)N than at that to ZrN. Consequently, the interface-directed Al diffusion initiates on the side nearby ZrN, which causes an Al concentration gradient within (Ti,Al)N. This increases the spinodal decomposition period, and thus the critical Al content necessary to trigger w-AlN formation is reached later. Detailed experiments show that at 1000 and 1100 °C also at the c-(Ti,Al)N/ZrN interface, where no c-(Ti,Zr)N developed during growth, a thin c-(Ti,Zr)N layer forms. Only when this layers is completely dissolved into ZrN sublayers at 1200 °C, w-AlN is formed. [Display omitted] • Ab initio and experiments show ZrN layers improve thermal stability of (Ti,Al)N. • The asymmetric boundaries of (Ti,Al)N in (Ti,Al)N/ZrN cause asymmetric diffusion. • Delayed spinodal decomposition of (Ti,Al)N/ZrN is due to long-range Al diffusion. [ABSTRACT FROM AUTHOR]

Metastable (Ti,Al)N thin films with face-centered cubic (fcc) structure are widely applied to protect tools and components used in the machining industry for their high hardness and exceptional thermal stability. Alloying is a simple but powerful strategy to further improve the performance of (Ti,Al)N thin films. Here, the combination of experiments and ab initio calculations allowed us to further improve the mechanical properties, thermal stability, and oxidation resistance of arc-evaporated (Ti,Al)N films through the addition of Nb and Ta. The developed Ti 0.40 Al 0.53 Nb 0.07 N, Ti 0.34 Al 0.52 Nb 0.14 N, Ti 0.40 Al 0.53 Ta 0.07 N, and Ti 0.34 Al 0.50 Ta 0.16 N thin films show a single-phase fcc structure like Ti 0.46 Al 0.54 N. While the hardness (H) of as-deposited (Ti,Al,Nb)N thin films is similar to that of Ti 0.46 Al 0.54 N (30.1 ± 0.4 GPa), it increases to 33.2 ± 0.7 and 34.1 ± 1.1 GPa by alloying with 7 and 16 at.% Ta (metal fraction), respectively. Both alloying elements allow to retard the spinodal decomposition of (Ti,Al)N, as suggested by X-ray diffraction of vacuum-annealed samples. The (Ti,Al)N and (Ti,Al,Nb)N samples exhibit the onset of wurtzite (w-) AlN formation at ~1050 °C, which is postponed to ~1200 °C for the (Ti,Al,Ta)N thin films. Ab initio calculations suggest that age hardening of (Ti,Al)N is improved by Nb and Ta, with Nb being more effective than Ta. This is verified by experiments showing that Ti 0.40 Al 0.53 Nb 0.07 N (Ti 0.34 Al 0.52 Nb 0.14 N) and Ti 0.40 Al 0.53 Ta 0.07 N (Ti 0.34 Al 0.50 Ta 0.16 N) experience an increase of H to 34.7 ± 0.5 GPa (36.7 ± 0.7 GPa) and 35.8 ± 1.0 GPa (37.0 ± 1.1 GPa) when annealed at 1000 °C, compared to the 32.4 ± 0.7 GPa of Ti 0.46 Al 0.54 N annealed at 900 °C. The relative H increase is thus higher for (Ti,Al,Nb)N than for (Ti,Al,Ta)N. Furthermore, Nb and Ta also improve the oxidation resistance of (Ti,Al)N with Ta being more effective than Nb. Based on these results we can conclude that both Nb and Ta elements improve hardness, thermal stability, and oxidation resistance of (Ti,Al)N, with Nb providing more relative hardness gain but Ta providing higher absolute values. • B1-structured (Ti,Al,Nb)N and (Ti,Al,Ta)N thin films with low Nb and Ta contents are synthesized. • Combined experimental and ab initio study reveals age hardening enhancement by Nb and Ta. • (Ti,Al,Nb)N films show larger hardness increment (17– 24 %) than (Ti,Al,Ta)N upon annealing. • (Ti,Al,Ta)N maintains ~32 GPa up to 1200 °C, showing better thermal stability than (Ti,Al,Nb)N. • The oxidation resistance of (Ti,Al)N is improved by Nb and Ta, with Ta being more effective than Nb. [ABSTRACT FROM AUTHOR]

The cubic-wurtzite phase transition of (Ti,Al)N-based thin films at high temperatures is the chief determing factor for their thermal stability. Nevertheless, its mechanism of atomic shear is not yet well explored theoretically. Here, we correlate the coherent interfaces with wurtzite formation within (Ti,Al)N/ZrN multilayers by a combined ab initio and experimental study. Compared to (Ti,Al)N, the multilayer exhibits a delayed formation of hexagonal close-packed (hcp) wurtzite-type AlN phase, which is encapsulated by face-centered cubic (fcc-)(Ti,Zr)N and fcc-(Zr,Ti)N layers when annealed at 1200 °C. Based on the orientation relationships of (200) fcc //(0001) hcp and (220) fcc //(01-10) hcp among hcp-AlN and neighboring fcc-(Ti,Zr)N as well as fcc-(Zr,Ti)N by the solid-state nudged elastic band (SS-NEB) method, two mechanisms for atomic shear during fcc-hcp transition are proposed. The introduction of ZrN layers effectively suppresses the fcc-hcp transition, due to higher activation energies induced by the coherent interfaces. [Display omitted] [ABSTRACT FROM AUTHOR]

The objective of the study was to explore the formation mechanism and thermodynamic properties of chitosan (CS)–potato protein isolate (PPI) complex under DHPM treatment. The transmission electron microscopic (TEM) results showed the formation of a complex between CS and PPI. Meanwhile, particle size and zeta-potential were shown to increase with increasing CS concentration, further confirming the formation of the complex. The surface hydrophobicity results showed CS was bound to PPI by hydrogen bond. The ultraviolet and fluorescence spectral analysis exhibited CS formed a protective mechanism against PPI destruction, preventing the exposure of tyrosine and tryptophan residues. Infrared spectrum and circular dichroism spectral analysis revealed no occurrence of chemical reaction between CS and PPI under DHPM treatment, further indicating that they are bound by hydrogen bond and hydrophobic interaction. Moreover, CS addition was shown to enhance the intermolecular interaction and promote the formation of intermolecular hydrogen bond network. Differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) revealed that CS addition could improve the thermal stability of PPI. These results have shed light on the formation mechanism and thermodynamic properties of the CS/PPI complex and facilitate its application in food industry. [ABSTRACT FROM AUTHOR]

A cesium bismuth germanate, Cs2Bi2O(Ge2O7) (CBGO), was synthesized by a traditional high‐temperature solid‐state reaction. Its structure features a 3D network composed of a 1D chains composed of Bi2O8 dimers that are further bridged by Ge2O7 dimers, forming tunnels of seven member rings (MRs) that are filled by the Cs+ cations. CBGO exhibits extraordinary larger second harmonic generation (SHG) response of about 13.7 times that of KDP (KH2PO4) under 1064 nm laser radiation and 1.1 times that of KTP (KTiOPO4) under 2.05 μm laser radiation, which is the highest among all of the metal germanates reported so far. CBGO possesses a moderate birefringence (0.073 at 1064 nm) and is phase matchable. Furthermore, CBGO melts congruently and exhibits high thermal stability. [ABSTRACT FROM AUTHOR]

Nanoscaled Ti 1-x Si x N/CrAlN multilayers combining the cutting edges of Ti 1-x Si x N and CrAlN coatings are currently the focus of attention of researchers. Here, the structural, mechanical, and thermal properties of Ti 1-x Si x N/CrAlN multilayers with varied Si content were investigated. The hardness values of Ti 1-x Si x N/CrAlN multilayers are individually enhanced to 30.7 ± 1.0 GPa for x = 0, 36.0 ± 1.3 GPa for x = 0.13, and 35.9 ± 1.5 GPa for x = 0.22 from the 27.4 ± 0.3 GPa for CrAlN due to interfacial strengthening effect. Ti 1-x Si x N insertion layers retard the thermal decomposition process of CrAlN. After annealing at 1200 °C, the hardness of Ti 1-x Si x N/CrAlN (x = 0, 0.13, 0.22) multilayers is individually enhanced by ∼6.9, 12.9 and 13.6 GPa from the 18.7 ± 1.1 GPa for Cr 0.32 Al 0.68 N. However, Ti 1-x Si x N insertion layers lead to a drop in the oxidation resistance of CrAlN coatings due to their inferior oxidation resistance. Noticeable is that increasing Si content of Ti 1-x Si x N/CrAlN multilayers causes a decline in the thickness of oxide scales. • The template effect of multilayer increases the solid solubility of Si into TiN. • Ti 1-x Si x N/CrAlN (x = 0, 0.13 and 0.22) multilayers exhibit coherent interface. • The introduction of Ti 1-x Si x N coatings optimizes the thermal stability of CrAlN. • Increasing of Si content improves the oxidation resistance of Ti 1-x Si x N/CrAlN multilayers. [ABSTRACT FROM AUTHOR]

The thermal decomposition of metastable CrAlN coatings into wurtzite AlN and cubic Cr accompanied by N-loss limits their advanced machining applications. Here, the element of Ta is introduced into CrAlN coatings to enhance the mechanical properties and thermal stability. Incorporation of Ta into CrAlN coatings enhances the hardness from 30.8 ± 0.9 GPa for Cr 0.48 Al 0.52 N to 32.7 ± 0.9 GPa for Cr 0.36 Al 0.59 Ta 0.05 N and 34.4 ± 0.7 GPa for Cr 0.31 Al 0.59 Ta 0.10 N. Doping with Ta optimizes the thermal stability of CrAlN coatings by postponing the dissociation of Cr N bonds, where the N-loss process is delayed by ~127–144 °C according to DSC results. Correspondingly, the Ta-containing coatings invariably exhibit higher hardness upon annealing. Nevertheless, the Ta-addition brings about an adverse impact on the oxidation resistance of CrAlN coatings, due to the earlier formation of Ta-containing oxides. After oxidation of 10 h at 1000 °C, the Cr 0.48 Al 0.52 N, Cr 0.36 Al 0.59 Ta 0.05 N and Cr 0.31 Al 0.59 Ta 0.10 N coatings present an oxide layer of ~0.19, 0.27 and 0.30 μm, respectively. • CrAlN and CrAlTaN coatings deposited by cathodic arc evaporation exhibit cubic structure. • CrAlTaN coatings own higher hardness value than CrAlN coating. • CrAlTaN coatings show better thermal stability and higher hardness during annealing. • Ta-addition into CrAlN causes a decreased oxidation resistance due to the formation of Ta-containing oxides. [ABSTRACT FROM AUTHOR]

Alloying is an efficient way to improve or tailor the properties of CrAlN coatings, which have been extensively used as wear protective layers onto cutting and forming tools. Here, we have investigated the influence of Nb on the mechanical properties, thermal stability and oxidation resistance of CrAlN coatings. Cr 0.48 Al 0.52 N, Cr 0.38 Al 0.57 Nb 0.05 N, and Cr 0.35 Al 0.55 Nb 0.10 N coatings, deposited by cathodic arc evaporation, reveal a single-phase face-centered cubic structure with a hardness of 30.8 ± 0.9, 32.3 ± 0.8 and 32.3 ± 1.0 GPa, respectively. The addition of Nb improves the thermal stability of CrAlN via postponing the dissociation of Cr N bonds from 1100 °C for CrAlN to 1200 °C for CrAlNbN, which endows Nb-containing coatings with the higher hardness upon annealed at elevated temperatures. Nevertheless, alloying with Nb decreases the proportion of protective (Cr, Al) 2 O 3 layer and promotes the early formation of CrNbO 4 and thus weakens the oxidation resistance of CrAlN coating. After oxidation at 1000 °C with a duration of 10 h, the Cr 0.38 Al 0.57 Nb 0.05 N and Cr 0.35 Al 0.55 Nb 0.10 N coatings exhibit a thicker oxide scale of ~0.7 and ~0.8 μm with Cr-rich/(Al, Nb)-rich bilayered structure, while the Cr 0.48 Al 0.52 N still have a dense oxide layer with a thickness of ~0.2 μm. [ABSTRACT FROM AUTHOR]

Since the superiority of tribological properties, V-containing coatings, with the potential to generate lubricious Magnéli oxides at elevated temperatures, are regarded as excellent candidates for machining applications. Here, a study was conducted to shed light on the intrinsic thermal stability, mechanical properties and oxidation resistance of V-alloyed CrAlN coatings deposited by cathode arc evaporation. The hardness of Cr 0.48 Al 0.52 N and Cr 0.44 Al 0.50 V 0.06 N coatings with a single-phase face-centered cubic structure is 30.8 ± 0.9 and 33.0 ± 1.3 GPa, respectively. Upon annealing in Ar atmosphere, Cr 0.44 Al 0.50 V 0.06 N coating reveals a retarded precipitation of wurtzite AlN as well as a postponement in Cr–N disintegration as compared to V-free Cr 0.48 Al 0.52 N coating, owing to the solid solution of V with a stronger binding capacity with nitrogen. The improved structural stability of Cr 0.44 Al 0.50 V 0.06 N coating contributes to the mild decline in hardness and elastic modulus upon annealing. When exposed to air, the incorporation of V into CrAlN promotes the formation of (Al, Cr) 2 O 3 mixed oxide as well as additional V 2 O 5 , leading to a significantly lower onset temperature for oxidation. The existence of V 2 O 5 degrades the protective of (Al, Cr) 2 O 3 oxide layer and causes a complete oxidation of Cr 0.44 Al 0.50 V 0.06 N coating at 950 °C, where only a dense and thin oxide scale can be detected in Cr 0.48 Al 0.52 N coating. [ABSTRACT FROM AUTHOR]

In recent years, TiAlON coatings have attracted broad attention in the machining field for their excellent toughness and machining performance. Here, we explore the microstructure, mechanical properties and thermal stability of Ti-Al-O-N coatings with the O/(O + N) ratio from 0 to 1. Combined experiments and first-principle calculations show that metal vacancies induced by charge balancing is the main incentive for increased non-metal/metal ratio and decreased lattice constant with increasing O concentration. Ti 0.42 Al 0.58 N 0.95 , Ti 0.41 Al 0.59 (O 0.08 N 0.92) 1.02 and Ti 0.41 Al 0.59 (O 0.18 N 0.82) 1.13 coatings reveal a single-phase face-centered cubic (fcc) structure and almost constant hardness of ∼32 GPa. Further increasing oxygen content leads to the formation of amorphous oxides. Attributed to the negative effect of metal vacancies, weaker metal‑oxygen bond and amorphous oxides, the hardness values of Ti 0.42 Al 0.58 (O 0.57 N 0.43) 1.25 , Ti 0.40 Al 0.60 (O 0.79 N 0.21) 1.39 and Ti 0.41 Al 0.59 O 1.52 are reduced to 27.7 ± 1.1, 22.5 ± 0.6 and 10.6 ± 0.7 GPa, respectively. All coatings present the age-hardening ability during annealing, where the temperatures of hardness peak for the O-containing nitride coatings are higher than that for Ti 0.42 Al 0.58 N 0.95. This beneficial effect on the thermal stability can be attributed to the retarded wurtzite AlN formation and the precipitation strengthening of Al-containing oxides. However, for N-free Ti 0.41 Al 0.59 O 1.52 coatings, the transformation of anatase-rutile TiO 2 conduces to inferior thermal stability. [Display omitted] • Addition of O into TiAlN induces metal vacancies by charge balancing. • The transition from cubic to cubic and amorphous oxide phase occurs with increasing O-content. • The mechanical properties of TiAlON coatings scale with the O-content. • Incorporation of O has a beneficial effect on the thermal stability of TiAlN. [ABSTRACT FROM AUTHOR]

Recently, the favorable impact of O-addition on the oxidation resistance, toughness and machining performance of Ti 1-x Al x N coatings has attracted a wide range of research interests. We systematically studied the effect of O-addition on structure, mechanical and thermal properties of Ti 1-x Al x N coatings by experimental and theoretical methods. The hardness values of Ti 0.42 Al 0.58 N 0.95 , Ti 0.41 Al 0.59 (O 0.08 N 0.92) 1.02 , Ti 0.41 Al 0.59 (O 0.12 N 0.88) 1.06 and Ti 0.41 Al 0.59 (O 0.18 N 0.82) 1.13 with face-centered cubic (c) structure are 31.8 ± 0.7, 31.9 ± 0.6, 32.1 ± 0.8 and 31.7 ± 0.8 GPa, respectively. Thus, incorporation of oxygen into Ti 1-x Al x N has no impact on the hardness (within the investigated range) of the films in their as-deposited state. After annealing, the peak hardness increases with the oxygen content and is 34.3 ± 0.7 GPa with 900 °C, 35.1 ± 0.8 GPa with 1100 °C and 35.9 ± 0.5 GPa with 1100 °C for Ti 0.42 Al 0.58 N 0.95 , Ti 0.41 Al 0.59 (O 0.08 N 0.92) 1.02 and Ti 0.41 Al 0.59 (O 0.12 N 0.88) 1.06 , respectively. First-principles calculations combing the climbing image nudged elastic band (CI-NEB) method reveal that the incorporated oxygen retards the thermal decomposition by increasing the diffusion activation energy for Al diffusion. First-principles calculations further show that the most preferred decomposition products of c-Ti 1-x Al x (O y N 1-y) z are c-TiO y N 1-y and c-AlN. Moreover, although the highest oxygen-containing film, Ti 0.41 Al 0.59 (O 0.18 N 0.82) 1.13 , contained a noticeable quantity of wurtzite (w-)AlN when annealed at 1200 °C, the sample exhibits the peak hardness of 35.5 ± 0.8 GPa. This, we attribute to the strengthening effect due to the precipitation of nano-sized α-Al 2 O 3 and θ-Al 2 O 3. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, boron was introduced into TiAlN coating to improve its performance. Ti 0.44 Al 0.56 N, Ti 0.42 Al 0.54 B 0.04 N, and Ti 0.36 Al 0.55 B 0.09 N coatings were synthesized by arc evaporation, and the effect of B on structure, mechanical and thermal properties of TiAlN coatings were investigated by detailed experiments. Furthermore, we studied the formation energy (E f) of cubic and wurtzite phases in Ti 1-x-y Al x B y N coatings by density functional theory (DFT) calculations. First-principle calculations indicate that the incorporation of B reduces the solid solubility of Al in cubic TiN, which is confirmed by the experimental results. Ti 0.44 Al 0.56 N coatings show a face-centered cubic structure while Ti 0.42 Al 0.54 B 0.04 N and Ti 0.36 Al 0.55 B 0.09 N exhibit a mixed structure of cubic and wurtzite phases. In addition, experimental results show that doping B by 4 at.% gives rise to an increase in hardness from 30.1 ± 0.4 GPa of Ti 0.44 Al 0.56 N to 32.7 ± 0.9 GPa of Ti 0.42 Al 0.54 B 0.04 N, while further increasing B content to 9 at.% triggers a dramatic decrease of the hardness down to 23.0 ± 0.6 GPa (Ti 0.36 Al 0.55 B 0.09 N). Alloying with B also significantly improves the oxidation resistance of TiAlN coatings by retarding the transformation of a-TiO 2 to r-TiO 2 and promoting α-Al 2 O 3 formation. • Ab initio calculations show that B-addition reduces the solubility of Al in c-TiN. • B-addition into TiAlN promotes the wurtzite AlN formation during deposition. • Adding 4 at.% B into TiAlN coating increases its hardness. • Alloying with B improves the oxidation resistance of TiAlN coatings. [ABSTRACT FROM AUTHOR]

CrAlN coatings are recognized as outstanding protective layers for machining tools owing to their high hardness and exceptional oxidation resistance. However, the thermal stability of CrAlN coatings is relatively inferior. For tailoring the thermal properties of CrAlN coatings and enabling them to serve for severe working conditions, the element of B was introduced into CrAlN coatings in this study. Cr 0.42 Al 0.58 N, Cr 0.39 Al 0.58 B 0.03 N and Cr 0.35 Al 0.59 B 0.06 N coatings were deposited by cathodic arc evaporation, and the influence of B-incorporation on the structure, mechanical and thermal properties of CrAlN coatings were studied in detail. X-ray diffraction determinations manifest that the three coatings reveal a face-centered cubic structure. The hardness of Cr 0.48 Al 0.52 N is increased from 30.2 ± 0.7 GPa to 35.0 ± 1.3 GPa (Cr 0.39 Al 0.58 B 0.03 N) and 36.4 ± 1.2 GPa (Cr 0.35 Al 0.59 B 0.06 N), respectively, due to solid solution strengthening and grain refinement. Adding B into CrAlN coatings postpones the formation of wurtzite (w-) AlN and hexagonal (h-) Cr 2 N, thus improving their thermal stability. Additionally, the oxidation resistance of CrAlN coatings is further optimized by B-addition owing to the promoted formation of alpha (α-) Cr 2 O 3. The isothermal oxidation experiment at 1100 °C for 15 h reveals that the oxide thicknesses of Cr 0.39 Al 0.58 B 0.03 N and Cr 0.35 Al 0.59 B 0.06 N coatings are decreased to ~1.6 and 1.8 μm, compared with the ~2.7 μm of Cr 0.42 Al 0.58 N coating. • CrAlN and CrAlBN coatings all reveal face-centered cubic structure • CrAlBN coatings show higher hardness values than CrAlN • CrAlBN coatings exhibit enhanced thermal stability compared with CrAlN • The oxidation resistance of CrAlN coating is optimized by B-addition [ABSTRACT FROM AUTHOR]

In this study, TiN coatings with favorable phase stability were introduced to CrAlNbN coatings for stabilizing the structure of CrAlNbN coatings during annealing. The structure, mechanical properties and thermal stability of CrAlNbN/TiN multilayers and the monolithic counterparts were comparatively studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and nanoindentation. All coatings exhibit face-centered cubic structure, and CrAlNbN/TiN multilayer with smaller bilayer period reveals superlattice structure. T he coherent growth of CrAlNbN sublayers along with TiN template layers, and the relatively higher binding energy of Ti–N bonds than Cr–N retards the thermal decomposition procedure of CrAlNbN/TiN multilayers, where the initiation temperatures of w-AlN precipitation and N-loss are elevated by 100 and 200 °C, respectively. The architecture of CrAlNbN/TiN multilayers effectively improves the capability of corresponding monolithic layers to maintain hardness upon thermal load, which is beneficial for their high-temperature applications. • CrAlNbN/TiN multilayers reveal coherent interface. • CrAlNbN/TiN multilayers reveal higher hardness than calculated values by mixing rule. • The TiN insertion layer retards the thermal decomposition process of CrAlNbN. • CrAlNbN/TiN multilayers show milder declining trend of hardness during annealing. [ABSTRACT FROM AUTHOR]

In order to optimize the overall properties of CrAlN coating, TiAlSiN insertion layers with exceptional thermal stability are introduced into CrAlN coating. Based on the template effect of CrAlN layer, the Ti 0.53 Al 0.38 Si 0.09 N layer can be stabilized in a metastable cubic structure, and thus exhibits a high hardness of 33.8 ± 0.7 GPa, whereas the Ti 0.48 Al 0.38 Si 0.14 N layer still crystallizes in the mixed cubic and wurtzite structure, and shows a low hardness of 28.9 ± 0.9 GPa. TiAlSiN insertion layers improve the thermal stability of CrAlN coating by suppressing the breakage of Cr–N bonds. Additionally, TiAlSiN/CrAlN multilayers reveal an age-hardening ability and also higher hardness than Cr 0.32 Al 0.68 N coating during annealing up to 1200 °C. Compared with Cr 0.32 Al 0.68 N coating, TiAlSiN/CrAlN multilayers show inferior oxidation resistance below 1000 °C, but better antioxidative performance at higher temperatures. Furthermore, Ti 0.48 Al 0.38 Si 0.14 N/CrAlN exhibit better oxidation resistance than Ti 0.53 Al 0.38 Si 0.09 N/CrAlN due to the elevated Si content. On the whole, Ti 0.53 Al 0.38 Si 0.09 N/CrAlN multilayer reveals the best comprehensive properties. • Ti 0.53 Al 0.38 Si 0.09 N/CrAlN multilayer exhibits the highest hardness of ∼33.8 GPa. • The introduction of TiAlSiN optimizes the thermal stability of CrAlN. • TiAlSiN improves the high-temperature oxidation resistance of CrAlN above 1000 °C. • Increasing Si content improves the oxidation resistance of TiAlSiN/CrAlN. [ABSTRACT FROM AUTHOR]

In this work, the effect of B and Si addition on the microstructure, mechanical properties, thermal stability and oxidation resistance of CrAlN coating was studied. Cr 0.42 Al 0.58 N, Cr 0.37 Al 0.59 B 0.02 Si 0.02 N, and Cr 0.35 Al 0.58 B 0.03 Si 0.04 N coatings were prepared by cathode arc evaporation. The three coatings all reveal single-phase cubic structure. The hardness of Cr 0.37 Al 0.59 B 0.02 Si 0.02 N coating increases to 32.5 ± 1.1 GPa compared with Cr 0.42 Al 0.58 N (30.2 ± 0.7 GPa) due to solid solution strengthening. However, the thickened grain boundary due to the segregation of excess B and Si in Cr 0.35 Al 0.58 B 0.03 Si 0.04 N slightly reduces the hardness to 31.6 ± 0.7 GPa. The addition of B and Si by 2 at.% retards the precipitation of w-AlN and the dissociation of Cr N bonds of CrAlN coating upon annealing. However, the increase of B and Si contents makes no difference to the formation temperature of h-Cr 2 N, but promotes the formation of w-AlN during annealing. The addition B and Si endows both CrAlBSiN coatings with higher hardness after annealing in comparison with Cr 0.42 Al 0.58 N. After oxidation at 1100 °C for 15 h, Cr 0.42 Al 0.58 N, Cr 0.37 Al 0.59 B 0.02 Si 0.02 N, and Cr 0.35 Al 0.58 B 0.03 Si 0.04 N coatings show oxide layers with thicknesses of ∼2.8, ∼1.0 and ∼1.2 μm, respectively. Among the three coatings, Cr 0.37 Al 0.59 B 0.02 Si 0.02 N coating reveals the best overall performance. • The addition of B and Si improves the oxidation resistance of CrAlN. • The decomposition of CrAlN coating is retarded by the addition of B and Si. • CrAlBSiN show higher hardness than CrAlN in as-deposited and annealed states. • Cr 0.37 Al 0.59 B 0.02 Si 0.02 N coating reveals the best overall performance. [ABSTRACT FROM AUTHOR]

Recently, the development of AlN-based multilayers has raised interest due to the probability of improved performance from both Al-addition and multilayer architecture. Here we prepared AlN/Cr 1- x Al x N (x = 0.44 and 0.64) multilayers, with monolithic AlN and Cr 1- x Al x N coatings as reference. The dependence of microstructure, mechanical properties, thermal stability, oxidation and corrosion resistance on Al content of CrAlN layers were investigated in detail. The AlN/Cr 0.56 Al 0.44 N (low-Al ML) shows a superlattice feature with single-phase face-centered cubic (fcc) structure and its hardness is 29.7 ± 1.0 GPa, which is ∼4.8 GPa higher than the theoretical value from rule of mixture. While the increase of Al content in CrAlN layer leads to a mixed cubic and wurtzite structure of AlN/Cr 0.36 Al 0.64 N (high-Al ML) with semi-coherent interface. Accordingly, the high-Al ML only has a hardness of 16.9 ± 0.4 GPa. During annealing, AlN/Cr 1- x Al x N multilayers reveal hindered decomposition of Cr N bonds, compared with the corresponding Cr 1- x Al x N monoliths. The low-Al ML possesses the best thermal stability, reflected by its high hardness maintained up to 1000 °C, which is 100 °C higher than Cr 1- x Al x N monoliths. Additionally, AlN/Cr 1- x Al x N multilayers show improved oxidation resistance, with high-Al content in CrAlN layers favorable for such resistance. After oxidation at 1100 °C for 15 h, the low-Al ML and high-Al ML generate oxide scales with thicknesses of ∼1.6 and ∼1.4 μm, respectively, compared to the fully oxidized Cr 0.56 Al 0.44 N and ∼1.8-μm-thick oxide scale of Cr 0.36 Al 0.64 N. In electrochemical experiments, the corrosion current density (I corr) of multilayer coatings decreases, compared to their corresponding monolithic coatings. • Cubic CrAlN sublayers stabilize the cubic growth of wurtzite AlN sublayers. • Increasing Al content induces interfacial transition from coherent to semi-coherent. • Construction of multilayer structure enhances the thermal stability of coating. • The oxidation resistance of multilayer coating is dominated by the Al content. [ABSTRACT FROM AUTHOR]

Recently, TiAlSiN thin films have attracted increasing research interest due to their potential to have simultaneously enhanced hardness, thermal stability, and oxidation resistance compared with Si-free TiAlN films. Previous studies have revealed that a relatively low Si content (2.1–6.0 at.% Si) is essential for the phase stability and hardness of TiAlSiN thin films. Despite the optimum Si content for the hardness of TiAlSiN thin films being proposed, a systematical study concerning the optimum Si content for tailored phase stability, thermal stability, and oxidation resistance of TiAlSiN thin films is still missing. Here, we arc-deposited Ti 1-x-z Al x Si z N thin films (x = ~0.45, 0.01 ≤ z ≤ 0.08), and investigated the dependence of their structure, mechanical properties, thermal stability, and oxidation resistance on Si content. XRD analysis reveals the transformation from single-phase cubic structure for z ≤ 0.06 to a cubic-wurtzite dual-phase structure for z = 0.08. Increasing the Si content of cubic-structured Ti 1-x-z Al x Si z N thin films conduces a continuous increase of hardness (H) from 29.3 ± 0.5 GPa for z = 0.01 up to 37.3 ± 0.7 GPa for z = 0.06, whereas the w-AlN formation leads to a drop of H to 32.8 ± 0.6 GPa for z = 0.08. Furthermore, enhancing the Si content from z = 0.01 to z = 0.06 continuously improves film thermal stability, where the Ti 0.48 Al 0.46 Si 0.06 N film presents the highest hardness values within the whole studied temperature range (as-deposited, 800–1200 °C). All Ti 1-x-z Al x Si z N films undergo age-hardening, with peak H of 33.3 ± 1.0 GPa at 1000 °C for z = 0.01, 35.0 ± 0.6 GPa at 1100 °C for z = 0.02, 35.4 ± 0.5 GPa at 1100 °C for z = 0.03, 40.2 ± 0.7 GPa at 1200 °C for z = 0.06, and 37.8 ± 0.6 GPa at 1100 °C for z = 0.08. Additionally, the oxidation resistance of Ti 1-x-z Al x Si z N films at 800–1000 °C is improved with increasing Si content, due to the suppressed transformation of anatase-to-rutile TiO 2 and the promoted formation of a top dense oxide scale. After oxidation at 900 °C for 15 h, the Ti 0.54 Al 0.45 Si 0.01 N film has been completely oxidized, whereas Ti 0.53 Al 0.45 Si 0.02 N, Ti 0.51 Al 0.46 Si 0.03 N, Ti 0.48 Al 0.46 Si 0.06 N and Ti 0.45 Al 0.47 Si 0.08 N films exhibit oxide scales of ~1.7, ~1.4, ~1.2 and ~0.9 μm, respectively. Overall, we propose z = 0.06 as the optimum Si content for the over-rounded performance of Ti 1-x-z Al x Si z N thin films. • TiAlSiN films with close Al content and gradient Si content were deposited by arc evaporation. • Elevated Si content of cubic TiAlSiN films favors the hardness and thermal stability. • Enhancing Si content improves the oxidation resistance of TiAlSiN films. • 6 at.% at metal sublattice is the optimum Si content for the overall performance of TiAlSiN films. [ABSTRACT FROM AUTHOR]

In this study, TiAlTaN/TiAlSiN multilayer is developed to combine the outstanding oxidation resistance of Ti 0.34 Al 0.48 Ta 0.18 N and prominent hardness and thermal stability of Ti 0.56 Al 0.3 4 Si 0.10 N coatings. The microstructure, mechanical and thermal properties of TiAlTaN/TiAlSiN multilayer and corresponding monolithic coatings were investigated. The hardness of Ti 0.34 Al 0.48 Ta 0.18 N, Ti 0.56 Al 0.3 4 Si 0.10 N monolithic and TiAlTaN/TiAlSiN multilayered coatings with face-centered cubic structure are 32.4 ± 0.9, 36.5 ± 0.9 and 36.7 ± 0.8 GPa, respectively. All coatings reveal age-hardening with the peak hardness values of 35.0 ± 0.6, 39.2 ± 0.7 and 39.5 ± 0.9 GPa, corresponding to the annealing temperatures of 900, 1000 and 900 °C, respectively. Furthermore, TiAlTaN/TiAlSiN multilayer proclaims the best oxidation resistance among the three coatings. After oxidation at 1000 °C for 10 h, Ti 0.34 Al 0.48 Ta 0.18 N and TiAlTaN/TiAlSiN reveal oxide layers of ~1.1 μm and ~0.4 μm, respectively, while Ti 0.56 Al 0.3 4 Si 0.10 N coating has been completely oxidized. • TiAlTaN/TiAlSiN multilayer deposited exhibits coherent interface. • The multilayer shows comparable hardness with TiAlSiN coating. • TiAlTaN/TiAlSiN multilayer reveals a pronounced age-hardening ability. • The multilayer shows better oxidation resistance than the monolayers. [ABSTRACT FROM AUTHOR]

• TiSiN/TiAlN multilayers exhibit the epitaxial growth with coherent interfaces. • TiSiN/TiAlN multilayers release effectively the stress of TiSiN coatings. • TiSiN/TiAlN exhibit a wide temperature range of age-hardening up to 1200 °C. • TiSiN/TiAlN multilayers reveal better oxidation resistance. ga1 Multilayer architecture to optimize the properties of TiAlN coating attracts extensive interests in industrial applications. Here, the structure, mechanical and thermal properties of Ti 1−x Si x N/TiAlN (x = 0.13, 0.17 and 0.22) multilayers consisting of ~6.0 nm Ti 1−x Si x N and ~4.0 nm TiAlN sublayers as well as TiAlN monolithic coating are investigated. Ti 1−x Si x N/TiAlN multilayers with an epitaxial growth between Ti 1−x Si x N and TiAlN sublayers exhibit a similar hardness value of ~37.6 GPa, corresponding to ~30.9 GPa of TiAlN. Annealing of TiAlN coating induces an age-hardening related to spinodal decomposition, and thus conduces to a peak hardness of ~32.8 GPa at 800 °C. The coherent strain between Ti 1−x Si x N and TiAlN sublayers of Ti 1−x Si x N/TiAlN multilayers retards the thermal decomposition of TiAlN and thus broadens the temperature range of age-hardening. Therefore, the hardness of Ti 1−x Si x N/TiAlN multilayers still stay 41.1 ± 1.4 GPa even after annealing at 1200 °C, which corresponds to a low hardness of ~22.1 GPa of TiAlN coating. Furthermore, after oxidation of 10 h at 850 °C, Ti 1−x Si x N/TiAlN multilayers exhibit oxide scales of ~2.65 µm for x = 0.13, ~2.1 µm for x = 0.17 and ~1.9 µm for x = 0.22, respectively, whereas TiAlN and Ti 1−x Si x N coatings have been completely oxidized. [ABSTRACT FROM AUTHOR]

In this study, the effect of oxygen addition on the structure, mechanical and thermal properties of CrN coatings was investigated. CrN, Cr 0.50 O 0.07 N 0.43 and Cr 0.47 O 0.22 N 0.31 coatings reveal a single-phase cubic structure, and further increasing oxygen content results in the formation of a corundum structured Cr 2 O 3 coating. An increased hardness from ~16.9 GPa for CrN to ~21.9 GPa for Cr 0.50 O 0.07 N 0.43 , ~27.0 GPa for Cr 0.47 O 0.22 N 0.31 , and finally ~28.6 GPa for α-Cr 2 O 3 is obtained. Cr 0.50 O 0.07 N 0.43 and Cr 0.47 O 0.22 N 0.31 coatings show a deferred onset temperature of nitrogen loss than CrN by ~100 °C. During annealing, the hardness value of the CrN coating decreases to ~11.3 GPa at 900 °C and then inversely increases to ~17.9 GPa at 1200 °C, while those of Cr 0.50 O 0.07 N 0.43 and Cr 0.47 O 0.22 N 0.31 coatings exhibit a continuous drop to ~14.5 and ~20.6 GPa at 1200 °C, respectively. The oxidation resistance of Cr-O-N coating is closely related to oxygen content. After oxidation at 800 °C for 20 h, the oxide scales of CrN, Cr 0.50 O 0.07 N 0.43 and Cr 0.47 O 0.22 N 0.31 coatings are ~0.22, ~0.16 and ~0.55 μm in thickness, respectively. In addition, the Cr 2 O 3 coating always retains excellent mechanical and thermal properties regardless of in Ar or synthetic air. • O-addition into CrN causes a structural transformation from cubic to hexagonal. • The O-containing coatings reveal higher hardness than CrN coating. • Doping with O into CrN postpones the onset temperature of N-loss by ~100 °C. • The oxidation resistance of Cr-O-N coating is closely related to the O content. [ABSTRACT FROM AUTHOR]