Magnetron sputtered NbN films with electroplated Cr interlayer

NbN films were deposited on SS substrates by reactive DC magnetron sputtering at various N₂ flow rates and substrate biasing. Coatings were studied for their thickness, structure, hardness and adhesion aspects. Process parameters were optimized for deposition of NbN coatings. NbN coatings were then extended on to MS substrates with Cr interlayer in three different thicknesses of 2, 4 and 10 μm. Cr was deposited by electroplating. The duplex coatings have been studied for the improvement with respect to surface hardness by Knoop micro indentation, adhesion by scratch testing and corrosion performance by potentiodynamic polarization technique. Open circuit potentials were also measured.     

Effect of substrate rotation on structure, hardness and adhesion of magnetron sputtered TiB2 coating on high speed steel

Titanium diboride (TiB₂) coatings have been deposited on stationary and rotating high speed steel substrates by magnetron sputtering of a TiB₂ target. The structure and hardness of the coatings and the coating–substrate adhesion have been investigated by X-ray diffraction, field emission scanning electron microscopy, nanoindentation and microscratch tests. The results show that substrate rotation has a significant effect on these structural and properties features. It was found that, with substrate rotation, the TiB₂ coating exhibits a columnar structure with random orientation and relatively low hardness and coating–substrate adhesion. On the other hand, without substrate rotation, the TiB₂ coating shows a strong (001) texture with dense, equiaxed grain structure. The hardness and coating–substrate adhesion of the coatings deposited on stationary substrates are much higher than those deposited on rotating substrates. The observed phenomena are discussed in terms of the energy of the sputtered flux, which varies with the substrate–target distance during deposition.     

Synthesis and characterization of TiBCN coatings deposited by ion beam assisted, co-evaporation electron beam-physical vapor deposition (EB-PVD)

TiC, TiB₂, and super hard TiBCN coatings were successfully deposited by ion beam assisted, electron beam-physical vapor deposition. Titanium, titanium diboride, and carbon (through tungsten) were co-evaporated by energetic electron beams while simultaneously bombarding the substrates with varying ionized gas ratios of nitrogen and argon to obtain super hard TiBCN coatings. The hardness of the TiBCN coating was reported to be equivalent to a soft diamond like carbon film. The adhesion was determined to be greater than 50 N. The hardness, grain size, structure, morphology, crystallographic texture and degree of stress within the coatings were determined using a variety of characterization methods including Vicker's hardness measurements, electron probe microanalysis (EPMA), optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction. The author is not aware of previous TiBCN coatings being deposited by this method.     

Comparison of microstructure and mechanical properties of chromium nitride-based coatings deposited by high power impulse magnetron sputtering and by the combined steered cathodic arc/unbalanced magnetron technique

Sliding, abrasive, and impact wear tests were performed on chromium nitride (CrN)-based coatings deposited on mirror-polished M2 high speed steel substrates by the novel high power impulse magnetron sputtering (HIPIMS) utilising high peak cathode powers densities of 3000 W cm⁻². The coatings were compared to single layer CrN and multilayer superlattice CrN/NbN coatings deposited by the arc bond sputtering (ABS) technique designed to improve the coating substrate adhesion by a combined steered cathodic arc/unbalanced magnetron (UBM) sputtering process. The substrates were metal ion etched using non-reactive HIPIMS or steered cathodic arc at a substrate bias voltage of −1200 V. Subsequently a 2- to 3-μm thick CrN or CrN/NbN coating was deposited by reactive HIPIMS or UBM. No bias was used during the HIPIMS deposition, while the bias during UBM growth was in the range 75-100 V. The ion saturation current measured by a flat electrostatic probe reached values of 50 mA cm⁻² peak for HIPIMS and 1 mA cm⁻² continuous during UBM deposition. The microstructure of the HIPIMS coatings observed by transmission electron microscopy was fully dense in contrast to the voided columnar structure observed in conventional UBM sputtered CrN and CrN/NbN. The sliding wear coefficients of the HIPIMS CrN films of 2.3×10⁻¹⁶ m³ N⁻¹ m⁻¹ were lower by a factor of 4 and the roughness of the wear track was significantly reduced compared to the UBM-deposited CrN. The abrasive wear coefficient of the HIPIMS coating was 2.2×10⁻¹³ m³ N⁻¹ m⁻¹ representing an improvement by a factor of 3 over UBM deposited CrN and a wear resistance comparable to that of the superlattice CrN/NbN. The adhesion of the HIPIMS deposited CrN was comparable to state-of-the-art ABS technology.     

Development of superlattice CrN/NbN coatings for joint replacements deposited by high power impulse magnetron sputtering

The demand for reliable coating on medical implants is ever growing. In this research, enhanced performance of medical implants was achieved by a CrN/NbN coating, utilising nanoscale multilayer/superlattice structure. The advantages of the novel high power impulse magnetron sputtering technology, namely, its unique highly ionised plasma, were exploited to deposit dense and strongly adherent coatings on CoCr implants. Transmission electron microscopy analysis revealed coating superlattice structure with bi-layer thickness of 3.5?nm. CrN/NbN deposited on CoCr samples showed exceptionally high adhesion, critical load values of L_C2?=?50?N in scratch adhesion tests. Nanoindentation tests showed high hardness of 34?GPa and Young’s modulus of 447?GPa. Low coefficient of friction (μ) 0.49 and coating wear coefficient (K _C)?=?4.94?×?10^?16?m³?N^?1?m^?1 were recorded in dry sliding tests. Metal ion release studies showed a reduction in Co, Cr and Mo release at physiological and elevated temperatures (70?°C) to almost undetectable levels (<1?ppb). Rotating beam fatigue testing showed a significant increase in fatigue strength from 349?±?59?MPa (uncoated) to 539?±?59?MPa (coated). In vitro biological testing has been performed in order to assess the safety of the coating in biological environment; cytotoxicity, genotoxicity and sensitisation testing have been performed, all showing no adverse effects.     

Grundlageneigenschaften und Verschleißverhalten von HfB2- und Hf(B,N)-Schichtsystemen

Investigation of Fundamental Properties and Tribological Behaviour of HfB₂ and Hf(B,N) Coatings Thin films of HfB₂ and Hf(B,N), including intermediate layers of pure titanium, were sputtered in a rf sputtering unit on steel substrates. The deposition parameters bias-voltage and deposition pressure in the case of HfB₂ and the nitrogen flow concerning to Hf(B,N) were systematically varied. The characterization of the coatings includes fundamental properties such as thickness, hardness, adhesion and cohesion, structure, morphology, residual stresses and wear resistance of the coatings resulting from the plate on cylinder tribometer. The hardness values, analysed with the Vickers and the indentation depth method (Universal hardness), were extremely high for HfB₂ films, deposited with low deposition pressure or high bias voltage applied on the substrate. These results are probably caused by high residual stresses in the coating. The best wear properties could be obtained by testing the hardest coatings.     

Schäden wälzbeanspruchter DLC‐Schichten auf Stahlsubstraten unterschiedlicher Härte

Damages of slip‐rolling tested DLC coatings on steel substrates of different hardness Extremely hard diamond coatings on hard SSiC substrates, various hard DLC coatings on 100Cr6 substrates (HRC60) as well as selected DLC coatings on unhardened steel substrates (HRC20) were tested under slip‐rolling conditions. Unadditivated paraffin oil was used as a lubricant. The tests were carried out in an Amsler type twin disc tester at initial maximum pressures of P₀=2.3 GPa according to Hertz. The tests were terminated after n=1.000.000 revolutions (endurance tests: n=10.000.000 revolutions) or if a coherent damaged area of A>1 mm² occurred. The slip‐rolling tests showed that the SSiC had a supportive influence on the diamond coatings which, however, failed due to fractures in the substrate. At least two of the DLC coatings on 100Cr6 substrates (HRC60) withstood the slip‐rolling test for up to n=10.000.000 revolutions with nearly no visible damage. These coatings deposited onto a soft, nitrogen alloyed steel (HRC20) were able to adjust to the deformation of the substrate without major damaged areas (A>1 mm²).     

Influence of composition and processing parameters on mechanical properties and erosion response of Ni–TiB2 coatings

Abstract

Sputtered Ni–TiB₂ coatings have been shown to protect Ti–6Al–4V and Inconel 718 substrates from solid particle erosion. However, before new erosion resistant coatings can be efficiently designed, it is essential that the role of mechanical properties in determining erosion resistance be fully understood. In this investigation, nanoindentation techniques were used to quantify the effects of substrate preparation, coating composition, and sputtering process parameters on the elastic moduli and indentation hardness of thin coatings deposited on Ti–6Al–4V and Inconel 718 substrates. The influence of these parameters on coating adhesion was determined using a conventional scratch test. Elastic moduli, indentation hardnesses, and coating adhesion were correlated with erosion behaviour. The erosion resistance of the coatings that exhibited microscopic ductility is dependent on the nodule diameter and coating properties such as hardness, elastic modulus, and fracture toughness.

MST/1697     

Corrosion behavior of nanolayered TiN/NbN multilayer coatings prepared by reactive direct current magnetron sputtering process

TiN, NbN and TiN/NbN multilayer coatings were deposited on tool steel substrates using a reactive DC magnetron sputtering process. The coatings were characterized using X-ray diffraction, nanoindentation, atomic force microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray analysis. The corrosion behavior of TiN/NbN multilayer coatings was studied in 0.5 M HCl and 0.5 M NaCl solutions using potentiodynamic polarization and compared with single layered TiN and NbN coatings. Approximately 1.5 μm thick coatings of TiN, NbN and TiN/NbN multilayers showed good corrosion protection of the tool steel substrate and multilayer coatings performed better than single layered coatings. The corrosion behavior of the multilayers improved with total number of interfaces in the coatings. In order to conclusively demonstrate the positive effect of layering, corrosion behavior of 40-layer TiN/NbN multilayers was studied at lower coating thicknesses (32–200 nm) and compared with single layer TiN coatings of similar thicknesses. The polarization data and SEM studies of these coatings indicated that the corrosion behavior improved with coating thickness and multilayers showed better corrosion resistance as compared to the single layer coatings. Other studies such as intrinsic corrosion, effects of Ti interlayer and post-deposition annealing on the corrosion behavior of the multilayer coatings are also presented in this paper. The results of this study demonstrate that nanolayered multilayers can effectively improve the corrosion behavior of transition metal nitride hard coatings.     

Corrosion behaviour of decorative and wear resistant coatings on steel deposited by reactive magnetron sputtering - Tests and improvements

Depositions of decorative and wear resistant single layer coatings like TiN, Ti(B,N), CrN, NbN, NbON, (Ti,Mg)N and multilayer coatings like Cr/CrN, Nb/NbN, CrN/NbN and NbN/Nb-C:H were performed using reactive magnetron sputtering. The corrosion behaviour of the coated high speed steel substrates was studied in sodium chloride containing media by open-circuit-potential measurements, potentiodynamic corrosion tests and salt spray tests. Up to now, the best improvements with respect to the corrosion resistance in salt spray tests could be obtained for the system (Ti,Mg)N/high speed steel.     

Oxidation study of Cr-Ru hard coatings

Cr-Ru alloy coatings with Cr content ranging from 47 to 83 at.% were deposited at 400 °C by direct current magnetron co-sputtering with a Ti interlayer on silicon substrates. With a total input power of 300 W, the Cr content in the Cr-Ru coatings increased linearly with the increasing input power of Cr. The intermetallic compound phase Cr₂Ru with columnar structure was identified for the as-deposited Cr₅₆Ru₄₄ and Cr₆₅Ru₃₅ coatings, resulting in an increase of hardness up to 15-16 GPa. To evaluate the performance of Cr-Ru coatings as a protective coating on glass molding dies, the annealing treatment was conducted at 600 °C in a 50 ppm O₂-N₂ atmosphere. The outward diffusion and preferential oxidization of Cr in the Cr-Ru coatings resulted in the variations of the crystalline structure, chemical composition distribution, and surface hardness after annealing. X-ray diffraction and transmission electron microscopy (TEM) proved that an oxide scale consisting of Cr₂O₃ formed on the free surface. Scanning electron microscopy and TEM observed the surface morphology and structural variation. The chemical composition depth profiles were analyzed by Auger electron microscopy, verifying the presence of a Cr-depleted zone beneath the oxide scale. The hardness of Cr₅₆Ru₄₄ and Cr₆₅Ru₃₅ coatings decreased to 11-12 GPa after annealing, accompanied by the replacement of the Cr₂Ru phase by the Ru phase.     

Composition and mechanical properties of hard ceramic coating containing α-Al2O3 produced by microarc oxidation on Ti–6Al–4V alloy

Ceramic coatings with 1100–1600 HK_{50 g} hardness were deposited on Ti–6Al–4V alloy substrates using a microarc oxidation (MAO) technique, based on a dielectric barrier discharge created during anodic oxidation in an aqueous electrolyte. The influences of electrolyte concentration, deposition time and the cathodic to anodic current ratio Ic/Ia on phase composition and mechanical properties of the coatings have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis methods (EPMA), as well as microhardness measurement, direct pull-off and impact tests. The results show α-Al₂O₃ phase, which greatly improved the hardness of the coatings, can be obtained at high concentration of NaAlO₂ and its relative content increases with decreasing Ic/Ia ratio. The direct pull-off test and impact test results indicate that the films have the excellent adhesion with the substrate.     

多弧离子镀TiN涂层结合力的影响因素

选择Ｗ６Ｍｏ５Ｃｒ４Ｖ２、３Ｃｒ２Ｗ８Ｖ和ＧＣｒ１５等材料研究了多弧离子镀ＴｉＮ涂层也基体的结合力。结果表明,基体表面粗造度越小、硬度越高,支与基体的结合力越好,涂层厚度以２．５～３．５μｍ为最佳,含Ｖ量高的基体和具有强烈ＴｉＮ（１１１）择优取向的除层结合力好。     

Influence of boron doping on mechanical and tribological properties in multilayer CVD-diamond coating systems

Titanium alloy (Ti6Al4V) substrates were deposited with smooth multilayer coatings, by hot filament chemical vapour deposition technique. The effect of boron doping on lattice parameter, residual stresses, hardness and coefficient of friction in multilayer-diamond coating system was studied. The frictional behaviour of the coatings was studied using a ball-on-disc micro-tribometer by sliding the coated samples of titanium alloy (Ti6Al4V) substrates against alumina (Al₂O₃) balls, and increasing normal load from 1 to 10 N. The average friction coefficient decreased from 0.36 to 0.29 for undoped multilayer-diamond coating system and from 0.33 to 0.18 for boron- doped (BD) multilayer-diamond coating system. The average indentation depths for undoped and BD multilayer- diamond coating systems were found to be equal to ～>58 and ～65 nm, respectively, and their hardness values were 60 and 55 GPa, respectively.     

Investigation of microstructure and mechanical properties of multi-layer Cr/Cr2O3 coatings

Single and multi-layer Cr/Cr₂O₃ coatings were deposited by reactive magnetron sputtering with the total thickness of 7 μm on steel substrates. X-ray diffraction analysis showed that single and multi-layer Cr/Cr₂O₃ coatings have different preferred crystal orientations. Columnar microstructure was detected by transmission electron microscopy both in metal chromium and ceramic chromium oxide layers. Grain size increased with the coating thickness. The value of single and multi-layer coating's fracture toughness is between 4 and 6 MPa·m^1/2 measured with the Berkovich tip indentation, and it is between 2.8 and 3.9 MPa·m^1/2 when measured with the Vickers indenter. The adhesion is about 192.1 and 246.7 J/m² for single and multi-layer coatings, respectively.     

Bias effects on the tribological behavior of cathodic arc evaporated CrTiAlN coatings on AISI 304 stainless steel

In this study, CrTiAlN coatings were deposited on AISI 304 stainless steel by cathodic arc evaporation under a systematic variation of the substrate bias voltage. The coating morphology and properties including surface roughness, adhesion, hardness/elastic modulus (H/E) ratio, and friction behavior were analyzed to evaluate the impact of the substrate bias voltage on the coating microstructure and properties. The results suggest that for an optimized value of the substrate bias voltage, i.e. − 150 V, the CrTiAlN coatings showed increased Cr content and improved properties, such as higher adhesion strength, hardness, and elastic modulus in comparison to the coatings deposited by other substrate bias voltage. Moreover, the optimum coatings achieved a remarkable reduction in the steel friction coefficient from 0.65 to 0.45.     

Formation of superhard Ti-Hf-Si-N/NbN/Al2O3 multilayer coatings for highly effective protection of steel

Hard micro- and nanostructured Ti-Hf-Si-N/NbN/Al₂O₃ multilayer coatings on steel substrates have been obtained for the first time using various deposition technologies and characterized by a combination of methods. It is established that the proposed coatings possess, in addition to high hardness (H = 47–56 GPa), high elastic modulus (E = 435–570 GPa), and good plasticity index (W _e = 0.08–0.11), a rather low friction coefficient that varies within μ = 0.02–0.001 depending on the deposition conditions. The coatings remain stable at temperatures above 1000°C.     

Influence of bi-layer period thickness on the residual stress, mechanical and tribological properties of nanolayered TiAlN/CrN multi-layer coatings

TiAlN/CrN nanoscale multi-layered coatings have been deposited using cathodic arc evaporation system. The coatings were deposited using one Ti₅₀Al₅₀ alloy target and one Cr target with a fixed target power in all the processes, while the bi-layer thickness was varied by various rotation speeds of the substrate holder in order to produce different nanoscale multi-layered period thickness. The texture structure, residual stress, and nanoscale multi-layer period thickness of the coatings were determined by X-ray diffraction using both Bragg-Brentano and glancing angle parallel beam geometries. Hardness and adhesion strength of the coatings were measured by Nano-indentation and Rockwell-C indentation methods, respectively. It has been found that the structural and mechanical properties of the films correlate with nano-scaled bi-layer thickness and crystalline texture. The maximum hardness of nano-scaled TiAlN/CrN multi-layered coatings was approximately 36 GPa with highest residual stress of −6.2 GPa, for a bi-layer thickness ranging from 6 to 12 nm.     

Sputter deposited low-friction and tough Cr-Si3N4 nanocomposite coatings on plasma nitrided M2 steel

Nanocomposite coatings of Cr-Si₃N₄ exhibiting low friction and high toughness were prepared on plasma nitrided AISI M2 steel substrates using an unbalanced magnetron sputtering system. The surface morphology and cross-sectional microstructure of the Cr-Si₃N₄ nanocomposite coatings were studied using field emission scanning electron microscopy (FESEM) techniques. Cr-Si₃N₄ nanocomposite coatings prepared at 48 at.% Cr exhibited a dense microstructure with nanoindentation hardness and toughness values of 18 GPa and 2.0 MPam^½, respectively. Nanoscratch measurements indicated that Cr-Si₃N₄ nanocomposite coatings exhibited good adhesion with a maximum critical load of 150 mN. Ball-on-disc reciprocating tests at a load of 2 N showed that Cr-Si₃N₄ nanocomposite coatings prepared at 48 at.% Cr exhibited an average friction coefficient of 0.30. FESEM studies of the wear tracks indicated that there was no significant wear loss and the Cr-Si₃N₄ nanocomposite coatings exhibited only mild wear due to oxidation.     

Nanoindentation and atomic force microscopy measurements on reactively sputtered TiN coatings

Titanium nitride (TiN) coatings were deposited by d.c. reactive magnetron sputtering process. The films were deposited on silicon (111) substrates at various process conditions, e.g. substrate bias voltage (V_B) and nitrogen partial pressure. Mechanical properties of the coatings were investigated by a nanoindentation technique. Force vs displacement curves generated during loading and unloading of a Berkovich diamond indenter were used to determine the hardness (H) and Young’s modulus (Y) of the films. Detailed investigations on the role of substrate bias and nitrogen partial pressure on the mechanical properties of the coatings are presented in this paper. Considerable improvement in the hardness was observed when negative bias voltage was increased from 100–250 V. Films deposited at |V _B| = 250 V exhibited hardness as high as 3300 kg/mm². This increase in hardness has been attributed to ion bombardment during the deposition. The ion bombardment considerably affects the microstructure of the coatings. Atomic force microscopy (AFM) of the coatings revealed fine-grained morphology for the films prepared at higher substrate bias voltage. The hardness of the coatings was found to increase with a decrease in nitrogen partial pressure.