Coating Deposition Temperature Research Articles

Structure, mechanical, and sand erosion behavior of TiN/Ti coating deposited at various temperature

In this paper, the microstructure evolution, mechanical properties, sand erosion performance, and failure mechanism of multilayer TiN/Ti coatings deposited at different substrate temperatures (25 °C, 100 °C, 300 °C, and 500 °C) were investigated. TEM results showed the average columnar grain width of the TiN layer at the four deposited temperatures was 18.4 nm, 30.7 nm, 58.9 nm, and 86.9 nm, respectively. Additionally, a transition from columnar to equiaxed grain morphology was observed in the Ti layer when the deposition temperature was raised to 500 °C. The hardness of TiN/Ti coating decreased from 26 GPa at 25 °C to 22 GPa at 100 °C, 300 °C and 500 °C, which might be attributed to the decreased residual stress with the increase of the deposition temperature. The adhesion force of the deposited coating on the substrate increased firstly, peaked 72 N at 300 °C and then decreased. Sand erosion tests indicated that the sand erosion rate of the TiN/Ti coating initially decreased then rebound as the coating deposition temperature increased. The TiN/Ti coating deposited at 300 °C exhibited the optimal anti-erosion performance. Under a 45° sand erosion incident angle, the top TiN layer cracked and propagated parallelly to the incident angle and intersected, resulting in coating delamination. Under a 90°incident angle, the crack in the soft Ti layer intersected with the annular crack formed in the brittle TiN layer, leading to the removal of the coating.

Realization of ultra-low friction coefficient in thin-film solid lubricant coatings containing nano-sized layers of molybdenum and tantalum disulfides

Solid lubricating coatings consisting of alternating layers of molybdenum and tungsten disulfide were obtained by the method of reactive pulsed laser deposition. The layers were deposited at temperatures of 400 and 500 °C, which caused the formation of a layered packing of atoms characteristic of the hexagonal 2H-phase. The layer thickness was about 10 nm, and the basal planes of the layered atomic packing were oriented predominantly parallel to the substrate surface over the entire thickness of the layers. The study of tribological properties was carried out by the method of sliding a ball over a disk in a nitrogen atmosphere with varying the load on the counter body from 5 to 9 N. The value of the friction coefficient depended on the load on the counter body. The lowest value of the coefficient of friction was 0.01, and it was found under the highest load for coatings obtained at 500 °C. A decrease in the coating deposition temperature had a negative effect on the antifriction properties of the coating.

Glass Coating Deposition Temperature on the Inner Surface of Heat-Exchange Tube

The deposition temperature of a glass coating on the inner surface of a heat-exchanger tube was studied. The choice of coating deposition temperature depends on the physico-mechanical properties, geometric dimensions, and temperature distribution at any point of the coating and the metallic part of the heat-exchange tube. The variation of the deposition temperature field of glass coatings on the inner surface of a tube as a function of the heating time of the electric-heating furnace is determined theoretically. It is found that during deposition of a glass coating on the inner surface of the tube the temperature largely depends on the brand and thickness of the sealed glass rod.

Application of TiN/TiO2 coatings on stainless steel: composition and mechanical reliability

The paper reports on the effect of the substrate temperature (350 °C, 380 °C and 420 °C) during reactive magnetron sputtering of a TiN film on the phase composition, texture and mechanical properties of TiN/TiO2 coatings on 304L stainless steel substrates. Pure Ti was used as a cathode source of Ti. The texture and unit cell parameters of both TiN and TiO2 phases of the coating are discussed in relation with the tribological properties and adhesion of the coating. The scratch tests performed showed that the nitride deposited at 380 °C, having the highest unit cell parameter and a predominant (111) texture, possessed the lowest friction coefficient (μ), tangential force and brittleness. The anatase-type TiO2 with predominant (101) pole density and increased c unit cell parameter showed the highest stability on the nitride deposited at 420 °C. The results indicated that the friction coefficient, tangential force and critical forces of fracture could be varied by controlling the coating deposition temperature.

Effect of substrate temperature and nitrogen concentration during sputtering on corrosion behaviour of AlN coatings

Aluminium nitride coatings were formed on stainless steel substrate by DC-reactive balanced magnetron sputtering at various nitrogen concentrations in the sputtering gas mixture, and different substrate temperatures. The electrochemical corrosion behaviour of the coatings obtained was studied in 0.5 M H2SO4. Continuous improvement in corrosion resistance of the coatings was observed with increasing coating deposition temperature up to 500 °C. The corrosion potential shifted from −0.66 VSCE at 100 °C to −0.33 VSCE at 500 °C. Accordingly, the corrosion current density decreased significantly with increase in the deposition temperature. However, no major difference in corrosion behaviour could be noticed for the coatings formed at various nitrogen concentrations.

Characterization of Thin Film Dissolution in Water with in Situ Monitoring of Film Thickness Using Reflectometry.

Reflectometry was implemented as an in situ thickness measurement technique for rapid characterization of the dissolution dynamics of thin film protective barriers in elevated water temperatures above 100 °C. Using this technique, multiple types of coatings were simultaneously evaluated in days rather than years. This technique enabled the uninterrupted characterization of dissolution rates for different coating deposition temperatures, postdeposition annealing conditions, and locations on the coating surfaces. Atomic layer deposition (ALD) SiO2 and wet thermally grown SiO2 (wtg-SiO2) thin films were demonstrated to be dissolution-predictable barriers for the protection of metals such as copper. A ∼49% reduction in dissolution rate was achieved for ALD SiO2 films by increasing the deposition temperatures from 150 to 300 °C. ALD SiO2 deposited at 300 °C and followed by annealing in an inert N2 environment at 1065 °C resulted in a further ∼51% reduction in dissolution rate compared with the nonannealed sample. ALD SiO2 dissolution rates were thus lowered to values of wtg-SiO2 in water by the combination of increasing the deposition temperature and postdeposition annealing. Thin metal films, such as copper, without a SiO2 barrier corroded at an expected ∼1-2 nm/day rate when immersed in room temperature water. This measurement technique can be applied to any optically transparent coating.

Improved corrosion protection of magnesium by hydrothermally deposited biodegradable calcium phosphate coating

The corrosion protection of hydrothermally deposited calcium phosphate coatings on AZ31 magnesium alloy were studied for their potential use in biocompatible and bioresorbable temporary implants. The coatings mainly consisted of calcium phosphate phases (monetite and tricalcium phosphate). Potentiodynamic and electrochemical impedance spectroscopy (EIS) confirmed that the coatings provided varying levels of corrosion protection depending on the coating deposition temperature and duration. EIS results showed that the size of capacitance loops and the absolute impedance value (|Z|) increases by increasing the deposition temperature and corresponding growth in coating thickness. In agreement with the electrochemical experiments, immersion tests in simulated body fluid also indicated large improvement in corrosion protection as the mass loss was significantly reduced when coating was applied as compared to the bare metal. Using the thickest coating obtained at 190 °C deposition temperature, the corrosion current density of the coated magnesium was 10,000 fold lower compared to the bare metal. This result confirmed that the new hydrothermal coating is suitable to protect Mg implant against corrosion with further advantage of being bioactive and biodegradable.

Control the Corrosion of Magnesium for Implant Application By Hydrothermally Deposited Biodegradable Calcium Phosphate Coating

The corrosion protection of hydrothermally deposited calcium phosphate coatings on AZ31 magnesium alloy was studied in simulated body fluid (SBF) solution for their potential use as biodegradable implants. The coating mainly consisted of bioresorbable monetite phases. Potentiodynamic and electrochemical impedance spectroscopy (EIS) confirmed that the coatings provided varying levels of corrosion protection depending on the coating deposition temperature. By increasing the deposition temperature and corresponding growth in coating thickness the corrosion current density of the coated magnesium was 10,000 fold lower compared to the bare metal; indicating significantly enhanced corrosion performance of Mg substrate, reaching the corrosion protection requirement for magnesium implant. The barrier effect of Ca-P layers was further supported by the observed magnitude of anodic and cathodic Tafel slopes. Coated samples displayed much larger slopes than bare Mg substrate. EIS results showed that the size of capacitance loops and the absolute impedance value (|Z|) increases. By increasing the deposition time the corrosion mechanism was changed as a result of partial delamination of top surface of coating. In agreement with the electrochemical experiments, immersion tests in SBF also indicated large improvement in corrosion protection as the mass loss was reduced almost three times when coating was applied as compared to the bare metal. The uncoated Mg substrate undergoes severe and non-uniform corrosion after 28 days immersion in SBF solution; while, the coated samples displayed intact coating and no obvious pits were observed on the coating surface. The described biocompatible and biodegradable coatings significantly improved corrosion resistance of Mg substrate and can be promising candidate for biomedical application. Keywords: Magnesium, Calcium-Phosphate coating, Corrosion resistance, EIS

Control of the Corrosion of Magnesium for Implant Application by Hydrothermally Deposited Biodegradable Calcium Phosphate Coating

The corrosion protection of hydrothermally deposited calcium phosphate coatings on AZ31 magnesium alloy was studied in simulated body fluid (SBF) solution for their potential use as biodegradable implants. The coating mainly consisted of bioresorbable monetite phases. Potentiodynamic and electrochemical impedance spectroscopy (EIS) confirmed that the coatings provided varying levels of corrosion protection depending on the coating deposition temperature. By increasing the deposition temperature and corresponding growth in coating thickness the corrosion current density of the coated magnesium was 10,000 fold lower compared to the bare metal; indicating significantly enhanced corrosion performance of Mg substrate, reaching the corrosion protection requirement for magnesium implant. The barrier effect of Ca-P layers was further supported by the observed magnitude of anodic and cathodic Tafel slopes. Coated samples displayed much larger slopes than bare Mg substrate.EIS results showed that the size of capacitance loops and the absolute impedance value (|Z|) increases. By increasing the deposition time the corrosion mechanism was changed as a result of partial delamination of top surface of coating. In agreement with the electrochemical experiments, immersion tests in SBF also indicated large improvement in corrosion protection as the mass loss was reduced almost three times when coating was applied as compared to the bare metal. The uncoated Mg substrate undergoes severe and non-uniform corrosion after 28 days immersion in SBF solution; while, the coated samples displayed intact coating and no obvious pits were observed on the coating surface.The described biocompatible and biodegradable coatings significantly improved corrosion resistance of Mg substrate and can be promising candidate for biomedical application.

Duplex processing for increased adhesion of sputter deposited Ti1-xAlxN coatings on a Fe–25%Co–15%Mo tool material

Recently, carbide-free alloying systems with yield strength Rp0.1 of up to 4000MPa and outstanding thermal stability are available, which offer the possibility to elevate coating deposition temperatures up to 600°C. The present work demonstrates that the limited Ti1−xAlxN coating adhesion on a Fe–25%Co–15%Mo grade caused by the absence of carbides in the substrates can be significantly improved from HF 4 to HF 2 in the Rockwell adhesion test by plasma-assisted nitriding during sputter etching. X-ray photoelectron spectroscopy measurements reveal that the nitrogen diffusion zone is confined to the first few nanometre of the substrate surface, while mainly Mo–N and partly Fe–N bondings are formed. X-ray diffraction exhibits the formation of cubic Mo2N in the nitrided layer. The coatings show a single-phase face-centered cubic Ti1-xAlxN structure tending to a preferred (110) growth orientation with increasing nitriding time. Tribological tests performed at room temperature and 650°C indicate superior wear performance of duplex Ti1-xAlxN coated Fe–25%Co–15%Mo.

Nanocomposite and nanostructured superhard Ti-Si-B-N coatings

Electron microscopy, x-ray diffraction analysis, and micro-and nanohardness measurements were used to investigate the interrelations between the fine structure and the variations in strength properties of nanostructured and nanocomposite Ti-Si-B-N coatings with high oxygen and carbon contents. It has been shown that under the conditions of low-temperature (T = 200°C) coating deposition, a two-level grain structure forms with {200} texture and grains 0.1–0.3 µm in size fragmented into subgrains 15–20 nm in size. As the silicon content is increased, textureless coatings with the crystal phase grain size less than 15 nm and high amorphous component or coatings of amorphous-crystalline structure are produced. At coating deposition temperatures of 400–450°C, a nanocomposite structure with a grain size d = 10–15 nm and no texture is observed. For all test compositions and conditions of coating production, a Ti 1−x Si x N crystal phase with the lattice parameter a = (0.416–0.420) ± 0.001 nm has been detected. For optimum coating compositions and synthesis conditions, the hardness is over 40–50 GPa. It has been supposed that superhardness can be attained with multiphase grain-boundary interlayers of thickness more than 1 nm.

Multicomponent hard and superhard submicro- and nanocomposite coatings on the basis of titanium and iron nitrides

Electron microscopy, X-ray structure analysis as well as micro- and nanohardness measurements are used to study the relation between the fine structure and variation of strength properties of nanostructured and nanocomposite Ti-Si-B-N and Ti-Al-Si-N coatings with high oxygen and carbon content. For all studied alloys and deposition modes we have revealed the crystalline phase Ti 1- x Si x N with the lattice parameters a = (0.416-0.420) ± 0.001 nm. In the conditions of low-temperature (T = 200 °C) coating deposition a two-level grain structure with the fragmentation of 0.1-0.3 μm grains into 15-20 nm subgrains and with {200} texture is formed. The generality of the conclusion about the two-level grain structure formation at a columnar growth of the coating is substantiated for (Fe, Cr, Ni) 4 N coatings. With silicon content growth texture-free coatings with lattice grain size less than 15 nm and high fraction of the amorphous phase are formed. At coating deposition temperatures 400-450 °C one can see a nanocomposite structure with the grain size d = 10-15 nm and no texture. At optimal compositions and synthesis conditions the hardness values exceed 40-50 GPa. We suppose that it is possible to achieve superhardness for multiphase grain boundary interlayers more than 1 nm thick.

Enhanced Performance of Pennzane® Greases for Space Applications by Both Additive Formulations and Smooth Hard Coatings

Tribological requirements of the moving mechanical assemblies (MMAs) of spacecraft are usually satisfied by a variety of lubricants and materials. When the lubricant elastohydrodynamic film is broken, metal-to-metal contact occurs in the MMAs. This may lead to lubricant overheating, and breakdown, and then to increased wear and failure. Wear related failure can also occur due to evaporation and/or creep of the lubricant over the lifetime of space assembly. As requirements for spacecraft performance and lifetime increase, improved lubrication systems for MMAs are needed. A considerable amount of progress has been made in developing improved lubricants with advanced additives; however, their performance has not been evaluated and ranked. In the present work, four-ball and reciprocating tribometer tests were conducted to evaluate and rank the performance of various Pennzane® based greases. Employing the reciprocating tribometer technique, Pennzane® based greases were also evaluated with hard coatings such as titanium nitride (TiN) and titanium carbonitride (TiCN) in a metal-on-coating configuration. Viability of a filtered cathodic arc technique for obtaining very smooth, hard coatings is demonstrated. The importance of coating deposition temperature for certain bearing steel materials is also discussed. It is demonstrated that wear is substantially reduced with an optimized Pennzane® grease formulation on a smooth, hard TiCN surface coating.

Effect of coating deposition temperature on monazite coated fiber

Monazite (LaPO 4) was continuously coated on 3M Nextel ™ 720 fiber tows with an ethanolic precursor using hexadecane for immiscible liquid displacement. Coating deposition temperatures were varied from 900 to 1300°C. Fibers coated at 900°C were heat-treated up to 100 h at 1200°C. Coated fibers were characterized by analytical TEM, and tensile strengths were measured by single filament tensile tests. The monazite precursor was characterized by X-ray, DTA/TGA, and mass spectrometry. Microstructure evolution was complex and may have involved recrystallization of large defective grains into smaller grains and then subsequent growth of these grains, along with coarsening of porosity. After 100 h at 1200°C there was significant roughening of the coating–fiber interface, with facetting of alumina grains in the fiber and some lanthanum segregation to these facetted boundaries. Spheroidization of thin coatings was also observed. Tensile strength of coated fiber decreased with increasing deposition temperature and with time at temperature after deposition. Possible reasons for the strength decrease are discussed.

Effect of stress concentration on the mechanical properties of molybdenum sheet with protective coatings

1. Under conditions of brief static loading molybdenum sheet of grade MCh-II was found to be almost insensitive to stress concentrations (for the selected types of concentrators). 2. The presence of a diffusion protective coating leads to a considerable decrease in the ductility of the material over the whole investigated range of temperatures and to a decrease in its strength at temperatures below the coating deposition temperature. 3. It was established that the strength of specimens with protective coatings in the presence of stress concentrators is higher than the strength of smooth specimens with the same coatings.