High-strength Coatings Research Articles

Ceragenin-CSA13 loaded high strength coatings of nano- and micro-SrHA implanted N-Carboxymethyl chitosan – Polyetheretherketone by low temperature high speed collision approach: In vitro pro-osteogenicity and bactericidal activity against MRSA

Cationic steroid antimicrobials (CSA13) loaded in the uniform coatings synthesized by micro and nano sized particles of strontium substituted hydroxyapatite implanted into the surface of N-carboxymethyl chitosan (N-CMCh) pre-embedded on polyetheretherketone (PEEK) substrate and their biocompatibility and antibacterial efficacy were investigated. Release of CSA13 from the nano SrHA implanted substrate showed faster release of the drug till 48 h with a release of 48% of total drug. It was found that CSA13 rich nano SrHA implanted substrate damaged the Methicillin Resistant Staphylococcus Aureus biofilm mass in 30 h, while micron sized SrHA implanted substrate reduced the biofilm mass to 27% at the same culture period. MG63 cell viability on these specimens exhibited significant cell growth even in the presence of CSA13. Nano SrHA implanted substrate showed better biocompatibility simultaneously providing antibacterial efficacy than the micro sized coating. The sustained release of CSA13 from the nano Sr-HA coating could be beneficial for long term eradication of infection. In silico docking approach between CSA13 and 1VQQ penicillin binding protein 2a from MRSA strain showed strong negative binding energy of (−) 68.78 kcal/mol demonstrating an in-visual predicting anti-bacterial efficacy.

Engineered Aluminum Powder Microstructure and Mechanical Properties by Heat Treatment for Optimized Cold Spray Deposition of High-Strength Coatings

Engineered Aluminum Powder Microstructure and Mechanical Properties by Heat Treatment for Optimized Cold Spray Deposition of High-Strength Coatings

Study on the Influence of Polymer/Particle Properties on the Resilience of Superhydrophobic Coatings.

Enhancement in the resilience of superhydrophobic coatings is crucial for their future applicability. However, the progress in this aspect is currently limited due to the lack of a consistent resilience analysis methodology/protocol as well as the limited understanding of the influence of the materials components on the resultant coating performance. This study applies a quantitative analysis methodology involving image analysis and mass tracking and utilizes it to investigate how the properties of coating components can influence coating resilience. The factors examined were changing the molecular weight/tensile strength of poly(vinylchloride)/poly(dimethylsiloxane) (PVC/PDMS) polymers and changing the size of the roughening particles. In addition to the examination of resilience data to evaluate degradation patterns, three-dimensional (3D) mapping of the scratches was performed to obtain an insight into how material removal occurs during abrasion. The results can indicate preferential polymer selection (using higher-molecular-weight polymers for PVC) and optimal particle sizes (smaller particles) for maximizing coating resilience. The study, although focused on superhydrophobic materials, demonstrates wide applicability to a range of areas, particularly those focused on the development of high-strength coatings.

Контактна взаємодія частинок з поверхнею основи при газотермічному напиленні

Показана роль контактної взаємодії частинок, що напилюються, з основою у формуванні міцних газотермічних покриттів. В якості основних структуроутворюючих елементів в покриттях прийняті сплети – поодинокі напилені частинки. Проаналізовано основні фактори, що визначають структуру і властивості газотермічних покриттів в процесі напилення, причому найважливішу роль відіграє утворення контакту частинка – основа і процеси, що протікають на ньому. Проаналізовано основні фактори, що визначають взаємодію матеріалів частинки та основи. Розглянуто основні роботи, присвячені проблемі схоплювання частинок з основою при напиленні. Запропоновано при аналізі утворення фізичного контакту розглядати площу контакту, що утворюється, з урахуванням розмірів напилюваних частинок і наявності на поверхні основи мікро- і наношорсткості чотирьох рівнів: номінальної, контурної, фактичної і фізичної. Фізична площа контакту на кілька порядків менше контурної площі та на її площадках формуються найбільш міцні адгезійні зв'язки. Запропоновано рівняння для оцінки фізичної площі контакту в зоні дії напірного тиску.

Bridges maintainability evaluation peculiarities as part of hydraulic structures

Introduction: the article is dedicated to assessing the condition with respect to use for traffic methods of bridges as part of hydraulic structures (dams, hydroelectric power stations, locks). The main factors affecting the structural element’s durability included in the composition of the hydraulic structures are dynamic loads (applied repeatedly and repeated) affecting the bay due to the hydrodynamic effect; temporary, moving loads from passing highway transportation, along the top of the structure (along the roadway); harmful chemical impurities contained in the water passing through the structure. Under the influence of the above-mentioned factors, defects and damage occur in the hydraulic facilities’ structural elements. Methods: the authors assessed the actual state of the material of the operating structure. To assess structures and materials actual state during the bridge structure inspection work, the following instrumental measurements were performed on as-built structural elements: leveling the top of the sidewalks and the roadway; materials strength determination of the main supporting structures by nondestructive methods; thickness measuring the asphalt concrete pavement of the roadway; determination of the degree of carbonation of concrete; identification of defects in the elements of the bridge. The actual structure’s concrete strength was determined by nondestructive testing methods: (1) by the method of the elastic rebound; (2) by the shock pulse monitoring method; (3) an indirect method of concrete strength ultrasonic testing based on the revealed relationship between the method of separation with shear test and methods – shock pulse and elastic rebound. Results: technical condition and bridge safety indicators calculation as a hydraulic structure element was executed. Discussion: technical examination results of the bridge structural elements and instrumental studies confirm the conclusion about the repair measures need with high-strength concretes and protective coatings based on polymer composite materials. Final report: following the emergency scenarios a numerical estimate table for the quantitative and qualitative parameters list was made, parameters corresponding to a particular structure state. Thus, according to the scenario related to the 3rd accident group, the bridge technical condition is assessed as limited operable, and the safety level is reduced.

The use of ash-mineral mixtures for the construction of high-strength coatings of forest roads

Forest roads are characterized by difficult transport and operating conditions and a considerable distance from sources of traditional road-building materials. Local ash and slag waste of the state district power station is an effective road-building material for the construction of forest roads. The article presents the test results of the building properties of the ash of the Reftinskaya TPP and the physicomechanical characteristics of the ash-mineral mixtures prepared with its use. Based on the results of laboratory studies, technical solutions for the use of ash-mineral mixtures in the design and construction of high-strength coatings of forest roads have been developed: the main design indicators, requirements for the materials used in the composition, approximate compositions of the ash-mineral mixtures are given, technical measures for the organization and quality control of construction work are assigned.

Principles for creation of high-strength coatings for friction units

The concept for creating of high-strength coatings based on the structural theory of strength is proposed. It allows purposefully forming structure, that can effectively resist wear and fatigue. Surface laser alloying of steels with subsequent nitriding is studied. The increase in surface hardness, strength, wear resistance by 15 times and crack resistance by 1.5 times is shown in comparison with the standard parameters of steels.

Experimental evaluation of interfacial adhesion strength of cold sprayed Ti-6Al-4V thick coatings using an adhesive-free test method

Cold spray (CS) is a rapidly growing solid-state additive material deposition technique often used for repair of high-value metallic components. This study aims at evaluating the interfacial adhesion strength of cold sprayed Ti-6Al-4V (Ti-64) coatings deposited onto Ti-64 substrates for repair applications. An adhesive-free test method, referred as modified Collar-Pin Pull-off Test was developed based on Sharivker's (1967) original design, in order to overcome the limitations of existing test approaches (both adhesive-based and adhesive-free). This method was designed to allow measurement of adhesion strength of high strength coatings such as CS Ti-64, where adhesion strength is higher than 70–90 MPa. A parametric study was performed to assess the effect of coating thickness, scanning speed, track spacing, toolpath pattern, and substrate surface preparation on the coating adhesion strength. A finite element model was also used to evaluate the stress distribution during the pull-off test, and to check the validity of the proposed test method. The proposed adhesive-free test method was found to be capable of measuring coatings with adhesion strengths beyond the upper limit of conventional adhesive-based methods such as ASTM C633. Among the investigated cases, the highest value of coating adhesion strength was measured around 122 MPa, in the case of CS Ti-64 deposited on ground Ti-64 substrates.

Formation of Coatings on Titanium Alloys by Melting with a Beam of Relativistic Electrons

High-strength coatings deposited on billets of titanium alloy VT1-0 by the method of electron-beam melting of a mixture of boron carbide, titanium and fluorine flux powders are studied. Metallographic and x-ray diffraction analyses and wear tests of specimens with modified layers are performed, and the microhardness of the coatings is determined. The microhardness of the surface and the wear resistance of alloy VT1-0 grow considerably after the deposition of coatings from a powder mixture with 30% boron carbide.

Producing hardfacing composite materials for ecologically safe technologies

The application of hardfacing materials for producing high-strength coatings on components working in abrasive wear conditions is one of the important directions of research into increasing the service life of road construction, agricultural and other types of equipment. However, in producing this equipment, the ecological safety requirements are sometimes ignored and this results in negative effects on the environment and the health of personnel. This article describes the results of scientific and research investigations of the team of authors to develop a cladding powder by the method of chemical gas phase deposition of nickel tetracarbonyl on the surface of aluminium oxide particles and application of the powder for producing wear-resistant coatings. The powder materials are deposited in a closed cycle excluding contact of the personnel with toxic substances and emission of contaminants into the atmosphere, resulting in a safe process. Plasma coatings with the required physical–mechanical properties have been produced. This confirms the efficiency of the approaches used in this case and increases the service life of working sections of machines subjected to abrasive wear.

Comparison of TiN-coated tools using CVD and PVD processes during continuous cutting of Ni-based superalloys

Abstract High-strength, low-conducting Ni-based superalloys require higher cutting force and cutting temperature than other materials during the machining process. To understand how the coating characteristics such as defects formation and physical and mechanical properties affect cutting performance, TiN coatings were deposited by three physical vapor deposition (PVD) methods (arc ion plating, sputtering, and hollow cathode) and chemical vapor deposition (CVD). Sputtering and CVD yielded TiN coatings with fewer defects than other methods. Subsequently, the damage to the TiN coatings during machining of alloy 718 was investigated under continuous turning. Tools coated by sputtering and CVD exhibited micro-abrasion wear without heavy fracture or delimitation of the coating. Furthermore, the CVD coating showed the best cutting performance and lower plastic deformation than the PVD coatings. TiN coatings were characterized by X-ray diffraction, nanoindentation, electron back-scatter diffraction, and transmission electron microscopy. As the hardness of the coatings was measured before and after heat treatment, the CVD coating was more resistant to softening due to heating than the PVD coatings. The reduced hardness of the PVD coatings was attributed to strain release, atomic rearrangement, and grain growth in the PVD coatings. Such high-strength coatings with good high-temperature stability and low-defect density offer strong protection to cutting tools during machining of Ni-based superalloys. Based on the results of this study, fine structure CVD-deposited coatings may be good candidate coating for cutting of the Ni-based superalloys.

FEM Analysis and Experimental Study for Bond Strength of High-Strength Coating by Wedged Load Test Method

A wedged load test method is used to evaluate the adhesion strength of high-strength coatings, which have been processed with various sintering parameters. In this test, for stress concentration at cut tip, cracks are always induced and expanded rapidly cross the interface between coating and substrate. Macro-fracture and SEM image of coating interface of high-strength coating are characterized using optical microscope and scanning electron microscopy (SEM), respectively. In order to evaluate the bonding properties between coating and substrate effectively, corresponding finite element (FE) analysis has been conducted to evaluate the adhesion strength of high-strength coating. And stress distributions cross the interface of high-strength coating are obtained. The stress analysis can help to evaluate the bond strength of high-strength coating. Because of small specimen and contact relationship between wedged pressure head and wedged cuts, complex stress state is affected by many factors resulting from interface, and also by the thickness of coating.

Mechanical properties of reticulated aluminum foams with electrodeposited Ni–W coatings

The struts of reticulated aluminum foams were coated with nanocrystalline Ni–W by electrodeposition. The thickness and composition of these high-strength coatings are controlled by varying the bath chemistry, applied current conditions and deposition time. Despite an increase in density as compared to the uncoated foams, the coated foams exhibit improvements in both absolute and specific strength, as well as in absolute energy absorption.

Change in internal friction in coated specimens during wear

The present paper is devoted to the laws of change in the vibration decrement in the process of wear of high-strength coatings and the effect of its restoration in heating of coated specimens damaged to various degrees under friction.

Formation of high-strength metallic coatings by pulse plating

We present the results of experimental investigation of high-strength multilayer metallic coatings deposited by pulse currents. It is shown that both monometallic (nickel, zinc, and copper) and composite (tinnickel, tin-copper, and copper-nickel) multilayer electroplated coatings exhibit better characteristics of strength than their components. We discuss possible causes of this phenomenon.

Real Time Observation of Material Deformation Processes by Synchrotron White Beam X-ray Topography

ABSTRACTAn experimental apparatus which exploits synchrotron white beam X-ray diffraction topography has been developed to perform real time in situ observation of deformation processes of single crystals. The apparatus consists of a fully automated and remotely controlled mini-tensile device and a CCD based X-ray imaging detector with associated video system. Both tensile data and X-ray topographic images are recorded simultaneously. The materials under study include single crystals of Si, and single crystals or bicrystals of the refractory metals W and Mo. The deformation processes of these crystals have been studied by monitoring a selected transmission Laue spot while the specimen is mechanically cycled by loading and unloading. The X-ray images have been captured by a frame grabber and recorded via a VCR. Several phenomena have been observed, including bending contours, strain concentrations, reversible anelastic effect and microyielding. The observed stress relaxations are correlated to microstructural variations shown by X-ray topography. The stability of low angle grain boundaries in bicrystals; and the effect of high strength and toughness coatings on the deformation of single crystal substrates was investigated.

Tensile Properties and Bond Strength of Polyamide Coatings Produced by Thermal Spraying

SummaryA modified flame spray coating system has been developed. The new process can be applied to powdered thermoplastic and thermoset polymers without special requirements or post-fusing process, producing high bond strength and high density coatings as with plasma spray. Polymer materials can be sprayed onto steel substrates, even for on-site use. The influence of parameters on properties of Polyamide coatings is investigated in the present paper.

Regular features of wear in heterogeneous structures of high-strength coatings

High-strength coatings on alloys of various morphology prepared by methods of surface impregnation are effective (wear resistant) in operation and economical in production. The requisite structure, wear resistance, and antifriction properties can be provided by a proper choice of the production technology of the coating and the quality parameters of the triboengineering layers, which determine the operating capacity, namely, the geometric (thickness of the coating and depth of the diffusion zone), structural (porosity, phase composition, substructural components), and physical and mechanical (macro- and microstresses, microhardness) parameters and the strength of cohesion with the substrate.

Structural aspects of increasing the efficiency of coatings made of high-strength materials

Nitrides and carbides of transition metals are used as an example to examine the failure resistance of coatings of high-strength materials which, in comparison with metals, are characterized by high strength and satisfactory brittle fracture conditions. Using synergetics approaches, it is confirmed that high reliability of these coatings can be achieved if their structure contains closed discrete regions of a ductile metallic material which ensure during loading partial scattering of energy by means of plastic deformation. This assumption has been confirmed by experimental formation in the TiN 1−x -Ti system of high-strength coatings with the so-called window structure.

The use of high-strength vacuum-deposited coatings as a means of protection against wear

It was shown that the wear resistance of high-strength vacuum-deposited films is considerably higher than that of electrodeposited coatings or case-hardened steel. The wear resistance of vacuum-deposited coatings may vary within wide limits depending on the deposition conditions.