Maryana Zagula-Yavorska

Microstructure and oxidation behaviour investigation of rhodium modified aluminide coating deposited on CMSX 4 superalloy

The CMSX 4 superalloy was coated with rhodium 0.5‐μm thick layer and next aluminized by the CVD method. The coating consisted of two layers: the additive and the interdiffusion one. The outward diffusion of nickel from the substrate turned out to be a coating growth dominating factor. The additive layer consists of the β‐NiAl phase, whereas the interdiffusion layer consists of the β‐NiAl phase with precipitates of σ and μ phases. Rhodium has dissolved in the coating up to the same level in the matrix and in the precipitates. The oxidation test proved that the rhodium modified aluminide coating showed about twice better oxidation resistance than the nonmodified one.

The Effect of Zirconium Addition on the Oxidation Resistance of Aluminide Coatings

Nickel, Mar M247, and Mar M200 superalloys were coated with zirconium-doped aluminide deposited by the chemical vapor deposition method. All coatings consisted of two layers: an additive one, comprising of the β-NiAl phase and the interdiffusion one. The interdiffusion layer on pure nickel consisted of the γ′-Ni3Al phase and β-NiAl phase on superalloys. Precipitations of zirconium-rich particles were found near the coating’s surface and at the interface between the additive and the interdiffusion layer. Zirconium doping of aluminide coating improved the oxidation resistance of aluminide coatings deposited both on the nickel substrate and on the Mar M200 superalloy. Precipitations of ZrO2 embedded by the Al2O3 oxide were formed during oxidation. It seems that the ZrO2 oxide increases adhesion of the Al2O3 oxide to the coating and decreases the propensity of the Al2O3 oxide rumpling and spalling.

Degradation of nonmodified and rhodium modified aluminide coating deposited on CMSX 4 superalloy.

The Ni‐base superalloy CMSX 4 used in the turbine blades of aircraft engines was coated with rhodium layer (0.5‐μm thick). Next coated CMSX 4 superalloy was aluminized by the CVD method. The rhodium modified aluminide coating and nonmodified aluminide coating were oxidized at 1100°C at the air atmosphere. The rhodium modified aluminide coating showed about twice better oxidation resistance than the nonmodified one. The spallation equal 62% of the total area was observed on the surface of the nonmodified coating whereas only 36% spallation area was observed on the surface of the rhodium modified aluminide coating after the oxidation test. The oxide layer formed on the surface of the nonmodified coating was composed of nonprotective (Ni,Cr)Al2O4 and (Ni,Cr)O phases. Aluminium in the coating reacts with oxygen, forming a protective α‐Al2O3 oxide on the surface of the rhodium modified aluminide coating. When the oxide cracks and spalls due to oxidation, additional aluminium from the coating diffuses to the surface to form the oxide. The presence of protective Al2O3 oxide on the surface of the rhodium modified aluminide coating slows coating degradation. Therefore, rhodium modified aluminide coating has better oxidation resistance than the nonmodified one.

The Ni-Al-Zr Multiphase Diffusion Simulations

Abstract The generalized Darken method allows a quantitative description of diffusion mass transport in multi-phase materials. The method characterizes the diffusion zone by phase volume fractions. The results of the calculations are compared with experimental concentration’s profiles of nickel, zirconium and aluminum in zirconium doped aluminide coatings deposited on pure nickel by the PVD and CVD methods.

The Effect of the Aluminide Coating on the Thermal Properties and Oxidation Resistance of Inconel 625 Ni-Base Superalloy

An investigation was conducted to synthesize βNiAl coating on the nickel based superalloy Inconel 625 in the low activity chemical vapor deposition process (CVD). The deposition was carried out for 8 hours at 1050°C using the BPXpro3252 IonBond company equipment. Surface morphology and cross-section microstructure of the diffusion coating were studied and compared using an optical microscope, an X-ray diffractometer and a scanning electron microscope (SEM) equipped with an energy dispersive spectroscope. It was found that 29 μm thick aluminide coating consisted of two layers: an outer one and the inner interdiffusion one. The outer layer consisted of the βNiAl phase. The inner one consisted of the βNiAl phase with chromium, molybdenum and niobium carbides (M23C6 and MC type) inclusions. Outer layer hardness was about 564 HV0.002 while interdiffusion layer hardness was about 725 HV0.002. Thermal diffusivity of Inconel 625 superalloy with and without coating was measured using a NETZSCH model 427 laser flash diffusivity apparatus. The thermal diffusivity measurements were conducted in the argon atmosphere at the temperature interval 20 - 1200 oC. Thermal diffusivity of the uncoated Inconel 625 Ni-base superalloy at the room temperature is about 2 mm2/s, while for the coated superalloy thermal diffusivity is about 2.8 mm2/s. The increase of the temperature from 20 to 1200 oC leads to the increase of the thermal diffusivity of the coated sample from 2.8 to 5.6 mm2/s. Cyclic oxidation tests for both coated and uncoated superalloys were performed at 1100°C for 1000 h in the air atmosphere. The aluminized samples exhibited a small mass increase and the α-Al2O3 scale was formed during the oxidation test.

SEM/TEM Investigation of Aluminide Coating Co-Doped with Pt and Hf Deposited on Inconel 625

The effect of simultaneous introduction of Hf and Pt into aluminide coating deposited on Inconel 625 alloy was investigated using scanning and transmission electron microscopy (SEM/TEM) methods. The coating consisted of two layers: the additive and the interdiffusion. The additive layer and part of the interdiffusion layer consist of the β-NiAl type phase. The middle part of the interdiffusion layer comprised an interpenetrating finger-like structure formed by the β-NiAl and TCP—σ type phases with numerous fine Cr precipitates in the former and occasional larger precipitates of NbC carbides interspersed in between them. The σ type phase inclusions are situated at the border between the substrate and the interdiffusion layer. The experiment showed that platinum fully dissolves in the β-NiAl-type matrix, while most of the introduced hafnium accumulates in HfO2 dioxide precipitates located close to the additive/interdifusion interface.

Hafnium and palladium modified aluminide coatings

D of biodegradable materials is highly in demand as large and rapid usage of plastic materials results million tons of plastic wastes in the landfill sites each year globally. It takes a long time for conventional plastics to degrade, leading to severe ecological problems too. The production capacities of biodegradable plastics, such as polylactic acid (PLA), polyhydroxyalkanoates, and starch blends, are also growing steadily, nearly doubling from 0.7 million metric tons in 2014 to well over 1.2 million metric tons by 2019. PLA, for its good compatibility and biodegradability, is preferred by people from all sectors. Also, PLA is a low energy consumption product, about 30-50% lower in energy consumption than the petroleum-based polymers. PLA as the most widely used, the lowest price of bioplastic in industrialization, in the aspect of practicality, is the biodegradable material that has the largest scope to replace the position of the petroleum based plastics on the current scenario of oil scarcity. The production cost of PLA is also approaching the cost of traditional plastic, and with the strong expansion of market applications, will get soon recognized globally. PLA based nanocomposites are widely used today in various applications. The review article aims to target on the topical progresses in the synthesis and characterization of PLA blends, PLA composites and PLA nanocomposites with different materials. Moreover, this article is a unique collection of vital information about PLA based blends and composites for drug delivery, packaging and barrier applications in a single platform.D intensive research and applications of different techniques to improve surface properties of vascular stents, currently available metal stents and their coatings (DES drug eluting stents) still lack of desired surface biocompatibility, mostly due to mechanical injuries, inflammation, as well as proliferation and migration of smooth muscle cells, often with progression to restenosis. Besides, the durability and stability of DES is still problematic and has been connected with high risk of thrombosis Biomimetic nanosized materials, with their crystal structure, surface morphology and chemical properties are one of critical features for their potential use in vascular stent applications, which should support adhesion, proliferation and differentiation of endothelial cells and prevent abnormal growth of smooth muscle cells. For example, it was shown that titanium dioxide (TiO2) nanotubes (NTs) topography is essential parameter in optimizing endothelial cell and smooth muscle cell responses to vascular implants. The purpose of this study is to investigate surface properties and crystal structure of TiO2 NTs. Since the oxygen, plasma treatment plays significant role in surface treatment of biomedical devices due to surface cleaning and sterilization, its effect on the mechanical stability and surface chemical properties was evaluated. Vertically aligned arrays of TiO2 NTs were synthesized on Ti metallic substrates with electrochemical anodization. The crystal structure was investigated with X-ray Diffraction Spectroscopy, while morphology and surface properties were analyzed with Scanning Electron Microscopy coupled with Energy Dispersive X-ray Analysis, X-ray Photoelectron Spectroscopy and Water Contact Angle analysis. Our results indicate that oxygen plasma treatment of TiO2 NTs surfaces induces the formation of oxide layer on the surface of TiO2 NT, which could result in enhanced biocompatibility. Moreover, plasma treatment removes undesired electrolyte residues on TiO2 NTs surface and highly improves its wettability. We showed that plasma treated TiO2 NTs possess long-term hydrophilicity and influence on crystallization of amorphous TiO2 NTs to anatase and/or rutile crystal phase, which could be the reason for improved wettability. The optimized conditions (power, frequency and time) of oxygen plasma treatment on the mechanical stability of TiO2 NTs are also presented. Oxygen plasma treatment can greatly improve the surface characteristics of biomimetic materials and enhance their biocompatibility. Restenosis and thrombosis still remain a serious concern and should be given a great deal of attention in order to produce improved tissue-material response.Resumen del trabajo presentado a la 11th International Conference on Advanced Materials & Processing, celebrada en Edimburgo (Escocia) del 7 al 8 de septiembre de 2017.P of thin lead zirconate titanate (PZT) films on metallic substrates has several advantages such as high frequency operation, low electrical series resistance, low dielectric loss and potential for embedded capacitor systems. As a suitable metal support for PZT films, titanium (Ti) seems to be the most natural choice as it possess high melting point, the thermal expansion coefficient of Ti matches closely to that of PZT and permits good adhesion with low reactivity. However, ferroelectric and piezoelectric responses of PZT films on Ti substrates are found to be not that encouraging. Presence of a non-ferroelectric pyrochlore/ fluorite (Py/Fl) phase on the surface of the PZT film is believed to be the primary cause for poor electrical performance. In this work, effect of re-crystallization of PZT films with a thin Pb-overcoat has been investigated though structural, morphological, compositional and electrical studies. Sputter deposited PZT thin films on Ti-substrates are found to contain a Pb-deficient and Zr-enriched Py/Fl phase of type Pb2 (Zr,Ti)2O6 on the surface of the PZT film. Re-crystallization of these PZT films with a thin lead (Pb) overcoat improves the degree of crystallization, morphology and dielectric/ Ferroelectric properties of the films by converting the top Pb-lean and Zr-rich Py/Fl phase into perovskite phase. Structural changes that occur in PZT films upon re-crystallization with a Pb-overcoat have been correlated with ferroelectric characteristics of the PZT films.P nanoparticles have a broad spectrum of applications including dispersion (emulsion) paints or thin films. However, the understanding of their behavior and properties, especially at high concentrations is still limited. We model the dispersions of polymeric nanoparticles using the dynamic model based on Discrete Element Method (DEM). The interaction model represents particles that are elastic, adhesive and electrostatically stabilized. The flow-field computation that is included in the model enables us to evaluate the rheological properties of the dispersion, which are crucial for its behavior. Further characterization of both dispersions and gels is done using oscillatory simulations, from which the viscoelastic properties are obtained. The model was successfully used to describe the dynamic behavior of a flowing dispersion including the processes of coagulation, fouling and breakage. These processes and their relative importance in a specific system determine the transition from a dispersed state to a gel. Due to their specific position on the boundary between solids and liquids, gels have unique properties that make them suitable to be used e.g., as a porous structures (or) matrices for drug delivery in the pharmaceutical industry.O surgery has grown from the hand of new materials that made possible to perform procedures as total hip replacement with feasibility. These procedures are common in most orthopaedic departments, and more than 70 000 hip or knee replacements are performed in Spain every year. The survival of these implants is critical to prevent loosening and the need for revision arthroplasty. The ideal surface to interact with bone has not been created. We created laser induced periodic surface structures (LIPSS) in the surface of titanium and tantalium to study the behaviour of stem cells compared to polished surfaces. We created 12 discs of each material and polished them. Later we created LIPSS in 6 discs of each material. We cultured them in human stem cells in a concentration of 25000 cell per cm2 for 20 days. We determined MTT, TNF-Alfa, alkaline phosphatase, IL-6, osteopontin and osteocalcin every 5 days until the day 20. We confirmed outcomes behave as a normal distribution after applying the Kolmogorov Smirnov test. We compared materials and surfaces with the T-student test. We accepted a difference of 0.05 as significant. LIPSS created increase statistically cell metabolism (best values in MTT assay) and decrease inflammatory response to the material (IL-6 and TNF-alfa values). Collagen is produced in more quantity and cells differentiate to osteoblast easily. These differences are seen from the beginning until the endpoint (day 20). When LIPSS improved osteogenic properties of titanium and tantalium compared to smooth surfaces.I the last 5 years, methylammonium lead halide or MALH perovskites (e.g., CH3NH3PbA3-xBx, where A and B are I, Cl or Br) have shown tremendous potential for low-cost optoelectronic device integration, including light-emitting diodes, solar cells and photodetectors. For example, the power-conversion efficiencies from organometallic halide perovskite solar cells have increased from 3.8% in 2009 to 22.1% in 2016. This spectacular progress is largely attributed to improved processing and longer chargecarrier lifetimes, directly related to increased material quality. While significant progress was made, many key parameters including compatibility, interface engineering, surface treatment and processability remain essential to achieving the best device performances. These fundamental challenges prevent integration into commercial-grade devices. For one, relatively low carrier mobilities still prevent large-area devices with performances competing with state-of-the-art technologies. Several groups began exploring hybrid perovskite films in the last 3 years. In the last year, we have made major progress towards viable MALH devices (1) by dramatically enhancing structure and properties through solvent engineering, (2) enhancing conductivities by several orders of magnitude using MALH hybrids, (3) extending their operation to the near-infrared and (4) significantly improving their stability and lifetime by doping with SCN. Preliminary results shown in Fig.1 are greatly encouraging and suggest that the carefully-controlled processing capability allowed by the Ceradrop inkjet printer can yield high-quality MALH films. This is a major step towards the integration of MALH perovskites within commercial printable photovoltaic devices, LEDs and sensors.C normally causes damage in hydraulic machineries such as pumps and screw propellers, as severe impacts are produced at cavitation collapses. However, cavitation impacts can be utilized for surface mechanics design for improvement of fatigue strength in the same way of shot peening. The peening method using cavitation impacts is named as “cavitation peening”. The advantage of cavitation peening is that the increase of surface roughness is small comparing with conventional shot peening, as shots are not required in cavitation peening. In order to mitigate stress corrosion cracking, introduction of compressive residual using cavitation impact was proposed, and it has been applied for nuclear power plants. By enhancing cavitation impacts, improvement of fatigue strength was demonstrated.The aspect of cavitation peening of gear by using a submerged water jet with cavitation, i.e., a cavitating jet. In order to investigate mechanism of improvement of fatigue strength, a special fatigue tester was developed to investigate crack propagation in surface modified layer. Cavitation peening also suppress hydrogen embrittlement. At laser peening, it is believed that impact caused by laser abrasion produces plastic deformation for surface treatment. However, a bubble is generated after laser abrasion, and it produces impact at bubble collapse like cavitation, then it can be called as laser cavitation. As shown in Fig. 2, when the impact passing through the material was measured, the impact induced by laser abrasion is larger than that of laser abrasion. Namely, at submerged laser peening, peening effect would be improved by considering the laser cavitation. In the presentation, the principal of cavitation peening is introduced with applications of cavitation peening such as improvement of fatigue strength and suppression of hydrogen embrittlement. The work was partly supported by Osawa Scientific Studies Grants Foundation.E of materials subjected to electric current and Joule heating has been studied by many researchers and fruitful results have been reported. In my presentation, crack problems in a conductive material are first discussed. The path-independent integral for an electric crack problem in a plate subjected to current is explained with its relations to Joule heating near the crack tip and the increase in electric resistance of the plate due to a unit crack extension. Regarding nondestructive evaluation of cracks, highly sensitive direct current potential drop technique, that is closely coupled probes potential drop (CCPPD) technique, is explained with its principle and superior characteristics for evaluation of closed cracks. Also evaluation of multiple cracks is mentioned. In the second, a topic in the field of micro and nano materials evaluation is explained, which is a subject of electrical failure of a metallic nanowire mesh due to Joule heating. Characteristic nature of sequential melting of nanowires in the mesh is explained for respective conditions of current control and voltage control. Next, electromigration (EM) phenomenon, which is atomic diffusion due to electron flow in high density, in metallic thin-film materials related to reliability of integrated circuits is discussed, where the effect of passivation on damage suppression is focused. Finally, fabrication of micro materials of wire and sphere is explained as utilization of EM, where the effect of temperature caused by Joule heating on the shape of formed micro material is mentioned. In addition, the other phenomena of atomic migration such as stress migration and ionic migration are discussed in comparison with EM from a few points of view. Electric field and Joule heating are connected with materials science and evaluation on many equipments, machines and structures. As written above, four topics related to these physical quantities are reviewed in this presentation.D the rapid evolution of material science, it remains difficult to deploy new polymers that are inadequate to meet the stringent demands of industrial membrane separations. Polymer membranes must be ultrapermeable, selective, and resistant to both physical aging, and plasticization. Polymers with intrinsic microporosity (PIMs) are ultrapermeable, yet vulnerable to physical aging and plasticization. Here we show that aging and plasticization in PIMs can be switched on and off through compatibility with a microporous polymer, porous aromatic frameworks (PAFs). By replacing bulky methyl groups with smaller hydro groups, we remove the ability of a PIM polymer matrix to interact with PAFs; accelerating both physical aging and plasticization. Meanwhile PAFs tailors physical aging and annihilates plasticization in the original methylated PIM via physical interactions at specific locations on the PIM polymer chains. This benefits hydrogen recovery at realistic operating conditions; enabling the implementation of polymer membranes as a stand-alone separation technology, a paradigm shift from existing hybrid methods.

Effect of the Platinum Electroplated Layer Thickness on the Coatings' Microstructure

Abstract CMSX 4 and Inconel 625 superalloys were coated by platinum layers (3 and 7 μm thick) in the electroplating process. The heat treatment of platinum layers (at 1,050 ˚C for 2 h) was performed to increase platinum adherence to the superalloys substrate. The diffusion zone obtained on CMSX 4 superalloy (3 and 7 μm platinum thick before heat treatment) consisted of two phases: γ-Ni(Al, Cr) and (Al0.25Pt0.75)Ni3. The diffusion zone obtained on Inconel 625 superalloy (3 μm platinum thick before heat treatment) consisted of the α-Pt(Ni, Cr, Al) phase. Moreover, γ-Ni(Cr, Al) phase was identified. The X-ray diffraction (XRD) results revealed the presence of platinum in the diffusion zone of the heat-treated coating (7 μm platinum thick) on Inconel 625 superalloy. The surface roughness parameter Ra of heat-treated coatings increased with the increase of platinum layers thickness. This was due to the unequal mass flow of platinum and nickel.

Numerical Prediction of the Thermodynamic Properties of Ternary Al-Ni-Pd Alloys

Abstract Thermodynamic properties of ternary Al-Ni-Pd system, such as exGAlNPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) at 1,373 K, were predicted on the basis of thermodynamic properties of binary systems included in the investigated ternary system. The idea of predicting exGAlNiPd values was regarded as calculation of values of the exG function inside a certain area (a Gibbs triangle) unless all boundary conditions, that is values of exG on all legs of the triangle are known (exGAlNi, exGAlPd, exGNiPd). This approach is contrary to finding a function value outside a certain area, if the function value inside this area is known. exG and LAl,Ni,Pd ternary interaction parameters in the Muggianu extension of the Redlich–Kister formalism were calculated numerically using the Excel program and Solver. The accepted values of the third component xx differed from 0.01 to 0.1 mole fraction. Values of LAlNiPd parameters in the Redlich–Kister formula are different for different xx values, but values of thermodynamic functions: exGAlNiPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) do not differ significantly for different xx values. The choice of xx value does not influence the accuracy of calculations.

Hafnium Modified Aluminide Coatings Obtained by the CVD and PVD Methods

Zirconium, hafnium or platinum modification of NiAl phase increases the oxidation resistance of diffusion aluminide coatings. Small hafnium addition to aluminide coatings decreases the oxidation rate of nickel superalloys at 1100 °C.The paper presents comparison of structures of hafnium modified aluminide coatings deposited in two different ways on pure nickel. In the first way double layers of hafnium 3 μm thick and aluminum 3 μm thick were deposited by the EB-PVD on the nickel substrate. The double layers were subjected to diffusion treatment at 1050 °C for 6 h and 20 h. In the second method, a hafnium layer was deposited by the EB-PVD method, whereas aluminum was deposited by the CVD method. The obtained coatings were examined by the use of an optical microscope (microstructure and coating thickness) and a scanning electron microscope (chemical composition on the cross-section of the modified aluminide coating). Microstructures and phase compositions of coatings obtained by different methods differ significantly. Diffusion treatment for 6 h leads into formation of the Ni5Hf phase. The elongation of the diffusion time from 6 to 20 h decrease the volume fraction of the Ni5Hf phase. An aluminide coating deposited by the CVD method at 1050 °C at the nickel substrate with prior hafnium layer (3 μm thick) has a triple zone structure. An outer zone consists of the NiAl phase, a middle zone consists of the Ni3Al phase, and the Ni(Al) phase forms an inner zone, close to the substrate. An NiHf intermetallic phase is between the outer and the middle zone, whereas Ni3Hf is between the inner zone and the substrate.