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The problem of simultaneous growth and competition of intermediate phases during reactive diffusion is formulated and solved. In this paper, we compare existing models of steady state reaction diffusion and introduce the new one basing on the bi-velocity method. We extend old problem and propose method based on material (lattice) fixed frame of reference. It allows computing the material velocity in the reacting system in which reactions at several moving interfaces occur. All reactions lead to the lattice shift due to the difference of intrinsic diffusivities and different molar volumes. The following peculiarities are taken into account: (1) the deviation from local equilibrium at all interfaces; (2) the mobilities of the components in the bulk and interphase zone; and (3) the molar volumes of the components. We show the kinetic of the reactions, the non parabolic regime, the multiphase scale growth and present the practical application of the method. [ABSTRACT FROM AUTHOR]

In this paper the Diffusion Path (DP) method is presented. The method allows for the determination of the diffusion path during a reactive diffusion process. The initial conditions of the method are the phase diagram, diffusion coefficients in the phases and initial composition of the diffusion couple. The method allows for the determination of the diffusion path—the intermetallic phases generated during the diffusion process and the order of their generation. The results of the DP method are compared with the experimental results obtained for the Ti-NiCu diffusion couples with various Ni to Cu content ratio. [ABSTRACT FROM AUTHOR]

In this paper the vacancies formation and agglomeration under centrifugal force — sedimentation will be analyzed. The evolutionary algorithm for diffusion and vacancy evolution will be shown. The model predicts the location of vacancies agglomeration during the sedimentation process — the most probably place of voids formation. The computed results will be compared with experiments in Cu–brass diffusion couple. The influence of the centrifugal force on the vacancies migration will be presented. [ABSTRACT FROM AUTHOR]

In this paper the interdiffusion process and Frenkel effect (Kirkendall porosity) are studied in Ni-Cu and NiAl-Cu systems at 1273 K. The generalized Boltzmann-Matano method is used for calculation of the intrinsic diffusion coefficients as a polynomial function in the whole composition range. The calculated interdiffusion coefficient in Cu-Ni diffusion couple decrease with increasing Ni content. The total decrease of interdiffusion coefficient exceeds two orders of magnitude. The equation for the void growth rate is obtained. The experimental results of diffusion and voids formation are analyzed. The voids radii is estimated and compared with experiments. [ABSTRACT FROM AUTHOR]

In this paper the reactive diffusion in Ti–Ni–Al system is discussed at 1173 K. The calculation method based on the binary approach is presented. The key kinetic parameter is Wagner integral diffusion coefficient. The experimental and simulation results of reactive diffusion between pure Ti and β -NiAl are compared at 1173 K after 100 h. [ABSTRACT FROM AUTHOR]

The complete understanding of the phenomenological process related to the position of the Matano and Kirkendall plane in multicomponent system is still lacking. In this paper some aspects of Matano and lattice plane migration are studied by means of numerical simulations. New approach to calculate intrinsic diffusion coefficients in binary Ni–Au system and ternary Cu–Fe–Ni and Co–Fe–Ni is presented. Diffusivities were calculated using modified Boltzmann–Matano method. Self diffusion coefficients of the elements in diffusion couple must be known as well as position of the Kirkendall plane after the experiment to use this method. Diffusion profile was calculated using presented equations. Calculations compared with experimental data prove validity of the presented approach. This work proves that intrinsic diffusion coefficients should be given by the concentration function, not the exact value. [ABSTRACT FROM AUTHOR]

The Poisson equation is used to calculate the drift velocity in the two-dimensional diffusion couple. This approach is based on the bi-velocity (Darken) method which combines the Darken and Brenner concepts that the volume velocity is essential in defining the local material velocity in multicomponent mixture at non-equilibrium. As an example the arbitrary binary system is considered. It is shown that (1) the two dimensional calculations should be applied with the stochastization method and (2) the drift term in mass conservation law does not affect the calculations. [ABSTRACT FROM AUTHOR]

The two-dimensional approach for inter-diffusion and voids generation is presented. The voids evolution and growth is discussed. This approach is based on the bi-velocity (Darken) method which combines the Darken and Brenner concepts that the volume velocity is essential in defining the local material velocity in multi-component mixture at non-equilibrium. The model is formulated for arbitrary multi-component two-dimensional systems. It is shown that the voids growth is due to the drift velocity and vacancy migration. The radius of the void can be easily estimated. The distributions of (1) components, (2) vacancy and (3) voids radius over the distance is presented. [ABSTRACT FROM AUTHOR]

Abstract: In this work the competition between Kirkendall effect caused by intrinsic diffusion coefficients and vacancy generation and evolution is discussed. The proposed approach is based on the bi-velocity (Darken) approach which combines the Darken and Brenner concepts that the volume velocity is essential in defining the local material velocity at non-equilibrium. The model is formulated for arbitrary systems however for discussion only the binary system is presented. The distributions of (1) components, (2) vacancy and (3) voids radius over the distance are presented. [Copyright &y& Elsevier]

The solid-state diffusion in binary and ternary systems is overall treated and modeled using the bi-velocity method. The mathematical formulation is given, and the boundary conditions discussed. The model allows the calculation of concentration profiles, spatial distribution of the entropy production rate, and diffusion path. The last two can be used to identify the phases present in the diffusion zone of the ternary system, and determine the thicknesses of the respective layers. The model is applied for the first time to simulate diffusion during aluminization of nickel and its super-alloys, MAR-M200+Hf and CMSX-4, and the predictions are compared with the results of the experiments performed by the authors. The results give a new quantitative explanation of the high-active and low-active regimes of aluminization. It is, in particular, confirmed that the high-active and low-active regimes of nickel aluminization can be carried out by a variation of the HCl/H2 flow ratio. The most important, and a brand new, result concerns the entropy production rate. It is shown that its maxima coincidence with the two-phase zone boundaries in real space, which gives new insight into the modeling of the diffusion in ternary systems. [ABSTRACT FROM AUTHOR]

This paper concerns interdiffusion in a diffusion couple and determination of the Kirkendall plane. The “entropy density” model is proposed in which the entropy is used to predict the position of the Kirkendall plane in a multicomponent system. It is shown that the marker position depends on the drift velocity and pressure field only. Application of the model is presented for ternary CoFeNi diffusion couples of three various initial compositions. The concentration profiles and entropy densities are calculated for each diffusion couple. The positions of the Kirkenadl planes are determined and compared with those obtained by velocity-curve and trajectory methods. [ABSTRACT FROM AUTHOR]

Abstract: The phenomenological Boltzmann–Matano (B–M) analysis allows approximating the concentration dependent interdiffusion coefficients related to infinite binary diffusion couple experiments. However, the complete understanding of the phenomenological process related to the Kirkendall plane position coupled with the B–M method is still lacking. A purpose of the present study is to generalize the Boltzmann–Matano analysis and propose a method of estimating the unique intrinsic diffusion coefficients of components from the experimental concentration profile and the positions of Matano and Kirkendall planes in multicomponent systems. The proposed physico-chemical approach is used to approximate the intrinsic diffusivities in a single phase of Ni–Pd binary and Cu–Fe–Ni ternary diffusion couples. [Copyright &y& Elsevier]

A bi?velocity method is used to simulate the element?concentration evolution in the diffusion zone during the aluminization of a Rene?80 nickel?based superalloy. The basis of the method and the detailed calculations are presented. The model enables the prediction of the formation of intermetallic phases and multi?phase layers. The entropy?production rate can also be calculated, and it is shown that it might serve as a basis to indicate the interphases. The proposed model is applied to model the diffusion in a ternary Al?Cr?Ni system. The results of the calculations are compared with experimental element?concentration profiles, measured for the Rene?80 alloy subjected to aluminization by CVD. [ABSTRACT FROM AUTHOR]

Abstract: The understanding of the phenomenological process related to the position of the Kirkendall plane is still lacking. In this study some aspects of Kirkendall and lattice plane migration in binary diffusion couples are studied by means of numerical simulations by the bi-velocity method. The simulations are performed using constant and composition dependent intrinsic diffusion coefficients. The results show that the position and stability of the Kirkendall plane as well as a number of other interesting features can be predicted using the entropy–density curve calculated by the bi-velocity method. [Copyright &y& Elsevier]

Bi-velocity (Darken) method, which includes material drift and diffusion fluxes, is for the first time applied to describe mass transport in multiphase materials. The respective model is formulated in details and then applied for a ternary diffusion couple in which a two-phase zone can grow during isothermal diffusion. Thanks to the use of a phase-field order parameter, identified here with volume fraction of a chosen phase, the mass transport throughout both phases within a two-phase zone can be considered. The model allows smooth crossing of the type 1 boundary, which makes the mass transport equations valid in both single- and two-phase regions. The solution obtained for 1D geometry provides: (1) a diffusion path in the concentration triangle, (2) element-concentration profiles, (3) volume fractions of the phases in the two-phase zone and (4) drift-velocity distribution along x axis parallel to the mass transport. As an example, the interdiffusion in thediffusion couple of Type 0 boundary is modelled. The zigzag diffusion path is predicted and the profiles of the element concentrations are simulated. For the first time, the drift velocity for the diffusion in two-phase system is determined and correlated with the changes in volume fractions of the phases. [ABSTRACT FROM AUTHOR]

Abstract: The Bi-velocity Phase Field Method (BPFM), which allows a quantitative description of diffusion mass transport in multi-phase materials, is presented and applied to simulate formation of a diffusion zone in aluminized MAR-247. The method links the bi-velocity Darken approach with the phase-field model in which the diffusion zone is quantitatively characterized by phase volume fractions. Accordingly, composition dependent diffusivities in a two-phase region are defined. The present method allows calculation of element-distribution profiles and volume fractions of the phases across a diffusion couple. Hence, a diffusion path can be determined for three component systems and, besides, the average stress field and entropy production during diffusion can be calculated. An example of the application of BPFM in the modeling of high-temperature reactive diffusion in an AlCrNi ternary system is presented. The simulated results are compared with experimental data obtained in aluminization of MAR-247 by the chemical vapor deposition process. [Copyright &y& Elsevier]

Abstract: An approach to the problem of interdiffusion in multicomponent–multiphase system is presented. It couples bi-velocity (Darken) method, in which the mass conservation and volume continuity laws are considered, with the phase field model and is a generalization of the model based on the diffusion equation implemented in Dictra. The proposed bi-velocity phase field method allows computing the kinetics of the process, diffusive mass transport in every phase, concentration profiles, diffusion paths, and Kirkendall effect. The example problem presented here is a fundamental problem concerning the reactive diffusion at high temperatures in Al–Cr–Ni ternary system. It is a starting point that will allow modeling the coating composition to reduce interdiffusion and stabilize a desired microstructure, i.e., to extend coating life time. [Copyright &y& Elsevier]

In this work we solve the problem of the simultaneous growth and competition of intermediate phases. The crystal lattice as the frame of reference for diffusion is defined, based on the volume continuity equation. It permits the computation of the material velocity in a system in which reactions at several moving interfaces occur. All reactions lead to the lattice shift due to the difference of diffusivities and molar volumes. We simulate the CVD process followed by annealing in a non-oxidizing atmosphere. The computed kinetics and concentration profiles are compared with experimental results. [ABSTRACT FROM AUTHOR]

In the paper the mathematical model describing the gravity induced sedimentation process in multicomponent system is presented. The model is based on the generalized interdiffusion method (bi-velocity method): (1) the volume continuity equation, (2) equation of motion, (3) Cauchy stress tensor and (4) Nernst Planck flux formulae. The method is applied to simulate the sedimentation processes of the selenium isotopes and the ternary InSbGe system. [ABSTRACT FROM AUTHOR]

Abstract: The bi-velocity method allows quantitative description of the complex diffusion mass transport process for an unlimited number of elements. The method deals with (1) composition dependent diffusivities, (2) different partial molar volumes of components, (3) the stress field during the diffusion process and (4) entropy production. It allows for calculation of the time evolution of the components’ concentration profiles for non-ideal systems when thermodynamic activity data is available. Applications of the model describing interdiffusion in a ternary Cu–Fe–Ni system under the stress field is presented. [Copyright &y& Elsevier]

A theory of stress and elastic deformation during interdiffusion is presented. It is shown that it is consistent with the general Darken analysis and linear irreversible thermodynamics. Special consideration is given to local entropy production. An expression is derived for the rate of entropy production during interdiffusion and practical computations presented of the internal energy and entropy densities and the entropy production. It is shown that the entropy produced by the diffusion of mass is positive, [image omitted], and it does not depend on the frame of reference. The results span the gap between the Darken method, linear irreversible thermodynamics and treatments by Larche, Cahn and Stephenson. [ABSTRACT FROM AUTHOR]

Abstract: The bi-velocity concept of separation of diffusion and drift flows allows one to combine the convection and dissipative contributions to the mass and energy fluxes. It is shown that the bi-velocity method combined with statements of the first law of thermodynamics and the Euler’s and Liouville theorems is consistent with linear irreversible thermodynamics. We apply the derived formalism in modeling the two-dimensional sedimentation between Bi and Sb and demonstrate the satisfactory agreement with experimental data. The method allows modeling the sedimentation of isotopes in solids. [Copyright &y& Elsevier]

Abstract: A thermodynamically consistent framework is developed to combine the convection and dissipative contributions with the mass and energy fluxes in multicomponent materials. The method, which is known as bi-velocity or Darken method, is based on the postulate of the unique (independent on the frame of reference) transport of the mass due to diffusion. In this work we merge: (i) the combined statements of the first and second laws of thermodynamics (linear irreversible thermodynamics) and (ii) the Euler and Liouville theorems. We derive an expression for the rate of the entropy production that does not depend on the frame of reference and is always positive. We show that the derived set of partial differential equations describing the mechanochemical mass transport is thermodynamically consistent and can be used in advanced modeling. [ABSTRACT FROM AUTHOR]

In this paper, the morphology evolution in a Bi–Sb system under the centrifugal force at room temperature is discussed. The rotation speed was 35,000 rotations per minute and the length of the arm (radii) was 88 mm. It is shown, that after the centrifugation the phases become oriented in the direction parallel to the direction of the centrifugal force. Moreover, the voids move in the direction opposite to the centrifugal force direction. The movements of such voids result in their coalescence and finally lead to formation of cracks at the interface between ordered and disordered part of the sample. [ABSTRACT FROM AUTHOR]

In the present work surface roughness of copper samples after mechanical surface preparation processes (polishing, grinding, sand-blasting) and after exposure in non-oxidizing (high purity argon) and oxidizing (air) conditions at 700 and 750 °C have been evaluated by contact profilometer and by fractal analysis. Quantitative description of surfaces that are hidden from the sight of conventional methods is possible by fractal analysis, e.g. in the present work, the roughness of Cu 2 O/Cu boundary has been evaluated under oxide layer. It has been pointed out, that in both oxidizing and non-oxidizing conditions initial surface roughness of copper is affected by annealing at high temperature: at 700 °C surface roughness of polished and ground samples increased but at 750 °C decreased in comparison to surface roughness prior to heat treatment. For sand-blasted samples in both oxidizing and non-oxidizing conditions the lowest values of surface roughness parameters were obtained at 750 °C. It is then concluded that two phenomena are responsible for such effect: chemical reaction between copper and oxygen and surface diffusion of copper due to high temperature of annealing. Unlabelled Image • Surface of copper samples had been polished, ground and sand-blasted. • Surface roughness had been evaluated by contact profilometer and fractal analysis. • There are differences in roughness after annealing in oxidizing and non-oxidizing conditions at different temperatures. • Changes in roughness are caused by chemical reaction between Cu and O and surface diffusion of Cu at high temperature. [ABSTRACT FROM AUTHOR]

The experimental concentration profile in Ti-NiAl diffusion couple after diffusion at 1173 K for 100 h. Determination of diffusion coefficients in a ternary multiphase system is discussed as the data on the approximation method allowing to determine the diffusion coefficients in such systems are currently missing in the literature. In the present work, the mass conservation approach (MCA) for calculation the diffusivities in individual phases with the linear differences in composition is proposed. The diffusion data can be determined exclusively based on the experimental results. The method is implemented and validated for the ternary Ti-NiAl system, in which three intermetallic phases are stable. [ABSTRACT FROM AUTHOR]

Fe-based alloys are commonly used in almost every sector of human life. For different reasons, the surfaces of the real parts are prepared using different methods, e.g., mirror-like polishing, grit-blasting, etc. The purpose of the present work is to answer the question how the surface preparation influences the oxidation behavior of Fe-based alloys. To answer this question, a high-purity model alloy, Fe–5 wt%Al, was isothermally oxidized in a thermogravimetrical furnace. The post-exposure analysis included SEM/EDS (WDS) and XRD. The surface roughness was determined by a contact and laser profilometer. The obtained results demonstrate that the mechanical surface preparation influences oxidation kinetics as well as the microstructure of the oxide scale formed on the alloy at both studied temperatures. Namely, polishing and grinding caused local formation of Fe-rich nodules and sub-layer of protective Al2O3. In contrast, grit-blasting leads to the formation of a thick outer Fe-oxide and internal aluminum nitridation. A significant increase in the oxidation rate of the material after grit-blasting was attributed to grain refinement in the near-surface region, resulting in an increase in easy diffusion paths, namely grain boundaries. [ABSTRACT FROM AUTHOR]

Highlights • Surface roughness had been evaluated by contact profilometer and fractal analysis. • Influence of surface preparation on oxidation kinetic for pure Ni, Cu and Ni-Cu alloy. • Sand-blasting process improves surface roughness and contaminates surface with Al 2 O 3. • Surface preparation process promotes different diffusion mechanisms for pure Cu. Abstract In the present paper, the analysis of polishing, grinding and sand-blasting processes on oxidation behavior of nickel, copper and Ni30Cu70 alloy has been performed for three different temperatures. Surface roughness has been analyzed using two methods: contact profilometer and fractal analysis. It has been proved that R a parameter for sand-blasted samples is greater about one order of magnitude from ground and two order of magnitude from polished samples. Obtained mass gain plots after isothermal oxidation tests, SEM microphotographs and SEM/EDS analysis of the samples prove that morphology of the polished and ground samples does not vary significantly after oxidation at investigated temperatures, but differences in oxide layer thicknesses and mass gains were observed. Oxidized sand-blasted samples revealed that increased surface roughness and alumina intrusions remained in the surface after sand-blasting process change the oxidation process–mixed Al/(Ni, Cu or Ni-Cu) oxide is formed and separate Al 2 O 3 particles are visible. Moreover, differences in thickness ratio of copper oxides: Cu 2 O to CuO on copper samples oxidized at 750 °C (26, 20; 29, 64; 43, 45 for polished, ground and sand-blasted samples, respectively) prove that surface preparation influence high-temperature oxidation of the samples by promoting new diffusion mechanism. [ABSTRACT FROM AUTHOR]

In this work, the influence of three different surface preparation processes, namely polishing, grinding and sand-blasting on oxidation process of high purity Ni48Fe52 alloy (in at. %) at high temperature has been investigated. Surface roughness of differently treated samples was measured by contact profilometer. Isothermal oxidation was performed in thermogravimetric furnace at 900°, 950° and 1000 °C for 24 h in air. Cross-sections were prepared and then observed and analyzed by SEM (Scanning Electron Microscope) /EDS (Energy Dispersive Spectroscopy). It was determined that sand-blasting increases the number of dislocations and grain boundaries in the near-surface region and therefore slows down oxidation process by faster formation of mixed nickel/iron oxide that constitutes a barrier for outward iron diffusion. Internally oxidized zone is also more uniform and thicker for polished and ground samples in comparison to sand-blasted ones as a result of recrystallization of the latter and longer duration of faster oxygen solubility in the polished and ground samples. Unlabelled Image • Surface of Ni48Fe52 alloy samples were polished, ground and sand-blasted. • Surface roughness was measured by contact profilometer. • Internal FeO precipitates are fine for polished and ground samples. • Internal FeO precipitates along grain boundaries are coarse for sand-blasted samples. • Sand-blasting prior to oxidation slows down the oxidation process. [ABSTRACT FROM AUTHOR]

In the present work, Pyrowear53 steel was subjected to the impulse carburizing LPC process. After carburation, the material was quenched and tempered. Postprocessing analyses included the measurement of hardness, carbon content, residual austenite, and residual stresses. The results revealed that the thermochemical treatment resulted in the formation of an approximately 1200 µm wide carburized layer. The results of hardness, carbon content, and residual austenite measurement showed a continuous gradient (drop) in the measured values within the carburized layer. However, the results of residual stresses revealed the existence of a local extremum, namely, a zone with higher compressive stresses at the depth between 600 and 1000 µm. This was explained by a different temperature for initiation of martensite transformation as a function of carbon content. This difference resulted in the occurrence of two martensite expansion fronts at two different depths, resulting in an increase in compressive stresses at the noted depth range. Moreover, it was concluded that this region was present for material containing between 0.8 and 0.4 wt% carbon for Pyrowear53. [ABSTRACT FROM AUTHOR]

The interdiffusion in Ti-Ni70Cu30 diffusion couple was studied at 850 °C at times varied between 10 and 300 min. The diffusion paths for the samples were determined and the order of intermetallic phases occurring in the diffusion zone was established. It was concluded that after 10 and 30 min of diffusion annealing, four intermetallic phases formed, namely: Ti 2 Ni, TiNi, τ 1 and TiNi 3. Between 30 and 60 min, also the Ti 2 Cu phase appeared next to Ti 2 Ni phase forming the multi-zone region, which thickness almost doubled between 60 and 300 min of diffusion annealing at 850 °C. The formation of Ti 2 Cu and the multi-zone region was explained by the enrichment of Cu at the Ti 2 Ni/Ti boundary and connected with the increase in its diffusion flux. • Ti-Ni70Cu30 couple was annealed at 850 °C at times between 10 and 300 min. • after 10 and 30 min of annealing of Ti-Ni70Cu30 at 850 °C four phases formed. • between 30 and 60 min, the Ti 2 Cu appeared next to Ti 2 Ni forming two-phase region. • enrichment in Cu at the Ti 2 Ni/Ti boundary caused the formation of two-phase region. [ABSTRACT FROM AUTHOR]

• Sand-blasting causes formation of mixed Al/Fe oxide after oxidation of pure iron. • Increasing of surface roughness has greater impact on oxidation rate at 700 °C. • Multiscale analysis can be used in description of surface roughness prior oxidation. • Data for surface description may be derived by profilometer and by image analysis. • Gleason's method cannot be used in the characterization of curvature prior oxidation. In this paper, an investigation of the effect of surface roughness on oxidation of polished, ground and sand-blasted samples made of iron exposed at 700 and 750 °C for 2 h in air is reported. Surface roughness was described by the 2D data sets obtained by contact profilometer and derived from microphotographs taken at three different magnifications: 100×, 200× and 500×. Surface roughness and curvature were measured by means of conventional and multiscale analysis. Oxidation behavior was analyzed in terms of mass change and SEM/BSE (scanning electron microscopy/backscattered electrons) observations. The oxidation kinetics was found to be influenced by initial surface roughness, however, its effect was different at 700 °C and 750 °C as the contribution of surface diffusion is greater at the lower temperature. It was also concluded that multiscale analysis can be successfully applied in describing surface roughness prior to high-temperature oxidation processes. The most adequate results were obtained from the data derived by contact profilometer and from microphotographs taken at the highest magnification. [ABSTRACT FROM AUTHOR]

The influence of surface roughness on its high temperature oxidation for an Ni-base superalloy was studied using laser profilometry, atomic force microscopy, mass change measurements, glow-discharge optical emission spectrometry, scanning electron microscopy, X-ray diffraction, and positron annihilation methods. The isothermal and cyclic air oxidation tests were performed at 1000 °C and showed dependence of oxidation behavior on surface roughness. Smoother surfaces oxidation resulted in the formation of a multilayered oxide scale consisting of NiO, Cr2O3, and internally oxidized Al2O3 while a rougher surface formed protective Al2O3 scale. The factors responsible for different oxidation behaviors were determined as higher concentration of vacancies and increased residual stresses in the near-surface region of studied alloys. [ABSTRACT FROM AUTHOR]

In the present work the durability of the APS-TBC systems with bi-layer bond coat consisting of HTLA-CVD aluminide as bottom layer and APS-flashcoat of MCrAlY as upper layer was investigated. The additional factors potentially influencing TBC lifetime, namely substrate surface roughness prior to aluminizing and bond coat heat-treatment, were taken into account. The obtained results showed that the substrate surface roughness influences the IDZ morphology, however, IDZ disappears partly after heat-treatment and completely after high temperature exposure until the end of TBC life. The results of the lifetime measurement showed that the heat-treated TBC systems revealed up to three times longer lifetime (250 and 350 hot hours for systems with ground and grit-blasted substrate surface respectively) in comparison with non heat-treated ones (100 and 110 hot hours for systems with ground and grit-blasted substrate surface respectively). Moreover, TBC system with grit-blasted substrate revealed longer lifetime (350 hot hours) than system with ground substrate surface (250 hot hours). It was found that in both cases, the lifetime was limited by the Al-reservoir in the CVD layer and APS-flashcoat. The TBC failure was caused by the breakaway oxidation of depleted MCrAlY flashcoat particles that have led to the formation and propagation of cracks during cyclic exposure. Based on the results obtained in the present work, further elongation of the TBC lifetime is proposed by increasing of thickness of CVD aluminide layer. • Oxidation resistance of innovative APS-TBC systems with CVD aluminide and APS MCrAlY flashcoat • The effect of bondcoat heat-treatment on TBC life • The factors responsible for TBC life [ABSTRACT FROM AUTHOR]