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Failure and healing behavior of oxide scales for powder metallurgy superalloy with varying Nb contents (0, 0.5, 1, 2 wt%) during cyclic oxidation were studied. The cyclic oxidation test of four alloys was conducted using the discontinuous thermogravimetric method which consists of 100 cycles of 1 h exposure in air from 20 °C to 900 °C. The oxide scales after cyclic oxidation were systematically characterized by scanning electron microscope (SEM), laser scanning microscopy (LSM) etc. It has been found that the spallation of oxide scale in all alloys took place via expanding of the initiated cracks at grain boundaries into grain matrix. After spallation, the exposed alloy matrix would be re-oxidized into a Cr 2 O 3 layer to recover the failed oxide scales. The spallation tendency of oxide scale was significantly inhibited by Nb addition. This can be ascribed to the faster regeneration of Cr 2 O 3 layer in alloy with higher Nb content. • Nb addition significantly decreased the spallation of oxide scales. • The spallation in oxide scales starts in terms of cracks near grain boundaries. • The repetitive regeneration of Cr 2 O 3 of high-Nb alloy resulted in a smaller spallation area of the oxide scales. [ABSTRACT FROM AUTHOR]

Static recrystallization (SRX) behavior of Co-29Cr-6Mo-0.16 N (CCMN) alloy subjected to a prior compression to 30% at room temperature and a subsequent annealing at 1000 °C was ex-situ observed by using an electron backscatter diffraction (EBSD). Ascribed to the large negative stacking fault energy of the alloy at room temperature, it was found that the microstructure of alloy compressed at room temperature is characterized by plenty of intersected strain-induced martensitic transformation (SIMT) ε phase bands with a mean interval of 2–3 μm, which divided the parent grains into fine pieces surrounded by high angle boundaries (HABs). The static recrystallization of CCMN alloy in the subsequent annealing at 1000 °C takes place in terms of transient transition of the HABs into Σ3n boundaries and reorientation of new grains. • Recrystallization (RX) of CCMN alloy was ex-situ investigated by EBSD; • Alloy was subjected to room temperature compression and annealing at 1000 °C; • Compressed microstructure is characterized by intersected SIMT bands; • These bands divided the parent grains into fine pieces surrounded by HABs; • RX takes place in terms of transition of HABs into Σ3n boundaries; • RX of CCMN alloy is different from its DRX at same temperature; • This is ascribed to the large difference of SFE between two temperatures. [ABSTRACT FROM AUTHOR]

The Portevin-Le Châtelier (PLC) effect in a powder metallurgy (PM) Co-Ni-based superalloy was systematically investigated via the tensile tests at temperatures ranging from 200 to 600 °C and strain rates at 1.0 × 10−4 to 1.0 × 10−2. Both normal and inverse PLC effects were observed in the PLC regime, and the former appeared in the A and B types at a low temperature, whilst the latter appeared in the C type at an elevated temperature. Both positive and negative strain rate sensitivities (SRS) were shown in PLC regime, and SRS should be derived from same types of serrations. Based on the calculated activation energy, the substitutional atom Mo is considered to take primary responsibility for the PLC effect in present alloy. [ABSTRACT FROM AUTHOR]

In this study, the ball-on-disk sliding wear and tribocorrosion behavior in the H2SO4 and HCl solution of NiCoCrMoCu alloys with carbon additions of 0.2, 1, 1.5, and 2 wt.% with the Al2O3 ball as a counterpart was investigated systematically. Obvious tribocorrosion antagonistic effects were found after wear in both aqueous solutions. Compared with dry sliding wear conditions, the lubrication effect of the aqueous solution significantly reduces the wear rate of the alloy, and the reduction effect in the H2SO4 aqueous solution was more obvious than that in HCl. The antagonistic effects of the 0.2C and 1C alloys decrease with the load and sliding rate, while those of the 1.5C and 2C alloys increase. The (coefficient of friction) COF and wear rate under different loads and sliding rates were analyzed using the response surface analysis (RSM) method. It was found that the COF mainly showed dependence on the sliding rate, while the wear rate showed dependence on load and sliding speed. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of aging on twin boundary (TB) strengthening in magnesium alloys, the cyclic compressions along two orthogonal directions of samples with and without intermediate aging are carried out. The results show that the grains in all Mg alloys AZ31, AZ61 and AZ91 are significantly refined by twin boundaries (TBs). The TB strengthening is strongly dependent on both alloying element content and aging. Although grain refinement by TB formation occurs in AZ31, it exhibits slight strengthening effect even after aging. In contrast, significant TB strengthening after aging is observed in Mg alloys AZ61 and AZ91 with high contents of alloying elements. [ABSTRACT FROM AUTHOR]

Oxidation of a novel Ni-19Cr-17W-2Al-0.5Ti superalloy was investigated in air at 800–1100 °C. In spite of the local spallation of external oxide scale after prolonged oxidation at high temperature, the alloy maintains excellent oxidation resistance. The excellent oxidation resistance is related to continuous external Ti-rich oxide covering on Cr 2 O 3 scale, which inhibits, at least to a certain degree, the evaporation of Cr 2 O 3. In addition, this can also be ascribed to the fine Al 2 O 3 particles along grain boundaries of alloy matrix, which plays a key role in inhibiting the inward O diffusion and outward Cr diffusion through grain boundary. • Oxidation behavior of Ni-Cr-W-Al-Ti alloy was investigated. • Alloy remains good oxidation resistance upto 1100 °C. • The oxidation is dominated by Cr diffusion in Cr 2 O 3. • Ti-rich oxide inhibits the evaporation of Cr 2 O 3. • Al 2 O 3 in alloy matrix inhibits inward O diffusion and outward Cr diffusion. [ABSTRACT FROM AUTHOR]

Effect of Ti addition on oxidation behavior of Ni-Cr-W alloys was systematically investigated by isothermal oxidation in air. The oxidation rate is accelerated by Ti addition, due to that Cr 2 O 3 vacancy density is increased by Ti4+ occupies Cr3+ position, which promotes the formation of Cr 2 O 3 scales. Ti addition induced the formation of TiO 2 but inhibited the formation of Ni oxide. Ti segregated on the external Cr 2 O 3 scales after oxidation for a period time. Besides, internal oxidation and nitridation were found in both alloys containing Ti. The depth of internal oxidation and nitridation increases with the increase of Ti content. • Influence of Ti on oxidation of Ni-Cr-W alloy was investigated. • Ti accelerated the oxidation via enhancing Cr 2 O 3 forming. • Ti inhibited the formation of Ni oxide. • Ti accelerated the internal oxidation and internal nitridation. [ABSTRACT FROM AUTHOR]

A novel Co-Ni-based superalloy was manufactured by powder metallurgy (PM) process. The microstructure and mechanical properties of PM alloy were analyzed in detail and compared with the corresponding casting alloy. After cold swaging to 66% and subsequent aging for 800 °C for 3 h on solution treated (ST) PM alloy, the yield strengths of PM superalloy can be doubled and tripled to be 1500 and 2265 MPa respectively, as compared with 700 MPa of ST PM alloy. In contrast, for the same casting alloy after subjected to similar treatments, their corresponding yield strengths were 1100 and 1650 MPa, respectively, which are much lower than these of PM alloy. Strengthening mechanism of both PM and casting alloys were quantitatively calculated, unmasking that the higher mechanical property of PM alloy can be mainly ascribed to the higher contribution from grain boundary and precipitation strengthening. • A novel superalloy was manufactured by powder metallurgy (PM) process. • The microstructure and properties were compared with the casting alloy. • PM alloy demonstrates supior property than casting alloy. • Grain boundary and precipitation play higher strengthening contribution in PM alloy. [ABSTRACT FROM AUTHOR]

The effect of Mg/Ca/Nb/Ag alloying on the morphology and microstructure of powder metallurgy Cu10Fe alloy was investigated systemically in this work. Alloying of Ca reduces the size of Fe-rich particles, while alloying of Mg/Nb/Ag increases the Fe-rich particles. This is attributed to the different roles of various alloying elements on the liquid-phase separation behaviors as well as diffusion of Fe atoms during the solidification. Coarse size spherical Fe-rich particles with a face centered cubic structure are observed in Cu Fe alloys bearing Mg/Ag/Nb, whilst the alloying of Ca favors the formation of fine spherical Fe-rich particles with a body centered cubic structure. The factor governing the morphology is found to be interfacial energy for Cu Fe alloys containing Mg/Ag/Nb and elastic energy for Cu-Fe-Ca alloy, respectively. Coarse size Fe-rich particles are hard to deform during subsequent rolling, but the fine Fe-rich particles can co-deform with Cu matrix. This study could provide a detailed picture regarding the influence of various alloying element types on the size, morphology, and lattice structure of Fe phase of Cu Fe alloy. • The effect of Mg/Ca/Nb/Ag alloying on the morphology and microstructure of powder metallurgy Cu10Fe alloy was investigated. • Coarse size spherical Fe-rich particles with a FCC structure are observed in Cu Fe alloys bearing Mg/Ag/Nb. • Alloying of Ca favors the formation of fine spherical Fe-rich particles with a BCC structure. • The factor governing the morphology is interfacial energy for alloys containing Mg/Ag/Nb and elastic energy for Cu-Fe-Ca alloy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solvothermal treatment on flake Cu-Ag powder was performed. • Anti-oxidation performance of powder was investigated. • The treatment significantly enhanced the oxidation resistance of powder. • This was ascribed to the reaction between Cu matrix and sodium formate solution. • A [Cu(μ.HCOO)(OH) 2 ] 2 layer was generated on the surface of powders during treatment. Cu-Ag flake powders demonstrate strong potential applying as the conductive phase in conductive polymer composite due to the good combination properties of electrical conductivity and anti-oxidation performance. In this study, the influence of solvothermal treatment in sodium formate on the surface microstructure and anti-oxidation performance of flake Cu-Ag powder was investigated systematically. The results indicated that solvothermal treatment at 200℃ for at least 16 h significantly enhanced the oxidation resistance of the aged Cu-5Ag flake powder in air, which was ascribed to the reaction between Cu matrix and sodium formate solution to create a [Cu(μ.HCOO)(OH) 2 ] 2 layer on the surface of powders and precipitated Ag along GBs during aging treatment. During the oxidation process, the [Cu(μ.HCOO)(OH) 2 ] 2 formed on the surface of flake powders provided cathodic protection to Cu atoms, and the precipitated Ag along GBs blocked the diffusion channels of Cu and O atoms, which resulted in exceptionally high anti-oxidation performance up to 283℃ of Cu-Ag flake powders. [ABSTRACT FROM AUTHOR]

• Characteristics of various PREP powders were investigated by CT. • Higher powder fluidity at low rotation speed than high rotation speed. • Fraction of hollow particle is dependent on particle size. • Alloy type plays a key role on hollow particle fraction. Flowability, particle size distribution and particle inner pore features for powders of Ti-6Al-4V, 316-steel, and Co-29Cr-6Mo alloys produced by plasma rotating electrode process (PREP) at various rotation speeds are analyzed by using scanning electron microscopy (SEM) and synchrotron X-ray computed tomography (CT). The results show that powder flowability is related to particle size distribution, surface morphology and dynamic friction coefficient of the alloy itself. This results in the higher powder flowability at low rotation speed than that at high rotation speed. Average particle size is roughly proportional to the square root of the reciprocal of rotation speed. In addition, particle size has an important effect on the particle porosity and the number faction of hollow powder in coarse powder is obviously larger than that in fine powder. Meanwhile, the alloy composition also plays a key role on porosity due to the various surface tension of alloys. [ABSTRACT FROM AUTHOR]

Corrosion behaviours in hydrofluoric acid solution and mechanical performances of Ni-16Cr-11Mo-6Fe-2Cu and Ni-30Co-16Cr-11Mo-6Fe-2Cu alloys were investigated by using a variety of methods. No precipitate is observed in the present low Mo alloys, suggesting the excellent structural stability. Co leads to grain refinement and localized microstructure after hot rolling, resulting in significant enhancement in both hardness and tensile strength. Owing to the addition of Cu, all alloys with and without hot rolling show near weight loss rates after immersion. This is ascribed to the dominant passive film of Cu, which demonstrates the superior stability among the constitute elements of alloys. Image 1 • Low Mo Ni-based alloys show superior phase stability. • Co leads to enhanced strength by grain refinement and localized microstructure. • All alloys even after hot rolling show comparable weight losses after immersion. • The comparable corrosion resistance is related to dominant passive film by Cu. [ABSTRACT FROM AUTHOR]

Al-Sn alloy is utilized as a bearing material to replace conventional Sn-based alloy in the design of bearing liners due to its higher load-carrying capacity and wear resistance. However, cracks readily initiate in casting Al-Sn alloy near the coarse Sn phase, leading to low mechanical properties and insufficient wear resistance. The present study introduces a new method, additive friction stir deposition (AFSD), to produce AlSn20Cu alloy with fine grains and sub-micron-scale Sn phases, resulting in enhanced mechanical performance and wear resistance. Compared to both casting and cold rolling + annealing AlSn20Cu alloys, the ultimate tensile strength of AFSD AlSn20Cu alloy is improved by 80.56 % and 16.67 % respectively. Additionally, AFSD AlSn20Cu alloy demonstrates a lower coefficient of friction (COF) and lower wear rate without significant subsurface damage. This is attributed to the fine and uniformly distributed Sn phase forming a uniform and dense surface lubrication layer that adapts the friction pair to the boundary lubrication state, preventing the initiation and development of cracks. • AlSn20Cu alloy was produced by additive friction stir deposition (AFSD). • •The AFSD alloy is characterized by fine grains and sub-micron-scale Sn phases. •The AFSD alloy exhibits outstanding mechanical performance and wear resistance compared to both casting and cold rolling + annealing alloys. •This is attributed to the fine and uniformly distributed Sn phase in AFSD alloy. •The fine Sn phase prevented the initiation and development of cracks. [ABSTRACT FROM AUTHOR]

Y/Hf-doped AlCoCrFeNi high-entropy alloys stand out for their potential application in high temperature coatings. Thereinto, both Cr and Al are crucial for improving oxidation properties. However, simultaneously increasing the content of Al and Cr is not advisable, since it can significantly reduce the ductility/toughness of the coating. In this research, we proposed an equivalent replacement method of Al and Cr, namely, tuning Al/Cr ratio (ACR), to enhance the elevated-temperature oxidation resistance of AlCoCrFeNi alloys. This strategy was verified by the 1000 h/1100 °C oxidation tests of three Y-doped AlCoCrFeNi alloys with different ACRs of 0.78, 0.58 and 0.41. The test results indicated an elusive transformation of oxidation rate occurred on these alloys, that the alloy with lowest ACR exhibited an initially higher oxidation rate but a lower oxidation rate over an extended period, in comparison to those higher ACR alloys. The underlying oxidation mechanisms were uncovered using microscopic techniques and thermodynamics calculations. The initial higher oxidation rate was ascribed to the rapid growth of spinel oxides, while the extended slower oxidation process was attributed to the resulting Al 2 O 3 scale with larger grain sizes. Thermodynamic assessment revealed that larger Al 2 O 3 grains corresponding to fewer grain boundaries decreased the diffusion coefficient of oxygen in Al 2 O 3 scale. Our research is of both theoretical and industrial importance for clarifying the high temperature oxidation mechanism of Y-doped AlCoCrFeNi alloys and enhancing the oxidation resistance in multicomponent alloy systems. [Display omitted] • The rapid growth of spinel oxides contributes to the initially higher oxidation rate. • The growth of Al 2 O 3 layer governs the extended oxidation process. • Larger Al 2 O 3 grains are responsible for reducing the extended oxidation rate. [ABSTRACT FROM AUTHOR]

This study focuses on the effect of the main antioxidation element Al on the high-temperature oxidation resistance of Ni-Cr-Co based superalloys. A novel "3D printing-high temperature diffusion" high-throughput method was used to accurately determine the critical Al content to form continuous Al 2 O 3 film. Results show that Al 2 O 3 film significantly affects the element diffusion process during oxidation, and the critical Al content to form continuous Al 2 O 3 film is 0.8 wt%. This conclusion was further confirmed by the corresponding discrete samples. It was also found that Ni-Cr-Co based superalloys exhibit "oxidation weight loss" and "K p -antioxidation positive correlation" phenomena in high humidity condition. • A novel "3D printing-high temperature diffusion" high-throughput method was used. • The critical Al content to form continuous Al 2 O 3 film was precisely confirmed. • "Oxidation weight loss" caused by Cr and Mo oxides volatilization was studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag precipitation in particle surface is dependent on size at low temperature. • Ag precipitation was independent on particle size at high temperature. • Ag diffusion at low temperature is dominated by surface and GB diffusion. • Ag network in particle surface improve the oxidation resistance of powders. Ag precipitation and the resultant oxidation behavior of Cu-5wt.%Ag powder of various particle sizes were investigated. During low-temperature aging (250 ℃), Ag precipitation along grain boundaries (GBs) in particle surface is closely dependent on particle size. The depth of Ag precipitation-free area (Ag-PFA) are 0 μm, 1.17 μm and 2.78 μm for S, M and L samples, respectively. While for high-temperature aging (550 ℃), the Ag precipitation was independent on particle size. This is ascribed to that Ag diffusion in particles at low temperature is dominated by both surface diffusion and GB diffusion, while at the higher temperature, the volume diffusion also becomes dominant. The formation of a continuous 3D-Ag network along GBs in particle surface can significantly improve the oxidation resistance of powders. [ABSTRACT FROM AUTHOR]

• Influence of aging on oxidation of Cu-Ag alloy was investigated. • Aging enhanced the precipitation of Ag along grain boundaries. • Ag along grain boundaries is continuous. • Ag inhibited both the O inwards diffusion and Cu outwards diffusion. • Aging enhanced the oxidation of Cu-Ag alloy. Improving the oxidation resistance without sacrificing the electrical conductivity of Cu is of great importance for researchers due to its widespread application. In this study, oxidation resistance of Cu-5 wt%Ag alloy under solution treatment (ST) and aging treatment (AT) were studied systematically. It has been confirmed that AT sample demonstrates considerably higher oxidation resistance than ST sample at elevated temperatures. The aging treatment enhanced the formation of a continuous Ag network along grain boundaries, which could act as a barrier for both inward diffusion of oxygen and outward diffusion of Cu along grain boundaries during oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fast diffusion of Al causes the formation of β phase and increment of γ′ phase in substrate. • The Al-Cr interference effect is revealed, which causes the pile-up of Cr near the coating/superalloy interface. • Thermodynamics calculations verify that the γ′ depletion in substrate was ascribed to the loss of Ta and Ti. Metallic coatings are widely employed to improve the oxidation resistance of superalloys. However, the interdiffusion between the metallic coatings and the superalloys leads to microstructural degradation in both. Some of the underlying degradation mechanisms are still elusive, e.g., the γ′ (Ni 3 Al) phase depletion in superalloys, where a large amount of γ′ precipitates are dissolved in the γ matrix even though the incoming Al from coatings indeed increases the Al content. Here, we investigated the interdiffusion behavior between the Amdry365 coating and the IN792 superalloy at 1100 °C, using multiple microscopic techniques and thermodynamics calculations. Our results showed an excellent agreement between experiments and thermodynamics simulations, indicating the dominant role of Al on the initial diffusion-induced phase transitions. We proposed the Al-Cr interference effect to account for the pile-up behavior of Cr and the reduced Al content near the coating/superalloy interface. The local phase equilibrium calculations revealed that the γ′ depletion in the superalloy is primarily attributed to the loss of γ′-forming elements, such as Ta and Ti. Our findings opened up an avenue for studies on the superalloy/coating interdiffusion, contributing to reducing this damaging impact. [ABSTRACT FROM AUTHOR]

Microstructure and mechanical properties of novel Ni-20Co-12Cr superalloys, with and without Nb addition, were systematically studied during long-term thermal exposure. With increased exposure time, the average diameter of the γ′ precipitates increased in both alloys in succession; this is more obviously observed in alloy containing 1 wt% Nb (1Nb). It is suggested that Nb increased the γ′ coarsening rate by accelerating the diffusion of Al and Nb in γ matrix. In addition, the γ′ phase fraction is increased by about 4% in 1Nb compared to the alloy without Nb (0Nb). The morphology of the γ′ phase changed from near-spherical to cuboidal shape during exposure in both alloys. Due to the increased γ/γ′ lattice misfit by Nb addition, 1Nb alloy showed an earlier tendency of shape change. Vickers hardness results revealed that the overall hardness decreased with the exposure time because the size increment of the γ′ precipitate weakened the precipitates strengthening and Orowan strengthening. [ABSTRACT FROM AUTHOR]

The roles of Co on the strain-hardening behavior, deformation mechanism, mechanical properties and facture mode of Ni–16Cr–11Mo–2Cu alloy were thoroughly investigated using tensile tests, SEM, EBSD, TEM and HRTEM. Two alloys with a similar sole FCC-γ phase constitution, near grain size only except the composition difference of 30 wt% Co were fabricated in purpose. Co addition can overcome the strength-ductility trade-off by enhancing the strain-hardening rate and capacity. The deformation behavior evolves from slip-dominated to SFs-dominated after Co addition, due to significant decrease of stacking fault energy, the critical stresses for both SFs and twinning by Co addition. In terms of facture mode, dimples-dominated ductile fracture is transformed to quasi-cleavage fracture composed of cleavage planes and dimples after Co addition. This is probably owing to the special role of SFs on intensifying stress/strain incompatibility phenomenon in polycrystalline alloys. [ABSTRACT FROM AUTHOR]

Corrosion behavior and mechanical property of 5083 Al-Mg alloy manufactured by additive friction stir deposition (AFSD) were investigated compared with 5083-H112 alloy. AFSD is beneficial to reduce the pitting corrosion sensitivity of 5083 alloy due to refinement and re-dissolution of Mn rich secondary phase particles. But the intergranular corrosion (IGC) susceptibility of AFSD alloy is more significant due to the exfoliation of fine equiaxed grains after sensitization. This can be ascribed to that the grain boundaries of AFSD alloy after sensitization are dotted with β-phase which tends to be attacked by acid. [Display omitted] • 5083 Al alloy was manufactured by AFSD. • AFSD reduced the pitting corrosion of alloy. • Intergranular corrosion of AFSD alloy after sensitization is more significant. • AFSD alloy showed excellent mechanical property due to fine microstructure. [ABSTRACT FROM AUTHOR]

[Display omitted] • Flake Cu-5Ag powder was prepared by ball milling. • Aging is effective to enhance oxidation resistance of powder. • Ag precipitated along grain boundaries and in the interior of grains after aging. • Ag hindered the inward diffusion of O through the defects during oxidation. In this study, flake Cu-5Ag alloy powder with mean diameter-thickness ratio (D / T) higher than 110 were successively prepared by ball milling. Effect of milling time on the morphology and D / T of flake powder was investigated in detail. The subsequent aging treatment at 400 ℃ was proved to be effective in enhancing the oxidation resistance of flake Cu-5Ag powder. After oxidation at 300℃ for 10 min, the oxygen content in the surface of aged Cu-5Ag flake powder was reduced by approximately 50 % compared to the as-milled Cu-5Ag flake powder. The aging enhanced the precipitation of Ag phase along the grain boundaries and in the interior of grains, which could act as hindrances to the preferential inward diffusion of oxygen along the defects during oxidation. [ABSTRACT FROM AUTHOR]

• Strengthening from texture and dual-precipitates of Mg alloy is introduced. • Mg alloy by this method exhibits remarkable increase of yield strength. • Extension of this strengthening strategy to other HCP alloys are discussed. This work proposes a novel strengthening strategy for HCP alloy by fully utilizing the strengthening roles from texture and dual-precipitates in both basal and prismatic planes. The binary Mg-7Al (at%) alloy fabricated by such a strategy exhibits a superior combination of strength and strain hardening rate in major plastic strain ranges. Unlike conventionally fixed distribution of precipitate on given lattice plane, both basal and prismatic Mg 17 Al 12 precipitates are firstly engineered to co-exist and reinforce Mg alloy. Additionally, this work reports the presence of a new precipitate morphology with a hammer-like geometric configuration for the first time to date. Further application and extension of this novel strengthening strategy to other HCP alloys, like Ti, Zr, are also discussed. [ABSTRACT FROM AUTHOR]

This research was aimed at investigating the high temperature oxidation behavior of Inconel 718 superalloy fabricated by electron beam melting with the building direction of 0°, 55° and 90° deviation from the Z axis of cylindrical samples. Columnar γ-fcc phase with preferred crystal orientations was found in all specimens. With the temperature ranging from 700 to 1000 °C, the 0° sample, symbolized by the lowest grain boundary density, and largest grain size, reveals the best oxidation performance. It is concluded that the building direction has more impact on the amount of grain boundary density than crystal orientation, which determined the oxidation resistance. [ABSTRACT FROM AUTHOR]