Corrosion behavior of air plasma spraying zirconia-based thermal barrier coatings subject to Calcium–Magnesium–Aluminum-Silicate (CMAS) via burner rig test

Three different kinds of thermal barrier coatings (TBCs) — 8YSZ, 38YSZ and a dual-layered (DL) TBCs with pure Y₂O₃ on the top of 8YSZ were produced on nickel-based superalloy substrate by air plasma spraying (APS). The Calcium–Magnesium–Aluminum-Silicate (CMAS) corrosion resistance of these three kinds of coatings were researched via burner rig test at 1350 °C for different durations. The microstructures and phase compositions of the coatings were characterized by SEM, EDS and XRD. With the increase of Y content, TBCs exhibit better performance against CMAS corrosion. The corrosion resistance against CMAS of different TBCs in descending was 8YSZ + Y₂O₃, 38YSZ and 8YSZ, respectively. YSZ diffused from TBCs into the CMAS, and formed Y-lean ZrO₂ in TBCs because of the higher diffusion rate and solubility of Y³⁺ in CMAS than Zr⁴⁺. At the same time, 38YSZ/8YSZ + Y₂O₃ reacts with CAMS to form Ca₄Y₆(SiO₄)₆O/Y_4·67(SiO₄)₃O with dense structure, which can prevent further infiltration of CMAS. The failure of 8YSZ coatings occurred at the interface between the ceramic coating and the thermally grown oxide scale (TGO)/bond coating. During the burner rig test, the Y₂O₃ layer of the DL TBCs peeled off progressively and the 8YSZ layer exposed gradually. DL coatings keep roughly intact and did not meet the failure criteria after 3 h test. 38YSZ coating was partially ablated, the overall thickness of the coating is thinned simultaneously after 2 h. Therefore, 8YSZ + Y₂O₃ dual-layered coating is expected to be a CMAS corrosion-resistant TBC with practical properties.     

CMAS corrosion resistance in high temperature and rainwater environment of double-layer thermal barrier coatings odified by rare earth

In order to explore the difference of CMAS corrosion resistance in high temperature and rainwater environment of single-layer and double-layer thermal barrier coatings (TBCs), and further reveal the mechanism of CMAS corrosion resistance in above environment of double-layer TBCs modified by rare earth, two TBCs were prepared by air plasma spraying, whose ceramic coating were single-layer ZrO₂–Y₂O₃ (YSZ) and double-layer La₂Zr₂O₇(LZ)/YSZ, respectively. Subsequently, CMAS corrosion resistance tests at 1200 °C and rainwater environment of two TBCs were carried out. Results demonstrate that after high temperature CMAS corrosion for the same time, due to phase transformation, the volume of YSZ ceramic coating in single-layer TBCs shrank and surface cracks formed, which would lead to coating failure. When LZ ceramic coating of double-layer TBCs reacted with CMAS, compact apatite phases and fluorite phases formed, the penetration of CMAS into ceramic coating was inhibited effectively. Raman analysis and calculation results show that both of the surface residual stress of ceramic coating in two TBCs were compressive stress, and the residual stress of ceramic coating in double-layer TBCs were smaller than that of single-layer TBCs. Atomic force microscopy of TBCs after CMAS corrosion show that surface of double-layer TBCs was more uniform and compact than that of single-layer TBCs. The electrochemical properties in simulated rainwater of two TBCs after high temperature CMAS corrosion showed that double-layer TBCs possessed higher free corrosion potential, lower corrosion current and higher polarization resistance than those of single-layer TBCs. Consequently, the presence of LZ ceramic coating effectively improved CMAS corrosion resistance in high temperature and rainwater environment of double-layer TBCs.     

2ZrO2·Y2O3 Thermal Barrier Coatings Resistant to Degradation by Molten CMAS: Part I,Optical Basicity Considerations and Processing

The higher operating temperatures in gas‐turbine engines enabled by thermal barrier coatings (TBCs) engender new materials issues, viz silicate particles (sand, volcanic ash, fly ash) ingested by the engine melt on the hot TBC surfaces and form calcium–magnesium–alumino–silicate (CMAS) glass deposits. The molten CMAS glass degrades TBCs, leading to their premature failure. In this context, we have used the concept of optical basicity (OB) to provide a quantitative chemical basis for the screening of CMAS‐resistant TBC compositions, which could also be extended to environmental barrier coatings (EBCs). By applying OB difference considerations to various major TBC compositions and two types of important CMASs—desert sand and fly ash—the 2ZrO₂·Y₂O₃ solid solution (ss) TBC composition, with the potential for high CMAS‐resistance, is chosen for this study. Here, we also demonstrate the feasibility of processing of 2ZrO₂·Y₂O₃(ss) air‐plasma sprayed (APS) TBC using commercially developed powders. The resulting TBCs with typical APS microstructures are found to be single‐phase cubic fluorite, having a thermal conductivity <0.9 W·(m·K)^?1 at elevated temperatures. The accompanying Part II paper presents results from experiments and analyses of high‐temperature interactions between 2ZrO₂·Y₂O₃(ss) APS TBC and the two types of CMASs.     

YAG:Ce3+ piezo-spectroscopy: A high-sensitive method used for stress characterization of thermal barrier coating

The internal residual stress of thermal barrier coating (TBC) induced during the preparation and service process is the kernel cause of internal and interfacial failure and even the structure damage and destruction. Therefore, the accurate characterization of the internal stress is of great significance for TBC property and life evaluation. Fluorescence piezo-spectroscopic technology has been used to realize the nondestructive measurement of the TBC internal stress. However, the sensitivity of the existing Eu³⁺/Cr³⁺ fluorescence, namely, the piezo-spectroscopic coefficient, is normally <10 cm⁻¹/GPa. There is still an urgent need to develop a sensitive method or material of piezo-spectroscopy for the precision measurement of the TBC internal stress. This paper used Ce³⁺ as a sensing medium to detect stress. YAG:Ce³⁺ was applied as the top-coating material of TBC. Then, calibration experiments of the piezo-spectroscopic coefficient were carried out. The results demonstrated that the obtained Ce³⁺ piezo-spectroscopic coefficient can be up to 4.48 cm⁻¹/MPa, almost three magnitudes larger than other existing fluorescence piezo-spectroscopic technologies.     

Corrosion resistance and thermal-mechanical properties of ceramic pellets to molten calcium-magnesium-alumina-silicate (CMAS)

Because gas turbine engines must operate under increasingly harsh conditions, the degradation of thermal barrier coatings (TBCs) by calcium-magnesium-alumina-silicate (CMAS) is becoming an urgent issue. Mullite (3Al₂O₃·2SiO₂) is considered a potential material for CMAS resistance; however, the performance of mullite in the presence of CMAS is still unclear. In this study, mullite and Al₂O₃–SiO₂ were premixed with yttria stabilized zirconia (YSZ) in different proportions, respectively. Porous ceramic pellets were used to conduct CMAS hot corrosion tests, and the penetration of molten CMAS and its mechanism were investigated. The thermal and mechanical properties of the samples were also characterized. It was found that the introduction of mullite and Al₂O₃–SiO₂ mitigated the penetration of molten CMAS into the pellets owing to the formation of anorthite, especially at 45 wt% mullite/55 wt% YSZ. Compared with Al₂O₃–SiO₂, mullite possesses a higher chemical activity and undergoes a faster reaction with CMAS, thus forming a sealing layer in a short time. Additionally, the thermal expansion coefficient, thermal conductivity, and fracture toughness of different samples were considered to guide the architectural design. Considering the CMAS corrosion resistance, thermal and mechanical performance of TBCs systematically, a TBC system with a multilayer architecture is proposed to provide a theoretical and practical basis for the design and optimization of the TBC microstructure.     

Crystal structure,energy transfer mechanism and tunable luminescence in Ce3+/Dy3+ co-activated Ca20Mg3Al26Si3O68 nanophosphors

Ce³⁺, Dy³⁺ and Ce³⁺/Dy³⁺ co-doped Ca₂₀Mg₃Al₂₆Si₃O₆₈ (CMAS) nanophosphors were synthesized via modified solution-combustion method. Sharp X-ray diffraction patterns confirmed the formation of pure crystalline phase of Ca₂₀Al₂₆Mg₃Si₃O₆₈ as an orthorhombic crystal system having space group Pmmn. The phase purity of as synthesized material has allowed reliable structural parameters to be obtained from the Rietveld analysis of its powder diffraction pattern. The Ce³⁺, Dy³⁺ and Ce³⁺/Dy³⁺ emission at different lattice sites in CMAS host has been identified and discussed. Under ultra-violet (UV) excitation, optical properties and the energy transfer mechanism from Ce³⁺ to Dy³⁺ in CMAS: Ce³⁺/Dy³⁺ nanophosphors have been elaborated by photoluminescence spectroscopy. Also, the effects of doping and sintering temperature on the structure of prepared CMAS host samples have been investigated in detail. The Ce³⁺/Dy³⁺ concentration quenching mechanism due to multipole–multipole interaction has been studied and the critical energy-transfer distance was calculated to be 7.8 Å. The band gap of the synthesized phosphors was calculated from diffuse reflectance spectra using the Kubelka–Munk function. A uniform layered structure network has been revealed in scanning electron microscopy images of the CMAS phosphor. Transmission electron microscopy results indicate nanocrystalline nature of synthesized phosphors. CMAS: 1 m% Ce³⁺ and CMAS: 0.5 m% Dy³⁺ nano-luminescent powders are promising candidate as a blue and blue–yellow emitting UV convertible phosphor for application in white light emitting diodes. By utilizing the energy transfer mechanism in present CMAS: Ce³⁺/Dy³⁺ nanophosphors, with an appropriate tuning of the activator content, these phosphors can exhibit great potential for white light emission, as single-emitting component phosphors in solid state lighting technology.     

Thermal cycling performances of multilayered yttria-stabilized zirconia/gadolinium zirconate thermal barrier coatings

Gadolinium zirconate (Gd₂Zr₂O₇, GZO) as an advanced thermal barrier coating (TBC) material, has lower thermal conductivity, better phase stability, sintering resistance, and calcium-magnesium-alumino-silicates (CMAS) attack resistance than yttria-stabilized zirconia (YSZ, 6-8 wt%) at temperatures above 1200°C. However, the drawbacks of GZO, such as the low fracture toughness and the formation of deleterious interphases with thermally grown alumina have to be considered for the application as TBC. Using atmospheric plasma spraying (APS) and suspension plasma spraying (SPS), double-layered YSZ/GZO TBCs, and triple-layered YSZ/GZO TBCs were manufactured. In thermal cycling tests, both multilayered TBCs showed a significant longer lifetime than conventional single-layered APS YSZ TBCs. The failure mechanism of TBCs in thermal cycling test was investigated. In addition, the CMAS attack resistance of both TBCs was also investigated in a modified burner rig facility. The triple-layered TBCs had an extremely long lifetime under CMAS attack. The failure mechanism of TBCs under CMAS attack and the CMAS infiltration mechanism were investigated and discussed.     

2ZrO2·Y2O3 Thermal Barrier Coatings Resistant to Degradation by Molten CMAS: Part II,Interactions with Sand and Fly Ash

Based on the application of OB considerations (Part I) to various major thermal barrier coating (TBC) compositions and two types of important calcium–magnesium–alumino–silicates (CMAS)—desert sand and fly ash—the 2ZrO₂·Y₂O₃ solid solution (ss) TBC composition, with high CMAS‐resistance potential, is chosen for studying molten‐CMAS/TBC interactions. It is demonstrated that 2ZrO₂·Y₂O₃(ss) air plasma sprayed (APS) TBCs are highly resistant to high‐temperature attack by both sand‐CMAS and fly‐ash‐CMAS. Despite the differences in the compositions of the two CMASs, the overall CMAS‐attack mitigation mechanisms in both cases appear to be similar, viz reaction between 2ZrO₂·Y₂O₃(ss) APS TBC and the CMAS, and the formation of main reaction products of Y‐depleted c‐ZrO₂ and nonstoichiometric Ca–Y apatite. Large differences in the OBs (ΔΛ) between the 2ZrO₂·Y₂O₃(ss) and the CMASs are good predictors of ready reaction between this TBC and these CMASs. While the details of the CMAS‐mitigation mechanisms can depend critically on various other aspects, the OB difference (ΔΛ) calculations could be used for the initial screening of CMAS‐resistant TBC compositions.     

Equimolar YO1.5 and TaO2.5 co-doped ZrO2 as a potential CMAS-resistant material for thermal barrier coatings

Calcium-magnesium-alumino-silicates (CMAS) corrosion in thermal barrier coatings (TBCs) is becoming more serious with increasing operation temperature of turbine engines. Here, we report an equimolar YO_1.5 and TaO_2.5 co-doped ZrO₂ (Zr_0.66Y_0.17Ta_0.17O₂, ZYTO) as a potential CMAS-resistant material for TBCs, which shows a significantly enhanced CMAS resistance than the conventional 17 mol% YO_1.5-stabilized ZrO₂ (17YSZ). After exposure at 1300°C for 100 hours, the CMAS infiltration depth in ZYTO bulk is ~80 μm (for a 20 mg/cm² CMAS deposition), in contrast to ~700 μm in 17YSZ bulk (50 hours). Compositional and morphological analyses on the CMAS reaction zone reveal that the excellent CMAS resistance of ZYTO originates from the uniform corrosion through grain and grain boundary, along with densification of the reaction layer. The high CMAS infiltration rate of 17YSZ is attributed to the severe dissolution and infiltration through grain boundary. The reaction mechanisms of CMAS with ZYTO and 17YSZ bulks are discussed and a strategy of enhancing the CMAS resistance is proposed for ZrO₂-based TBC materials.     

Crystallization behavior of CMAS and NaVO3+CMAS mixture and its potential effect to thermal barrier coatings corrosion

Calcium-magnesium-alumina-silicate (CMAS) and molten salt corrosion pose great threats to thermal barrier coatings (TBCs), and recently, a coupling effect of CMAS and molten salt has been found to cause even severer corrosion to TBCs. In this study, the crystallization behavior of CMAS and CMAS+NaVO₃ is investigated for potentially clarifying their corrosion mechanisms to TBCs. Results indicated that at 1000 °C and 1100 °C, CMAS was crystallized to form CaMgSi₂O₆, while at 1200 °C, the crystallization products were CaMgSi₂O₆, CaSiO₃ and CaAl₂Si₂O₈. The introduction of NaVO₃ in CMAS reduced the crystallization ability, and as the NaVO₃ content increased, glass crystallization occurred at a lower temperature, with crystallization products mainly consisting of CaAl₂Si₂O₈ and CaMgSi₂O₆. At 1200 °C, CMAS+10 wt% NaVO₃ was in a molten state without any crystallization, which suggested that NaVO₃ addition in CMAS could reduce its melting point, indicating enhanced penetration ability in TBCs and thus increased corrosiveness.     

Failure mechanisms of calcium magnesium aluminum silicate affected thermal barrier coatings

Depth profiles of the phase composition of two examples of calcium magnesium aluminum silicate (CMAS) affected thermal barrier coatings (TBCs) from an aero gas turbine engine were obtained using a monochromatic and collimated beam of synchrotron radiation. One TBC was deposited by plasma spray and the other by electron beam physical vapor deposition. These examples were complemented with an X‐ray diffraction (XRD) study of mixtures of TBC zirconia powder and sand heated in a furnace. The XRD results were compared with electron backscatter images and energy dispersive spectroscopy studies of the cross sections and mixtures. It was found that when liquid, the CMAS enhances mass transport leading to the densification of the zirconia, which then leads to spalling because of the increased residual stresses generated on cooling. Even without spalling densification will reduce a TBC's ability to thermally insulate. The enhanced mass transport can also lead to destabilization of the zirconia if yttrium ions preferentially transfer to the liquid or greater stabilization if calcium or magnesium ions transfer from the liquid to the zirconia. Zircon also precipitates when the zirconium from the TBC reacts with the silicon in the liquid CMAS.     

Hot corrosion behavior of Y4Al2O9 ceramics for thermal barrier coatings exposed to calcium-magnesium-alumina-silicate at 1250 °C

The degradation of thermal barrier coatings (TBCs) by calcium-magnesium-alumina-silicate (CMAS) attack has become increasingly dramatic. Y₄Al₂O₉ ceramic, a new potential TBC candidate, has received an increasing attention. In this study, porous Y₄Al₂O₉ ceramic pellets, instead of actual TBCs, are used to investigate the CMAS corrosion resistance at 1250 °C. Results indicate that Y₄Al₂O₉ reacts with CMAS melt to form an impervious sealing layer mainly containing Ca-Y-Si apatite, which could mitigate CMAS further penetration. Once the sealing layer formed, further reaction would occur above the layer accompanying by the recession of sealing layer. This process is probably related to a solid state diffusion.     

The corrosion behaviors of thermal barrier material of M-YTaO4 attacked by CMAS at 1250 °C

The corrosion of YSZ TBCs attacked by calcium–magnesium–aluminosilicate (CMAS) is a serious problem. Yttrium tantalite (YTaO₄), a new kind of potential thermal barrier ceramic material, was expected to replace the YSZ to manufacture the TBCs because of its great thermophysical characteristics. In this study, porous YTaO₄ ceramic pellets, instead of actual TBCs, were used to investigate the CMAS corrosion resistance at 1250 °C. Results indicated that CMAS couldn't cover the whole surface of YTaO₄ pellets homogeneously because of low wettability between liquid CMAS and YTaO₄, in addition, there was almost no reaction layer after 4 h reaction. The XRD results showed that M-YTaO₄, M′-YTaO₄, Ca₂Ta₂O₇ and Y₂Si₂O₇ were the main four phases after reaction and there was no phase containing the elements of Mg and Al. Compared with YSZ TBCs, this new kind of potential thermal barrier ceramic material showed well resistance to CMAS corrosion.     

CMAS corrosion resistance,thermal shock resistance and numerical simulation of novel surface micromesh thermal barrier coatings

Thermal barrier coatings (TBCs) are widely used as insulating layers to protect the underlying metallic structure of gas turbine blades. However, the thermal cycling performance of TBCs is affected by their complex working environments, which may shorten their service life. Previous studies have shown that preparing a mesh structure in the bonding layer can relieve thermal stress and improve the bonding strength, thereby prolonging the service life of TBCs. In this paper, a micromesh structure was prepared on the surface of the bonding layer via wet etching. The microstructure and failure mechanism of the micromesh TBCs after CMAS (CaO-MgO-Al₂O₃-SiO₂) thermal erosion were investigated. Numerical simulation was combined with thermal shock experiments to study the stress distribution of the micromesh-structured TBCs. The results showed that the circular convex structure can effectively improve the CMAS corrosion resistance and thermal shock resistance of TBCs.     

Hot corrosion behavior of BaLa2Ti3O10 exposed to calcium-magnesium-alumina-silicate at elevated temperatures

Calcium-magnesium-alumina-silicate (CMAS) attack has been regarded as one of the significant failure mechanisms for thermal barrier coatings (TBCs). In this study, CMAS corrosion behavior of BaLa₂Ti₃O₁₀, a novel TBC material, is investigated at 1300?°C and 1350?°C for 0.5?h, 4?h, 12?h and 24?h. Results reveal that BaLa₂Ti₃O₁₀ has high resistance to molten CMAS infiltration, attributable to the formation of a dense reaction layer. X-ray diffraction, scanning electron microscope, energy dispersive spectroscope, transmission electron microscope confirm that the layer consists of apatite, celsian and perovskite phases. With increased corrosion duration, the layer retains good phase stability and the thickness increases. The formation of corrosion products and the reaction layer are discussed according to a dissolution-reprecipitation mechanism and the optical basicity theory.     

Lanthanum magnesium hexaluminate thermal barrier coatings with pre-implanted vertical microcracks: Thermal cycling lifetime and CMAS corrosion behaviour

Atmospheric plasma-sprayed (APS) coatings have a layered structure as well as lower strain tolerance and a shorter lifetime than EB-PVD coatings. In this study, TBCs composed of a LaMgAl₁₁O₁₉ (LMA) top coat and a NiCrAlY bond coat were prepared by APS coupled with dry-ice blasting to implant vertical microcracks in the top coat. The thermal cycling lifetime and CMAS corrosion behaviour of LMA-TBCs with pre-implanted vertical microcracks were investigated in detail. The results show that the LMA top coat possesses an improved proportion of vertical microcracks and that the corresponding TBC has an improved thermal cycling lifetime. The vertical microcracks in the top coats, which not only reduce the thermal stress but also improve the strain tolerance of TBCs, dramatically contribute to the improvement in the thermal cycling lifetime. Surprisingly, the CMAS corrosion resistance of LMA-type TBCs with implanted vertical microcracks is better than that of conventional TBCs with a typical layered structure.     

Synthesis and thermophysical properties of ATa2O6 (A = Co,Ni, Mg,Ca) tantalates with robust CMAS resistance

A new family of ceramic environmental/thermal barrier coating (E/TBC) materials, that is, ATa₂O₆ (A = Co, Ni, Mg, Ca), for high-temperature applications, are investigated and reported in this study. We focus on the synthesis and features of crystal structures, and on the mechanical and high-temperature properties. ATa₂O₆ oxides have an extraordinary phase stability (up to 1300°C), and their thermal expansion coefficients (6.2–7.3 × 10⁻⁶ K⁻¹) match those of SiC fiber-enhanced SiC ceramic matrix composites (3–7 × 10⁻⁶ K⁻¹). Their low thermal conductivities (min: 1.15 W·m⁻¹·K⁻¹) root in the slow phonon spreading speed and fierce phonon-phonon scattering process, and they will provide exceptional thermal insulation. Moreover, their hardness (5.6–8.8 GPa), toughness (1.4–1.9 MPa·m^1/2), and moduli (100–210 GPa) have good comparability with current E/TBCs. We propose the 33CaO-9MgO-13AlO_1.5-45SiO₂ (CMAS) corrosion mechanisms of ATa₂O₆ ceramics, and their robust CMAS resistance relies on the phase stability of CaTa₂O₆ oxides. The excellent high-temperature properties ensure that ATa₂O₆ can be used as E/TBCs to provide thermal insulation and CMAS corrosion protection.     

Calcium-magnesium-alumina-silicate (CMAS) resistant Ba2REAlO5 (RE = Yb,Er, Dy) ceramics for thermal barrier coatings

Calcium-magnesium-alumina-silicate (CMAS) attack has been a great challenge for the application of thermal barrier coatings (TBCs) in modern turbine engines. In this study, a series of prospective TBC candidate materials, Ba₂REAlO₅ (RE = Yb, Er, Dy), are found to have high resistance to CMAS attack. The rapid formation of a continuous crystalline layer on sample surface contributes to this desirable attribute. At 1250 °C, Ba₂REAlO₅ dissolve in the molten CMAS, accumulating Ba, RE and Al in the melt, which could trigger the crystallization of celsian, apatite and wollastonite crystals. Especially, the formation of the crystalline layer in the Ba₂DyAlO₅ sample is the fastest. This study also reveals that Ba is a useful element for altering CMAS composition to precipitate celsian. Thus, doping Ba²⁺ in yttria partially stabilized zirconia or other novel TBCs might be an attractive way of mitigating CMAS attack.     

CMAS (CaO–MgO–Al2O3–SiO2) resistance of Y2O3-stabilized ZrO2 thermal barrier coatings with Pt layers

Calcium–magnesium–alumina–silicate (CMAS) corrosion significantly affects the durability of thermal barrier coatings (TBCs). In this study, Y₂O₃ partially stabilized ZrO₂ (YSZ) TBCs are produced by electron beam-physical vapor deposition, followed by deposition of a Pt layer on the coating surfaces to improve the CMAS resistance. After exposure to 1250 °C for 2 h, the YSZ TBCs were severely attacked by molten CMAS, whereas the Pt-covered coatings exhibited improved CMAS resistance. However, the Pt layers seemed to be easily destroyed by the molten CMAS. With increased heat duration, the Pt layers became thinner. After CMAS attack at 1250 °C for 8 h, only a small amount of Pt remained on the coating surfaces, leading to accelerated degradation of the coatings. To fully exploit the protectiveness of the Pt layers against CMAS attack, it is necessary to improve the thermal compatibility between the Pt layers and molten CMAS.     

Enhanced calcium–magnesium–aluminosilicate (CMAS) resistance of GdAlO3 (GAP) for composite thermal barrier coatings

The impact of calcium–magnesium–alumino-silicate (CMAS) degradation is a critical factor for development of new thermal and environmental barrier coatings. Several methods of preventing damage have been explored in the literature, with formation of an infiltration inhibiting reaction layer generally given the most attention. Gd₂Zr₂O₇ (GZO) exemplifies this reaction with the rapid precipitation of apatite when in contact with CMAS. The present study compares the CMAS behavior of GZO to an alternative thermal barrier coating (TBC) material, GdAlO₃ (GAP), which possesses high temperature phase stability through its melting point as well as a significantly higher toughness compared with GZO. The UCSB laboratory CMAS (35CaO–10MgO–7Al₂O₃–48SiO₂) was utilized to explore equilibrium behavior with 50:50 mol% TBC:CMAS ratios at 1200, 1300, and 1400°C for various times. In addition, 8 and 35 mg/cm² CMAS surface exposures were performed at 1425°C on dense pellets of each material to evaluate the infiltration and reaction in a more dynamic test. In the equilibrium tests, it was found that GAP appears to dissolve slower than GZO while producing an equivalent or higher amount of pore blocking apatite. In addition, GAP induces the intrinsic crystallization of the CMAS into a gehlenite phase, due in part to the participation of the Al₂O₃ from GAP. In surface exposures, GAP experienced a substantially thinner reaction zone compared with GZO after 10 h (87 ± 10 vs. 138 ± 4 μm) and a lack of strong sensitivity to CMAS loading when tested at 35 mg/cm² after 10 h (85 ± 13 versus 246 ± 10 μm). The smaller reaction zone, loading agnostic behavior, and intrinsic crystallization of the glass suggest this material warrants further evaluation as a potential CMAS barrier and inclusion into composite TBCs.