Deposition and characterization of Al–Si metallic TBC precursor on Mo–Si–B turbine materials

Jackson, J. E.; Olson, D. L.; Mishra, Brajendra; Lasseigne-Jackson, A.N.

doi:10.1016/j.ijhydene.2006.08.053

Cited by 11 publications

(2 citation statements)

References 7 publications

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“…A number of surface modifications have been used to improve the oxidation resistance of Mo‐Si‐B alloys. Deposition of Al‐Si metallic coatings has proved to be a feasible process 152. Pre‐oxidation at high temperatures is also effective at enhancing the oxidation resistance of Mo‐3.9Si‐1.5B 68.…”

Section: Oxidation Behaviormentioning

confidence: 99%

Mo‐Si‐B Alloys for Ultrahigh‐Temperature Structural Applications

Lemberg¹,

Ritchie²

2012

Advanced Materials

253

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A continuing quest in science is the development of materials capable of operating structurally at ever-increasing temperatures. Indeed, the development of gas-turbine engines for aircraft/aerospace, which has had a seminal impact on our ability to travel, has been controlled by the availability of materials capable of withstanding the higher-temperature hostile environments encountered in these engines. Nickel-base superalloys, particularly as single crystals, represent a crowning achievement here as they can operate in the combustors at ~1100 °C, with hot spots of ~1200 °C. As this represents ~90% of their melting temperature, if higher-temperature engines are ever to be a reality, alternative materials must be utilized. One such class of materials is Mo-Si-B alloys; they have higher density but could operate several hundred degrees hotter. Here we describe the processing and structure versus mechanical properties of Mo-Si-B alloys and further document ways to optimize their nano/microstructures to achieve an appropriate balance of properties to realistically compete with Ni-alloys for elevated-temperature structural applications.

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Section: Oxidation Behaviormentioning

confidence: 99%

Mo‐Si‐B Alloys for Ultrahigh‐Temperature Structural Applications

Lemberg¹,

Ritchie²

2012

Advanced Materials

253

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“…Lifetimes up to 1000 cycles (60/10 minutes at high/ambient temperatures) were obtained for these E/TBC systems from furnace cycling tests [31,32]. For Mo-Si-B alloys, only one study on thermal barrier coatings has been published in the literature [33,34]. In the latter work, a multi-layer architecture was proposed with mullite TBC and BSAS EBC on top.…”

Section: Introductionmentioning

confidence: 99%

PVD thermal barrier coating systems for Mo–Si–B alloys

Lange

Braun

Schulz

2017

Materials at High Temperatures

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Mo-Si-B alloys possessing melting points exceeding 2000°C are promising candidates for high temperature structural applications outperforming the service temperatures of the currently employed Ni-based superalloys. However, their oxidation behaviour is poor, in particular at temperatures below 1000°C, suffering from evaporation of MoO 3 . Application of protective coatings forming continuous silica/borosilicate scales is a viable approach to enhance the oxidation resistance. In the combustion environments of gas turbines, however, the oxide scales require environmental protection by ceramic topcoats which can moreover operate as thermal barrier coatings (TBCs). In the present feasibility study, Mo-9Si-8B (at.%) specimens were coated with different 5 -10 µm thick oxidation protective layers produced by magnetron sputtering. Their chemical compositions in at.% were Mo-70Al, Mo-46Si-24B, Mo-37Si-15B and Mo-47Si-24Al. On the pre-oxidised coated samples, ceramic topcoats of 7 wt.% yttria partially stabilized zirconia (YSZ) and gadolinium zirconate (GZO) were applied using electron-beam physical vapour deposition. The thickness of the TBCs was in the range between 145 and 160 µm. The specimens with the different TBC systems were exposed to air at 1000°C for periods between 20 and 100 h. Post-oxidation cross-sectional analyses were carried out to study microstructural characteristics of the coated specimens.Both as-deposited YSZ and GZO topcoats exhibited good adhesion to the pre-oxidised bond coats. After 20 h of exposure to air at 1000°C, the Mo-70Al bond coat was entirely degraded in the region near the suspension hole related to oxidation of uncoated substrate material. In contrast, the YSZ topcoat was tightly-adherent to the borosilicate scale grown on the Mo-46Si-24B bond coat. Similar results were obtained for GZO topcoats deposited on Mo-46Si-24B and Mo-37Si-15B bond coats. The TBC system consisting of GZO topcoat and Mo-47Si-24Al bond coat, which formed a mixed scale of silica and mullite-like oxides, survived 100 h at 1000°C. However, after this exposure time, the bond coats were approaching their lifetime due to the low layer thickness. Oxidation of the Mo-Si-B substrate occurring at unprotected areas around the suspension hole of the sample caused substantial degradation of the outer region of the GZO topcoat due to chemical reaction between MoO 3 and Gd 2 Zr 2 O 7 . This corrosion attack led to complete destruction of the TBC systems after 10 h of exposure at 1300°C.

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