Interaction of Mn+1AXn phases with oxygen-poor, static and fast-flowing liquid lead-bismuth eutectic

Abstract

Select MAX phase-based ceramics were screened with respect to their potential susceptibility to environmentally-assisted degradation in an oxygen-poor liquid lead-bismuth eutectic (LBE) environment, both under static and fast-flowing exposure conditions. The majority of the MAX phases exposed to oxygen-poor ( 2.210-10 mass%) static liquid LBE for at least 1000 h at 500°C showed exceptional chemical compatibility with the heavy liquid metal, i.e., no evidence of LBE dissolution attack was observed, despite the absence of a continuous oxide scale on the surface of the exposed MAX phase ceramics. The local LBE interaction observed only with the Zr-rich MAX phases consisted in the partial substitution of Al by Pb/Bi in the MAX phase crystal structure and the in-situ formation of Pb/Bi-containing solid solutions. Moreover, the interaction of Zr-based MAX phases with static liquid LBE was accompanied by the dissolution of parasitic intermetallic phases, which facilitated the further LBE ingress into the ceramic bulk. The erosion resistance of select MAX phase ceramics was also assessed in oxygen-poor ( 510-9 mass%) fast-flowing (v ≈ 8 m/s) liquid LBE for 1000 h at 500°C. Despite the moderate LBE oxygen concentration, oxidation was the predominant corrosion mechanism, while no erosion damages were observed in the exposed MAX phase ceramics. The resistance of the MAX phase ceramics to both dissolution corrosion and erosion in contact with oxygen-poor Highlights  Exposing 11 MAX phases to oxygen-poor, static LBE showed little or no interaction.  The LBE/Zr2AlC interaction formed a new Zr2(Al,Pb,Bi)C MAX phase solid solution.  The LBE/(Zr,Ti)n+1AlCn interaction formed (Zr,Ti)n+1(Al,Pb,Bi)Cn solid solutions.  (Nb,Zr)4AlC3 showed the best erosion resistance in oxygen-poor, fast-flowing LBE.  MAX phases outperformed 316L stainless steels exposed to similar LBE conditions. Recently, Bentzel et al. studied the behaviour of several MAX phases in static liquid sodium, another Gen-IV coolant, up to 750°C for 168 h [21]. They reported that Ti3SiC2, Ti2AlC and Cr2AlC were stable, as well as their grain boundary phases. Ti3AlC2, however, showed signs of degradation along the grain boundaries and Al-depletion in the MAX phase grains [21].

Compatibility of Zr2AlC MAX phase-based ceramics with oxygen-poor, static liquid lead–bismuth eutectic

“…5b). It is believed that the ZrC grain clusters that happened to be present right under the sample surface acted as a protective layer against LBE ingress, as previously discussed [13]. The clear absence of such ZrC grain clusters in the LBE-affected region (cross-section y-y', Fig.…”

“…As the characterization of the LBE-affected Zr2AlC grains revealed the local formation of a new Zr2(Al,Bi,Pb)C MAX phase solution [13], it was decided to synthesize this new MAX phase solid solution by reactive hot pressing for detailed structural characterization. For this purpose, ZrH2 (grain size <6 μm, >99% purity, Chemetall, Germany), LBE (44.5 wt% Pb and 55.5 wt% Bi, MCP 124, 5N Plus Lübeck GmbH, Belgium), Al (<5 μm, >99% purity, AEE, USA), and C (<5 μm, >99% purity, Asbury Graphite Mills, USA) powders were mixed in Zr:Al:LBE:C  2:0.55:0.55:0.95.…”

“…Liquid metal corrosion mitigation strategies for Gen-IV LFRs typically aim at reactor operation within well-defined conditions of temperature, HLM oxygen concentration, CO, and component-specific lifetime [3] For particular applications, an alternative corrosion mitigation strategy consists in the development of new HLM-compatible materials, such as the MAX phase-based ceramics already tested in liquid Pb and LBE, showing promising first results [5,6]. The MAX phases are nanolaminated ternary carbides/nitrides with the Mn+1AXn general stoichiometry, where M is an early transition metal, A is an A-group element (typically groups [13][14][15] and X is C or N [7]. In general, the MAX phases are good thermal and electrical conductors, tolerant to mechanical damage, and machineable with conventional tools [7].…”

“…Earlier studies reported that the exposure of Ti3SiC2 and Ti2AlC MAX phase-based ceramics to oxygen-containing (CO  10 -6 -10 -8 mass%) liquid LBE and Pb formed m-thick TiO2 (rutile) and mixed TiO2/Al2O3 oxide scales or dissolved 'parasitic' phases, such as TiAl in oxygen-poor (CO < 10 -8 mass %) liquid LBE [5,6]. The reported test results have been summarized in a recent work by Lapauw et al [13]. In the same work, 11 different MAX phase ceramics were exposed to oxygen-poor (CO ≤ 2.2×10 -10 mass%), static LBE at 500°C for 1000 h. The tested MAX phases were the commercial grades Maxthal® 312 (nominally, Ti3SiC2) and Maxthal® 211 (nominally, Ti2AlC) alongside various lab grades (i.e., (Ti,Nb)2AlC, Ti3AlC2, Nb2AlC, (Zr,Ti)n+1AlCn, Ti2SnC, (Nb0.85,Zr0.15)4AlC3, Zr2AlC, and Zr3AlC2).…”

Cr2AlC MAX phase as bond coat for thermal barrier coatings: Processing, testing under thermal gradient loading, and future challenges

“…2 It is true that only few MAX phases might be interesting for bond coats, but other fields such as nuclear applications and solar energy can be also benefited from dense and pure coatings. [39][40][41] Increasing the number of potential application will attract experts and efforts to the field, which is essential to process dense and pure coatings. In addition, other structures such as MAB phases present a high potential for high temperature application and they have not been deposited so far.…”