Low-temperature aluminoborophosphate glass coatings on AlSi9Cu3: mechanistic correlations between composition, sintering behavior, and thermal barrier performance
Year: 2026
Type: article
Abstract: ABSTRACT The development of thermal barrier coatings (TBCs) for Al–Si–Cu alloys is limited by a fundamental thermomechanical conflict that combines the high coefficient of thermal expansion of the substrate with the narrow processing window imposed by the low melting point of aluminum. There is a lack of potentially lower-cost, low-temperature routes compatible with these alloys. In this exploratory study, aluminoborophosphate (ABP) glazes were formulated and applied to the AlSi 9 Cu 3 alloy as a potentially lower-cost and less processing-intensive alternative to conventional TBCs. Four formulations (FR02, FR03, FR04, FR06) were processed under identical conditions (475–525 °C/60 min) and analyzed systematically. Correlations were established between glass composition (P 2 O 5 /B 2 O 3 /Al 2 O 3 ratio, TiO 2 content, and alkali balance), rheological/electrokinetic behavior (viscosity and ζ), sintering temperature range (optical dilatometry), microstructure assessed by scanning electron microscopy (SEM) and quantitative fracture-surface image analysis, and effective thermal conductivity of the coated system determined by laser flash analysis (LFA, 19–300 °C). At 500 °C/60 min and 300 °C, the coatings reduced the effective thermal conductivity of the AlSi 9 Cu 3 + coating assembly by 93–96%, maintaining the hierarchy FR02 < FR04 < FR06 ≪ uncoated alloy. This reduction in effective thermal conductivity is primarily associated with the formation of a low-conductivity glass layer, while glass-network characteristics, residual pore morphology, internal interfaces, coating continuity, and the contribution of the metallic substrate also influence the effective thermal response. In addition, compositional adjustment of the aluminoborophosphate system enabled low-temperature vitrification (≤ 525 °C) and thermomechanical compatibility with the aluminum substrate. The results demonstrate that compositional control of rheology and densification enables successful low-temperature consolidation at 500 °C/60 min within the investigated 475–500 °C processing range and supports the development of low-temperature ABP glass coatings for moderate-temperature aluminum alloy applications.
Source: Ceramics International
Language: English
Subfield: Aerospace Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,830
Funders: Fundação de Amparo à Pesquisa do Estado de São Paulo, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Universidade Federal do Rio Grande do Sul, Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina, Agência Nacional do Petróleo, Gás Natural e Biocombustíveis
OpenAlex ID: W7202372356