Active Brazing of SiC-Base Ceramics to High-Temperature Alloys
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JMEPEG https://doi.org/10.1007/s11665-020-04934-3
Active Brazing of SiC-Base Ceramics to High-Temperature Alloys M. Singh, R. Asthana, and N. Sobczak (Submitted January 2, 2020; in revised form May 11, 2020) Active metal brazing of SiC-base ceramics and composites to Ti, Cu-clad-Mo, and nickel was carried out to screen promising commercial braze compositions with liquidus temperatures of 810-1040 °C. Microstructure, elemental composition, and microhardness were characterized using FESEM, EDS, and Knoop test in joints brazed using Ag-Cu-Ti alloys (Cusil-ABA and Ticusil) and a Ni-base alloy (MBF-20). Ti- and Si-rich interfacial layers developed in joints brazed using Ti-containing brazes, whereas Ni- and Sirich layers formed in joints brazed using Ni-base brazes. Monolithic SiC/Mo and SiC/Kovar joints with Cusil-ABA had sound interfaces and compressive shear strengths of 25-30 MPa. In the case of composites, surface preparation influenced bond quality: ground SiC-SiC samples led to sound joints and unground samples led to interfacial decohesion at low thermal strains whereas joints cracked regardless of the surface preparation at large thermal strains. Among SiC-SiC/metal joints, SiC-SiC/Cu-clad-Mo had the best microstructure and bond quality. Microstructures of joints made using MBF-20 mixed with low-expansion Si-X (X: Y, Ta, Hf, Ti, B) eutectic powders to control the thermal expansion are also presented. Keywords
brazing, ceramics matrix, composites, electron, joining, microscopy, optical metallography
1. Introduction A number of joining technologies and products based on them are commercially available for silicon carbide ceramics in niche applications that require hermeticity, elevated temperature strength, hardness, wear resistance, and durability. Over the years, interest has shifted toward SiC-base ceramic-matrix composites (CMCs) that contain a silicon carbide matrix reinforced with SiC fibers for use under harsh operating conditions. Since 2016, a SiC-SiC turbine shroud for a new aircraft engine, LEAP, has been used. A number of other SiCbase CMC components have been developed and evaluated for ramjet chamber for solid propulsion rockets, combustion chambers, and nozzles for liquid propellant rocket engines, stators, and disk blades in LOX/LH2 engines, thermal protection systems of space vehicles and other components and systems (Ref 1-3). The SiC-SiC composites are less prone to oxidative damage than CVI C/C composites, and compared to
This article is an invited submission to JMEP selected from presentations at the Symposium ‘‘Joining and Related Technologies,’’ belonging to the topic ‘‘Processing’’ at the European Congress and Exhibition on Advanced Materials and Processes (EUROMAT 2019), held September 1–5, 2019, in Stockholm, Sweden, and has been expanded from the original presentation. M. Singh, Ohio Aerospace Institute, 22800 Cedar Point Road, Cleveland, OH 44142; R. Asthana, Department of Engineering and Technology, University of Wisconsin-Stout, Menomonie, WI 54751; and N. Sobczak, Institute of Meta
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