The development of brazing technology for SiC/SiCf composites for the fusion reactor

applications

Collaboration: ENEA Frascati, Italy

Max Planck Institute of Microstructure Physics, Halle, Germany

Preparation of eutectic alloys:

The Si-Ti and Si-Cr eutectic alloys were prepared in an Ar plasma furnaceThe as obtained alloys were remelted several times in an high preasure e-beam

to obtained a fine eutectic microstructure

Microstructure of eutectic alloys

Light regions represent the Si2Ti intermetalic cmpound while the dark regions represent pure Si

SEM micrograph of the Si-Ti eutectic alloy

Manufacture of the SiC/SiCf junctions

The junctions were heated at a rate of 10 0C/min at 20 0C above the eutectictemperature, kept at this temperature for 5 min and than cooled down to room temperature at a rate of 20 0C/min

SEM cross section of the junction brazed with Si-Ti alloy

High magnification cross section

3 µmfibre

Si

Si2Ti

SiC matrix

SiC matrix

Si2TiSi

3 µm

SiC matrix

Si

5 nm

High resolution microscopy of the junction cross-sectionHigh resolution microscopy of the junction cross-section

• The interface between SiC-Si is atomically smooth• No amorphous layer was observed

Interface characterizationInterface characterization

Nanochemistry of the junctionsNanochemistry of the junctions

Si-L23 edge

C-K edge

Ti-L23 edge

50 nm

SiC

Si2Ti

SiC

Si2Ti

interface

SiC+Si2Ti

a)

c)

b)

103 eV 105 eV • No interdiffusion was observed

Mechanical testingMechanical testing

Behaviour at shearing test

• eutectic Si-16Ti and Si-18Cr alloys are suitable for joining SiC/SiCf composites

• the joints investigated did not show any defects in the brazing layer

• no interdiffusion or formation of additional phases was observed

• both Si-16Ti and Si-18Cr joints led to the conclusion that direct chemical bonds

• are responsible for the adhesion with the SiC/SiCf composites

• the shear tests of the joints of SiCf/SiC composites exhibit remarkable values

• of the bonding strength up to 140 MPa)

ConclusionsConclusions

B.Riccardi, C.A.Nannetti, J.Woltersdorf, E.Pippel, T.Petrisor, ”Joining of SiC based ceramics and composites with Si-16Ti and Si-18Cr eutectic alloys”. International Journal of Materials and Product Technology 20 (5-6): 440-451, 2004.

PublicationsPublications

B.Riccardi, C.A.Nannetti ,T.Petrisor, J.Woltersdorf, E.Pippel S.Libera L.Pilloni, “Issues of Low Activation Brazing of SiCf/SiC Composites by Using Alloys Without Free Silicon” Journal of Nuclear Materials, 329-33, 562-566 Part A AUG 1, 2004.

B.Riccardi, C.A.Nannetti, J.Woltersdorf, E.Pippel, T.Petrisor.”Brazing of SiC and SiCf/SiC composites performed with 84Si-16Ti eutectic alloy:microstructure and strength”. Journal of Material Science 37 (2002) 5029-5039.

B.Riccardi, C.A.Nannetti, J.Woltersdorf, E.Pippel, T.Petrisor. “High temperature brazing for SiC and SiCf/SiC Ceramic Matrix Composites”. Advanced SiC/SiC Ceramic Composites: development and Applications in Energy Systems, A.Kohyama, M.Singh, H-T.Lin and Y.Katoh eds, Ceramic Transactions Vol 144, The American Ceramic Society, Westerville (OH), 2002, pp 311-322.

B. Riccardi, C. A. Nanneti. T. Petrisor, M. Sacheti, A. Orsini, Italian Patent AN: RM2001A000101 (2001).