Fusion welding of diboride-carbide ceramic composites

<p>"Plasma and pulsed plasma arc welding (PAW and PPAW) processes were used to fusion weld ZrB₂ containing 20 vol% ZrC. Varying welding parameters resulted in changes in weld pool shape and size, and the size of ZrB₂ grains within the fusion zone. For PAW processes that resulted in a keyhole fusion zone (full penetration), the arc to workpiece power transfer efficiency was estimated to be 2 grain lengths were observed to decrease between binary PAW FZs (~1 mm in length), and binary PPAW FZs (~0.8 mm in length), and an increasing aspect ratio for ZrB₂ grains in PPAW welds (up to 40:1) compared to PAW ZrB₂ grain aspect ratios (up to 25:1) revealed that growth of ZrB₂ was hindered in PPAW FZs. Grain growth was also observed to decrease with decreasing arc power. A high arc power resulted in high growth rates of ZrB₂ and a textured FZ, lower arc power FZs did not exhibit texture. A high current plasma arc (222 A) was used to increase the temperature of the weld pool, such that ZrB₂ growth would follow the arc thermal gradient. ZrB₂ growth occurred in the basal plane, giving grains a plate-like structure, where grain thickness increased by ledge growth. ZrB₂ grain sizes within the FZ were observed to affect the strength of weldments. PM flexure strengths were measured to be ~660 MPa and strengths were observed to drop to ~140 MPa for PAW weldments and ~170 MPa for PPAW weldments. Diffusion of C into the melt pool was observed to hinder ZrB₂ grain growth significantly (~150 µm maximum ZrB₂ grain size), and the average flexure strength of a ZrB₂-ZrC-C weldments was ~250 MPa."--Abstract, page iv.</p>

Name thesis:degree_name

Ph. D. in Ceramic Engineering

Grantor

Missouri University of Science and Technology

Year dc:date.available

2016

Author dc:creator

• King, Derek Scott

• Diboride
• Fusion welding
• Ultra high temperature ceramics
• Ceramic Materials

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/2387

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-3389