Reactive Fusion Welding for Ultra-High Temperature Ceramic Composite Joining

ABSTRACT: MO-SCI Corporation and Missouri University of Science and Technology have developed and evaluated fusion welding technology applicable to ultra-high temperature ceramic (UHTC) composite joining during a Phase I ceramic joining program. This Phase II program will improve arc and reactive plasma arc welding techniques and consumables to improve joint quality. Work in the Phase I resulted in demonstration of 44 mm- by 3 mm thick full penetration fusion welds in ZrB2-20 v/o SiC and ZrB2-SiC-B4C composites. Two preheat furnaces were constructed to eliminate thermal shock during welding. Several opportunities for fusion joint improvement were revealed by Phase I microstructure evaluation and mechanical behavior studies. This program will build on the joining successes in Phase I and commercialize ceramic welding technology. UHTC composite joining techniques, equipment, and welding consumables will be marketed to military and civilian partners following successful demonstration of the technology. Year 1 research efforts will develop high quality welded ceramic components for thermo-mechanical testing. Successful welds will be tested under simulated hypersonic flight conditions in a 30kW inductively coupled plasma torch at the University of Vermont (UVM). Proof of joint survivability under high thermal and mechanical loads will supplement the necessary marketing tools to commercialize ceramic fusion welding. BENEFIT: Results from this Phase II will be used to commercialize successful ceramic joining concepts that will decrease the maintenance cost of high wear and high temperature, ceramic based components. Commercial applications for the joining solutions outlined in this proposal include repair and remanufacture of large ceramic crucibles designed to contain molten metals and integration of ceramic wear components in large diesel engines. Weldability of HfB2-B4C composites may also enable certain fission reactor designs that require complex shaped neutron shielding. Fabrication of high burn-up fission reactor vessels from ceramics remains a significant hurdle. Ceramic welding can address the material fabrication hurdles that must be overcome to realize some high burn-up fission reactor designs. The proposed work in the Phase II program will not only develop ceramic welding expertise that is applicable to commercial applications, but it will generate a number of consumable welding products that will be commercialized for use with existing welding systems at ceramic fabrication shops. Military applications for UHTC fusion welding include repair, fabrication, and fixturing of combustor liners and nozzle divergent seals found on Air Force, Navy, Marine and Army turbine engines. Ceramic armor repair and integration of ceramic armor into military transport vehicles is another potential application for the ceramic welding identified in this work. Ceramic welding will enable armor designs that use ceramic armor tiles as load bearing structures rather than sacrificial or"parasitic"components. Weight reduction realized by increased use of lightweight ceramics as structural components will relate to large cost savings associated with reduced fuel consumption. Ceramic welding could increase the use of wear resistant metal diboride-carbide particulate composites in high wear applications by enabling adequate methods to affix ceramics to existing metal alloy designs. Low maintenance track wear components for the Bradley fighting vehicle or M1 Abrahams tank could benefit from wear resistant weldable ceramics.