A welding assembly for forming a weld along a welding interface of a work piece(s) using vibrations includes a welding tool and a thermal barrier. The thermal barrier is at least a chemical and/or mechanical insulating layer positioned adjacent to the welding tool, which minimizes the rate of dissipation of heat generated by the vibrations at or along the welding interface. The welding assembly may also include a wear-resistant layer adjacent to the thermal barrier, which protects the thermal barrier from damage or wear. The welding tool is a portion an anvil assembly and/or a sonotrode assembly. A method of insulating a welding tool includes applying or connecting a thermal barrier to a surface of the welding tool, and minimizing the rate of dissipation of heat generated by the vibrations at or along the welding interface using the thermal barrier, which includes an insulating layer.