Apparatus and methods for thermally processing a workpiece include directing a plasma arc to the workpiece and using a dielectric shield or dielectric coating to protect a forward portion (e.g., a torch head) of a plasma arc torch. The dielectric shield or dielectric coating covers a nozzle disposed within the torch head and protects the nozzle from the effects of slag and double arcing. The shield also improves operator visibility due to the spatial relationship between the dielectric shield and the nozzle.