Abstract: A method and related apparatuses are disclosed for coating an elongated filament, such as wire, wherein wire is coated with a heated coating material, such as polyetheretherketone (PEEK), and the coated wire is maintained at a temperature and for a period of time sufficient for a desired quantity and size of crystals to form in the coating material and to minimize internal residual stress. Thereafter, the coated wire is rapidly cooled to a temperature below its crystallization temperature, such as in a quenching bath. A crystalline PEEK coating results which has minimized internal residual stress, is less brittle, and has improved cracking, peeling and abrasion resistance over amorphous PEEK coating obtainable using prior methods.