| abstract |
A pelletizing ring extrusion die (10, figure 2) comprises a die body having a plurality of holes 20, each hole 20 has a surface at least partially coated with a low-friction coating 40. The holes 20 include an inlet end opening 26 having a tapered portion 30 and a generally cylindrical passage way. The low-friction coating 40 may be any material that exhibits low friction while having sufficient wear, corrosion and erosion properties. The low-friction coating 40 may be at least 20 microns thick on the inner surface 36 of the holes 20 and may be comprised of a single layer or multiple layers where each layer may be one of a metal, ceramic or composite. The low-friction coating 40 may be applied to the inner surface 36 by metallurgically bonding the coating to a substrate. The pelletizing die may be made of stainless steel, carbon steel or superalloys. The low-friction coating 40 may include tungsten carbide materials, ultralow friction diamond-like carbon, molybdenum disulphide, Ti-Si-Cr-C-N based coatings, or WC/W based coatings. |