U. Morkramer, M. Oechsle, Sulzer Metco WOKA GmbH, Barchfeld, Germany
Among the hardfacing processes Plasma Transferred Arc (PTA) welding is known for its excellent coating quality. Like Plasma Spraying the process uses powder shaped materials which enables highest flexibility in tailoring welding materials.
Components in the mining industry and oil and gas technology are often subjected to heavy abrasive wear which cannot be protected sufficiently with standard homogenous hard alloys. For these parts, mechanical blends of matrix materials and wear resistant carbides (mostly tungsten carbides) are widely used. To reduce machine downtimes it is mandatory to improve the tailoring of the coating materials to the specific wear regime. In addition, strong price increases in materials containing tungsten forces users and suppliers to look for suitable alternatives. Therefore new materials with other carbides such as chromium carbide need to be developed.
Based on a brief description of the materials mainly applied to date the influencing factors on the coating structure and wear properties are described. The investigations focus on Ni based alloys and tungsten carbide as reinforcing elements. New developments in tungsten carbide as well as materials containing chromium carbide are presented. Their wear behavior is characterized and discussed considering economical factors.
Summary: Different combinations of metal alloys and carbides were investigated regarding their wear resistance against sliding wear and erosion under different conditions to improve the lifetime of components in mining and oil and gas technology. The study focused on optimizing quantity, morphology, and grain size distribution of the carbides.
The results show that it is necessary to improve the tailoring of the coatings to the working conditions. Even slight minor changes to the wear regime can result in significantly higher wear losses.
