Abstract
Coal crusher is an important piece of equipment in the production of coal, but its abrasive wear remains a troublesome problem. A worn coal crusher damaged by abrasive wear is usually repaired by hardfacing weld deposit to prolong its lifespan. Currently, submerged arc welding with added metal powder is gaining interest as a hardfacing process. This study aimed to find alternative materials for hardfacing a coal crusher by submerged arc welding, possibly with powder added into the weld pool. Five samples were welded with a single hardfacing layer. Metal powders were added to some samples. The macroscopic structure and dilution of the deposited layer were examined using a stereo camera, across the cases. The chemical composition of the weld metal was investigated using an optical emission spectrometer. The worn surface layers, as well as the metallurgical structure of the hardfaced surfaces, were characterized optical microscopy, scanning electron microscopy, and energy dispersive X-ray diffraction. Mechanical properties were assessed from microhardness testing and abrasive wear testing. The results showed a variety of chemical compositions in the hardfaced deposit, depending on the type of wire used, the dilution of the weld metal, and the type of metal powder added. There are advantages and disadvantages to welding dilution of hardfaced metal, and the degree of dilution depends on the type of wire and added powder used. Carbon, chromium, manganese and nickel contents in the dilution layer and in the added powder with the welded metal lead to structures that are mixtures of martensite and austenite, and this combination greatly improves hardness and wear resistance. The addition of ferro-carbon-chromium produced intergranular carbides, which were a major cause of decreasing wear resistance of the martensite structure. The worn surfaces of hardfacing layer showed micro cutting, micro ploughing, and micro fracture.
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