Hardfaced wear resistant coatings for mining tools
Ahmed, Shahroz (2019)
Materiaalitekniikan DI-ohjelma - Degree Programme in Materials Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hardfacing is one of the methods to protect base material from severe wear and corrosion environment and provide life extension to the component. In this work, erosion resistance and impact resistance of four hardfacing alloys were tested in their as clad and post weld heat-treated conditions; two iron based alloys and two nickel based alloys were selected. The hardfacing was deposited by cold metal transfer (CMT) welding because the method provides the advantages of automated precise welding, low dilution, spatter free deposits and high degree of flexibility. Two cladding strategies were adopted while hardfacing; cladding on quench and tempered steel and cladding on soft annealed steel, which was later followed by heat treatment. The deposits were examined for their heat input, dilution, cooling time (T8/5) and deposition rate. The erosion resistance of the alloys was tested with pulse jet equipment and impact resistance was analysed with hammer mill test; both tests were conducted at Tampere University. After hardfacing, the samples were grinded and cut according to the dimensions that would fit in both test equipment. Before the test the samples were analysed for their microstructure, phase and hardness to differentiate the results of as clad and heat-treated conditions. After the erosion and impact tests, the wear depth of the samples was analysed with Alicona optical surface profilometer. It was revealed that post weld heat-treated samples are not suitable for high wear resistance and there are high chances that heat treatment produces crack in the heat affected zone. The results of the erosion tests and impact tests yielded that iron based alloys, in their as clad state, offer high wear and impact resistance as compare to the nickel based alloys.