Comparison of abrasion wear testing to an in-service feed hopper wear case

Feed hoppers are used to guide flowing ore in the mines. The flow of ore over the feed hopper plates creates a deep cavity at the point, where the ore dropped from the feeder hits the plates. The prevailing wear mechanism in the feed hopper plates is abrasion, which is known to cause marked economical losses in the mines, when worn out parts are replaced. Therefore, technologically optimal but also cost-effective selection of the materials used in the wear parts is of essential nature. Novel application oriented wear testing methods offer one solution for the challenges faced in the selection of materials for parts and components prone to severe abrasive wear.
Wear of the feed hopper side plates was tested in the laboratory set-up and compared to the in-service samples that had been used for 13 weeks in a chromite mine. The studied 500 HB and 600 HB quenched and tempered steel plates had a typical martensitic microstructure. The slurry-pot with a dry gravel bed (dry-pot) and the crushing pin-on-disc were selected as the wear test methods. Both of these abrasive test methods cause high-stress wear, crushing the rock and deforming the steel, but the contact conditions are different. In the dry-pot, the test samples rotate inside freely moving gravel bed, while in the crushing pin-on-disc, the cylindrical pin sample is pressed against the rotating disc covered with loose rock particles. Kuru granite and Kemi chromite ore were used as abrasives.
Although both selected test methods simulated the in-service conditions quite well, especially the abrasives used in the tests caused differences in the results. When the test abrasive was chromite, the wear rates were on a similar level with the in-service use. Moreover, when the wear rates of the two studied steels were compared with each other, in chromite tested samples the difference was closer to the in-service case. On the other hand, the chromite ore comminuted much faster than granite, and therefore the wear rates with chromite were lower compared to the tests conducted with granite. Furthermore, the granite abrasive showed also much bigger difference between the wear rates of the test steels (about 30%). Therefore, in general, granite is a favored option when comparing the overall high-stress abrasion properties of steels. However, in this particular case, chromite was a better choice for a test abrasive, because it simulated better the in-service environment.