Wear mechanisms of LCPC rock abrasivity test impellers of materials equivalent to TBM cutter head face tools

This study aims at performing the LCPC (Laboratoire Central des Ponts et Chaussees) rock abrasivity test to explore the wear characteristics of LCPC test impellers of different material hardness (i.e., 70-75 HRB; 46-48 HRC; 54-56 HRC; 60-61 HRC and 78-82 HRC). The LCPC tests were carried out on two hard and abrasive minerals quartz and garnet. In terms of weight loss, the test results showed an inverse relationship between the material hardness and corresponding ABR (g/t) values. Microscopic examination was conducted to study the wear mechanisms of selected impellers tested on both quartz and garnet samples. The micrographs of LCPC steel impellers showed furrow deformation accompanied by micro cutting and brittle fracture in the case of soft standard test impellers (70-75 HRB). When the material hardness of impellers was increased from (46-48 HRC) to (78-82 HRC) the wear mechanism began to show micro cutting and brittle fracture. For both minerals in general with increase in hardness of impellers there was a decrease in material deformation along with gradual increase in brittle fracture. In the case of the quartz mineral, higher amounts of weight loss of impeller materials and hence higher ABR (g/t) values were observed due to angular morphology of quartz compared to the rounded grains of garnet. When comparing ABR (g/t) of quartz against garnet, it was found to be increased by 48%, 57%, 59% and 147% when testing using impellers of 46-48 HRC, 54-56 HRC, 60-61 HRC and 78-82 HRC respectively.