Influence of Carbon on the Wear Resistance, Strength, and Hardness of Composites with a Fe−Cr–Mn–Mo–N–C Matrix

Abstract

Ingots of a composite with a Fe−Cr–Mn–Mo–N–C matrix and reinforcing particles in the form of MgO, Al₂O₃, and AlN conglomerates have been produced by aluminothermy, which is a version of self-propagating high-temperature synthesis (SHS). The ingots differed mainly in carbon content. It has been found that with an increase in carbon content in the composite from 0.01 to 0.50 wt %, its hardness rises from 238 to 271 HV and its wear resistance improves. The wear resistance has been estimated by abrasive testing under the conditions of dry friction between the sample and a fixed abrasive−electrocorundum Р400 grit (28–40 μm) and Р80 grit (200–250 μm) abrasive paper. As a measure of wear resistance, we chose a decrease in sample weight after tests. The pressure with which the test material acted on the abrasive was roughly equal to 0.25 N/mm², and the test time was 90 s. The loss in weight was been measured using VLR-200 balance. The hardness has been measured by Vickers hardness testing using an ITV-1-A hardness meter according to State Standard 2999-75 with a holding time of 10 s under a load of 30 kgf. It has been found that a rise in carbon content in the composite causes its embrittlement. It is noteworthy that in passing compressive strength tests samples with 0.01 and 0.16 wt % C remained intact, whereas those with 0.50 wt % C cracked. However, cracked samples continued deforming without complete breakdown up to a load that is maximum permissible for the test machine. The compressive strength has been estimated from the cracking load and has been found to be 3210 MPa. The ultimate compressive strength has been determined using an REM-100-A-2 multipurpose testing machine.