Improvement in Abrasive Wear Resistance of Metal Matrix Composites Used for Diamond-Impregnated Tools by Heat Treatment

This work presents the possibilities of producing a substitute for a commercial matrix material for sintered metal-diamond tools which is characterized by increased tribological properties required in machining natural stones and concrete. In this study, the improvement in wear behavior of sintered pre-alloyed matrix caused by a thermal treatment was investigated. Several mixtures made of commercially available powders were homogenized by ball milling and consolidated at 900 °C using the spark plasma sintering (SPS) method. During cooling down, the specimens were subjected to isothermal holding at 350 or 250 °C for 1 h. After consolidation, all specimens were tested for density and hardness, whereas selected specimens were characterized by scanning electron microscopy (SEM) and flexural strength tests. The specimens made of BDCM50 powder (a mixture of the base and pre-alloyed powders in 50:50 proportion) shows excellent properties including σ0.2 = 1045 MPa in the three-point bending test and HV10 ≈ 380. Resistance to abrasive wear evaluated in both three-body and two-body conditions in the MWT abrasion test was estimated at Ai3=18.1±3.9 μm/20 m and Ai2=95.9±11.8 μm/20 m, respectively. A series of diamond-impregnated specimens (segments) was also produced and tested for wear rate on abrasive concrete. The potential graphitization of the diamond grits was investigated using Raman spectroscopy and X-ray diffraction. As a reference, both the base Fe-Mn-Cu-Sn-C and commercially available Co+20%WC alloy were used to compare selected properties of the investigated materials. It has been proved that heat-treated specimens made of the base mixture modified with pre-alloyed powders are characterized by increased hardness and resistance to abrasive wear. The BDCM50 matrix has a negligible effect on diamond graphitization and shows excellent field performance, which makes it a good potential substitute for replacing Co+20%WC in sintered diamond-impregnated tools.

Strengthening Mechanisms and Retention Properties of Sintered Iron-Based Matrix Material for Metallic-Diamond Tools

This work presents the analysis of mechanisms controlling the deformation strengthening of the surface during abrasion and their impact on structural changes and mechanical properties of Fe-Mn-Cu-Sn-C matrix material, which was prepared by means of powder metallurgy (PM). The powder mixture was ball-milled for 8 h and densified to <1% porosity using hot pressing at 900 °C and 35 MPa. Phases and structural transformations taking place in austenite during plastic deformation were identified. The participation, distribution, and morphology of the phases, as well as the physicomechanical properties of the matrix material, were tested. It has been shown that during grinding, deformation twins are generated in areas where an austenitic microstructure is present. To test the ability of the matrix to keep diamond crystals firmly cylindrical (Ø11.3 mm× 5 mm), diamond-impregnated specimens containing diamond grits of 30/40 mesh in size and at a concentration of 20 (5% vol.) were prepared. It was finally determined by the diamond-retention index, which is the number of retained diamond particles compared to the total number of diamond particles and the pullouts on the working surface of the segment. This research shows that materials containing Ti- and Si-coated diamond particles, deposited by the CVD method, have the highest abrasion resistance and, therefore, have the best retention properties. In order to determine the bonding mechanism at the matrix-diamond interface, specimens were also analyzed by SEM and TEM.

Improvement in Hardness and Wear Behaviour of Iron-Based Mn-Cu-Sn Matrix for Sintered Diamond Tools by Dispersion Strengthening

The work presents the possibility of fabricating materials for use as a matrix in sintered metallic-diamond tools with increased mechanical properties and abrasion wear resistance. In this study, the effect of micro-sized SiC, Al₂O₃, and ZrO₂ additives on the wear behaviour of dispersion-strengthened metal-matrix composites was investigated. The development of metal-matrix composites (based on Fe-Mn-Cu-Sn-C) reinforced with micro-sized particles is a new approach to the substitution of critical raw materials commonly used for the matrix in sintered diamond-impregnated tools used for the machining of abrasive stone and concrete. The composites were prepared using spark plasma sintering (SPS). Apparent density, microstructural features, phase composition, Young's modulus, hardness, and abrasion wear resistance were determined. An increase in the hardness and wear resistance of the dispersion-strengthened composites as compared to the base material (Fe-Mn-Cu-Sn-C) and the commercial alloy Co-20% WC provides metallic-diamond tools with high-performance properties.