Papers by Keyword: CBN Grain

Abstract: Continuous induction brazing with ultra-high frequency was proposed to braze the monocrystalline CBN grains using Ag-based filler alloy. The interfacial microstructure of the brazed specimen and the resultant morphology on the CBN surface was investigated and analogized by scanning electron microscopy (SEM) and energy diffraction X-ray (EDX). The experimental results showed that the bonding among CBN grains, filler alloy and steel matrix was achieved. The CBN grains were well wetted by the filler alloy and formed a massive support profile. Moreover, the active element Ti of the filler diffused markedly and gathered in the interfacial of matrix/filler and filler/grain respectively. Due to the short dwell time in brazing, the newly formed resultants grew in a short time. The resultants layer did not entirely covered the CBN grain, and discretely distributed on the surface of CBN grain. The size of the resultants was less than 200nm.

Abstract: Cubic boron nitride (CBN) abrasive grains with surface titanium-deposited film were heat-treated during 550-950°C for 60 min under high vacuum circumstance. Detailed interfacial compounds analysis by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion spectrometer (EDS), differential thermal analysis (DTA) indicates that the interfacial reactions are much dependent on the heating temperature to some extents, and the reaction products, TiN, TiB2 and TiB chiefly form the network structure. In particular, at 950°C the transition layers with excellent performance, CBN/TiB2/TiB/(TiB+TiN)/TiN/CBN, is realized.

Abstract: Alumina (Al2O3) bubble particles were added into the mixture of CBN abrasive grains, Cu-Sn-Ti alloy and graphite particles to prepare the composite blocks for porous CBN abrasive wheels. The specimens were sintered at the temperature of 920°C for the dwell time of 30 min. The bending strength of the composite blocks was measured by the three-point bending tests. The fracture surface of the blocks was characterized. The results show that, the content of alumina bubble particles does not take significant effect on the mechanical strength of the composite blocks. Even the lowest strength of the composite blocks, 98 MPa, is higher than that of the vitrified CBN abra-sive wheels. Cu-Sn-Ti alloy has bonded firmly alumina particles and CBN grains by means of the chemical reaction and corresponding products. Finally, the chip space was formed through the re-moval of the ceramic wall of the alumina bubble particles within the CBN abrasive wheel during dressing.

Abstract: Self-lubrication CBN abrasive composite blocks and corresponding grinding wheels were made through the sintering process of CBN grains, graphite particles and Cu-Sn-Ti alloy at 920° for 30 min. The mechanical strength of the composite blocks was measured by means of the three-point bending experiments. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) were employed to characterize the fracture morphology and the interfacial microstructure of the composite blocks. Dressing experiments were carried out and the graphite film on the CBN grain surface was observed. The results obtained show that the bending strength of the composite blocks with 5 wt.% graphite particles reached 116 MPa, which met the mechanical requirements of the working layer of the grinding wheels. Chemical joining has taken place at the interface of CBN/Cu-Sn-Ti and graphite/Cu-Sn-Ti during the sintering process. Graphite film has been formed and spread to the grain surface after dressing.

Abstract: Multilayer brazed CBN wheel segments based on graphite self-lubricating has been fabricated. The bending strength of wheel segments was measured and the fracture morphology of tested segments was detected. The results show that the bending strength of segments with CBN grains decrease to a small extent from 116MPa to 97MPa with the linear increase of graphite content from 5 wt.% to 15 wt.%. Due to the poor strength and certain stress concentration by the added graphite, the fracture interface transfers from the whole CBN grains to the bonding matrix with the increasing of the graphite. In addition, the pore sizes are decreased obviously.

Abstract: In order to dominate the wetting behavior of molten Ag-Cu-Ti alloy and control the brazing reaction at the joining interface, CBN abrasive grains were brazed using the composite filler of Ag-Cu-Ti alloy and 8 wt.% TiB2 particles. Ag-Cu-Ti alloy without reinforcing particles was also applied in the current investigation to compare with the composite filler. The characteristics of the joining interface and the reaction products were examined using optical microscope, scanning electron microscope, and X-ray diffraction instruments. Finally, the morphology of the CBN grains on the working surface of the brazed abrasive tools was observed. Results obtained show that the composite filler containing TiB2 particles distribute uniformly in the filler layer. Moreover, the interfacial chemical reaction of CBN grains and Ag-Cu-Ti alloy is restrained when TiB2 particles are added. The sharp edges of CBN grains are exposed fully due to the decreased wetting behavior of the composite filler.