Research on Micro-Size Electrical Discharge Grinding Polycrystalline Cubic Boron Nitride Based on Single Pulse

Polycrystalline cubic boron nitride (PcBN) was a high temperature and high pressure composite material with high hardness. With its high wear resistance and good chemical stability, it conforms to the basic characteristics of modern advanced cutting technology of "high efficiency, high precision, high efficiency and green". Currently, it was widely used in the field of ferrous metal cutting tools. Electrical discharge grinding was one of the most effective methods for machining polycrystalline cubic boron nitride cutters. It was especially suitable for machining complex shapes and thin edge cutters. Single pulse electrical discharge grinding is the basis of continuous EDG machining and an effective method to study micro-scale electrical discharge grinding. In this study, the morphology of single pulse discharge corrosion pits and the relationship between discharge parameters and material removal rate, such as the deep-diameter ratio of the corrosion pits, the pulse width and the deep-diameter relationship of the corrosion pits, were studied with the polycrystalline cubic boron nitride composite sheet of 2 micron particle size as the test material and the independently developed single pulse discharge power supply as the device. The experimental results show that the radius and heat affected area of the discharge corrosion pit increase rapidly, then slowly, and finally gradually with the extension of pulse duration. The corrosion depth generally varies gently in the range of 0.2 ~ 0.5 micron, and the pulse duration has no obvious effect on the depth of the discharge corrosion pit. With the extension of pulse duration, the ratio of radius to depth of the corrosion pit changed in the range of 13 ~ 20, and the ratio basically declined.

The Geometric Surface Structure of EN X153CrMoV12 Tool Steel after Finish Turning Using PCBN Cutting Tools

The article presents the results of studying the effects of coated (TiN, TiAlN) and uncoated polycrystalline cubic boron nitride (PCBN) machining blades on the key geometric structure parameters of the surface of hardened and tempered EN X153CrMoV12 steel after finish turning. A comparative analysis of the use of coated and coated cutting tools in finish turning of hardened steels was made. Tool materials based on polycrystalline cubic boron nitride PCBN (High-CBN; Low-CBN) have been described and characterized. The advantages of using TiN and TiAlN-coated cutting tools compared to uncoated were demonstrated. The lowest influence of the feed on the values of all tested roughness parameters was noted for surfaces treated with TiN- and TiAlN-coated tools (both with 50 vol.% of CBN). For uncoated tools (60 vol.% of CBN) for feeds f = 0.2 and 0.3 mm/rev., the highest values of Ra and Rz roughness parameters were found. Moreover, the lack of protective coating contributed to the occurrence of intense adhesive wear on the flank surface, which was also in the range of the feed values f = 0.2 and 0.3 mm/rev. The analysis of material surface after treatment with the uncoated tools with the feed f = 0.2 mm/rev. showed the occurrence of the phenomenon of lateral material flow and numerous chip deflections.

Ultrasonic Deposition of Carbon Nanotubes on Polycrystalline Cubic Boron Nitride Composites

Polycrystalline cubic boron nitride (PcBN) are super-hard materials with high hardness and excellent abrasive resistance, widely used in cutting tools for precision machining of automotive and aerospace parts; however, their brittle properties make them prone to premature failure. Coatings are often applied to PcBN to extend their range of applicability and durability. Conventional coating methods are limited to the thickness range of a few hundred nanometres, poor adhesion to the substrate, and limited stability under ambient conditions. To further the properties of PcBN composites, in this paper, we explore the use of ultrasonic bonding to apply thick coatings (30–80 μm) on PcBN cutting tools. For the first time, a multi-walled carbon nanotube (MWCNT) powder is preplaced on a PcBN substrate to allow an unconventional coating technique to take place. The effects of ultrasonic bonding parameters on the change of mechanical properties of the coated tools are investigated through scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), micro-hardness analyses, and white light interferometry. The structure of the carbon nanotubes is investigated through transmission electron microscopy (pre coating) and cross-section of the bonded MWCNTs is studied via focused ion beam milling and SEM to evaluate the bonding between the multi-walled nanotubes. Optimum processing windows (i.e., bonding speed, energy, and pressure) are discovered for coating MWCNTs on PcBN. Focus ion beam milling analyses revealed a relationship between consolidation parameters and porosity of MW(pCNT) bonds. The proposed method paves the way for the novel design of functional coatings with attunable properties (i.e., thickness and hardness) and therefore improved productivity in the machining of aerospace and automotive parts.