Laboratory support for production of nano-composites
Historically, CBN was designed to replace artificial diamond in processing of hard and superhard materials containing carbon, for example, chilled cast iron and hardened steels. With the improvement of properties of CBN composites, the tools based on them have been used for cutting of the manganese steel, carbon fiber composite, siliconized graphite, hard alloys.
There is a steady upward trend in the use of CBN on tool materials market. This can be explained by the increasing use of hard materials in the industry and the introduction of high-speed modes of metalworking.
Microbor began the serial production of CBN-based composite materials tools and started their supplies to Russian market in 2004. Next year the company entered the international market. In 2008 the brazed tools were launched that has greatly expanded the scope of products. An important innovation was the creation of composite materials using nanoparticles of CBN (NCBN), which is harder than a synthetic diamond.
The unique products of Microbor are highly demanded in the market, that attract investment from Rosnano corporation. As a result, about 960 million rubles were aimed at retrofit in 2010-2011, and on the territory of the National Research Centre Kurchatov Institute was created one of the world's most modern productions of CBN-based tools.
Currently, Microbor employs about 50 people. Major customers are mechanical engineering companies. Sales are conducted both directly and through a network of distributors.
The process and products
Microbor implements a full cycle of tool manufacturing, which includes the following steps:
•preparation of raw materials;
•mixing of the components;
•sintering of the composite;
•laser cutting of composites;
•brazing (of brazed blanks);
•grinding of the monolithic and brazed plates.
The composite materials developed by Microbor include CBN forming matrix and anoxic compounds mainly based on titanium, which form refractory binder. The grain size of the CBN, its content, and the properties of the binder significantly affect the composite properties.
Distinctive features of the composites from Microbor are high impact resistance and wear resistance, due to both the properties of the initial nano- and micro CBN and refractory ligament and optimally selected sintering parameters of materials. In addition, are retained high microhardness and thermal resistance inherent to normal CBN. This complex of features provide improved performance, surface quality and accuracy of machining of parts made of various materials including hard and abrasive, such as stellite and cast tungsten carbide.
The company manufactures tools for the entire range of operations from roughing to finish and superfinish machining. The main types of composites: MBR 6010M, MBR 7010M and MBR 7040M.
MBR 6010M has microhardness of 3400 kg/mm2 at a grain size of 3-5 microns and CBN content of 60 to 65%. Tools made of this impact-resistant composite optimally suited for high-speed rough turning and milling of solid materials mainly – steels.
MBR 7010M has a microhardness of 6500 kg/mm2 at a grain size of 0.3-0.8 microns and CBN content of 85 to 90%. Tools made of it are designed for rough and finish machining of cast irons, hardened steels and superhard materials, including tungsten- and cobalt- based alloys, as well as composite materials. Superhard cutting edge MBR7010M characterized by high resistance to wear and provides the highest quality of surface machining.
MBR 7040M has a microhardness of 4800 kg/mm2 at a grain size up to 1 micron. This cultivar with an average amount of CBN is intended for finish and superfinish machining.
The choice of the type of the composite is determined by the characteristics of the machined material and the cutting conditions. Microbor produces not only the tools of standard sizes, but also performs a special orders for non-standard products.
Microbor’s tools can be used with cooling or without it, which is especially important in the machining of thin-walled and precise parts. With the destruction of the instrument during operation the penetration of its particles into the body of the workpiece is impossible.
Laboratory: quality control and new developments
All batches of incoming raw materials are inspected to meet the specifications. Depending on the type of material, the following methods are used:
•X-ray phase analysis to evaluate the phase composition;
•static laser scattering to analyze the particle size distribution;
•determination of bulk density and moisture content;
•scanning electron microscopy;
•microanalysis to check for impurities;
X-ray phase analysis and scanning electron microscopy are carried out in the partner laboratories, for the other measurements Microbor has its own equipment.
In particular, for the analysis of particle size distribution the laser instrument Analysette 22 MicroTec Plus from Fritsch is used. Compact, versatile system is designed for measurement of particles in the range of 0.08-2000 microns. It is equipped with two modules for wet dispersion: the standard one – for measuring solids and suspensions, and the small capacity one – for control of small volumes in various liquids, including in organic solvents. This configuration enables to choose the optimum dispersion medium for the analysis of various powders. All measurements are performed by the techniques developed by Microbor.
Product quality is assessed on all major stages of the manufacturing process. The most important controlled parameters are microhardness and ceramic properties of the composite (average density and open porosity). For measuring of microhardness is used scanning nano-durometer NanoScan Compact, which is product of TISNCM Institute (Technological Institute for Superhard and Novel Carbon Materials) – Russian leader in analytical instrumentation for the research of physical and mechanical properties of materials. This device implements all the basic measurement modes, allowing both to get comprehensive information about the characteristics of the investigated surface topography and its mechanical properties. The most popular methods are dynamic contact scanning and instrumental indentation. Berkovich type diamond pyramid is used as the indenter. Hardness is measured in the range up to 80 GPa, modulus of elasticity – up to 1000 GPa. In Microbor the microhardness control is performed over the entire surface of the workpiece using the random scatter of the points of measurement, which allows to obtain reliable estimates of the average values of the elastic modulus and microhardness. Measurement procedures are largely automated. The control software allows you to configure any set of measurement procedures, and then given test sequence is performed without operator intervention. This feature is especially useful in a quality control of materials. The program performs batch processing of the experimental data and then outputting the results of measurements, including a wide range of statistical parameters.
Finished tools are tested for cutting properties with the subsequent control of the shape and size of wear.
"Production of superhard materials is a science-intensive technology, so we paid special attention to the selection of laboratory equipment, – says Anna Elfimova, manager of department of technology adoption. – The main criterion was the ratio of price and quality, and we can say that the choice was made successfully. The capabilities of the devices meet our objectives, they are easy-to-use and easy to maintain. The most high-tech – NanoScan Compact and Analysette 22 MicroTec plus – support remote diagnostics. Anyway, no serious problems with the reliability arose. We conduct calibration equipment annually, perform maintenance, if it is prescribed by the manufacturer, update the software. A significant advantage of NanoScan is the proximity and accessibility of its developers. This allows to get advice and even attract them to adapt the device for specific measurement procedures".
One of the major objectives of the company is to carry out R&D to improve the product. R&D are being conducted in two main directions:
•increase the wear resistance of tools by applying special coatings, composite materials components contents variation and improvement of the geometry of the cutting edge;
•reducing the cost of the composite.
Optimization of cutting processes on the customer's production site is a special area of operation, which successfully engaged Department of technology adoption.