IPMD 14th Edition 2010-2011, 7 pages, 3712 words

Authors: Professor Janusz Konstanty, AGH University of Science & Technology, Faculty of Metals Engineering and Industrial Computer Science, Krakow, Poland.

Diamond tools made from a hot pressed or sintered mixture of diamond grit/metal powder held in a powder matrix are one of the fastest growing segments of the hard materials industry. Janusz Konstanty of the Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science & Technology, Krakow, Poland, looks at recent trends in materials, processes and applications for PM diamond tools.

Although the early use of diamond as an engraving tool goes back to 350 BC, the modern application of diamond tools is about 140 years old. In 1862 the Swiss engineer J.R. Leschot conceived the idea of making diamond drill bits which soon found practical application. The first diamond circular saw blades for cutting stone were developed by F. Fromholt in France in 1885. The early blades used carbonados set around their periphery and were utilised to cut limestone and marble. Progress in the tool production routes, by making good use of powder metallurgy (PM) techniques, resulted in developing diamond grit impregnated saw blades which were put into operation around 1940.

Subsequent developments in the tool manufacturing technology may chiefly be attributed to the invention of synthetic diamond. Natural diamond has been used for centuries and efforts to manufacture synthetic crystals also date back at least several hundred years. They had remained fruitless until 1953, when positive and reproducible results were obtained by a team of researchers at ASEA. In 1955, quite independently and entirely without knowledge of what ASEA had been doing, General Electric announced its capability to manufacture synthetic diamonds on an industrial scale and was first to apply for a patent.

Permanent progress in the diamond manufacturing technologies fostered the commercial importance of synthetic grits, which now accounts for over 95% of all industrial diamonds consumed. Over the past five decades, modern production techniques based on diamond tooling have been implemented into evolving areas of industrial activity, thus enabling jobs to be completed quicker, more accurately and at less cost. They revolutionised machinery and processing techniques in the stone and construction industries, road repair, petroleum exploration, production of various parts and components made of ceramics, cutting frozen foods, etc. The recent figures indicate that the demand for diamond abrasives reached an impressive volume of one billion carats in 2000, as compared with approximately 380 million carats in 1990 and 100 million carats in 1980. A broad classification of all diamond tools is given in Fig.1.

In the new millennium the market for diamond tools continues to grow rapidly. Nowadays the marked decline in the price of industrial diamond makes it a commoditised product capable of competing, in terms of its price/performance ratio, with conventional abrasives such as silicon carbide and aluminium oxide.......

Further sections of this article include:

• Tool composition 
• Fabrication process
  Matrix-diamond mix preparation Cold pressing
  Hot pressing
  Sintering
  De-burring
  Quality control
  Finishing operations
• Recent trends and developments
• Applications
  Sawing granite on multi-blade machines for production of tiles
  Contouring natural stone slab edges with profiled milling cutters
  Wire sawing of stone and concrete
• References

Figures and Tables:

Fig. 1 Classification of diamond tools

Fig. 2 The average quarterly Metal Bulletin free market price quotation for 99.8% cobalt cathodes

Fig. 3 Iron-base cobalt-free Cobalite CNF powder (left) and copper-base Next 200 powder (right)

Fig. 4 Natural (left) and synthetic diamond abrasives produced by using cobalt-base (centre) and nickel-base catalyst (right)

Fig. 5 Diamond abrasives coated with a single layer of titanium carbide (left) and an additional layer of nickel alloy (right)

Fig. 6 Diamond tool production process   

Fig. 7 Different types of diamond tool segments including: uniform (left), sandwich (centre) and combination of uniform and sandwich (right)

Fig. 8 Schematic representation of hot pressing

Fig. 9 Sintered beads and a wire saw used for sawing stone and concrete

Fig. 10 Selection of sintered diamond tool segments before attaching to blades and drill bits

Fig. 11 Zenesis segment with arrayed diamonds (Courtesy EHWA Diamond Ind. Co., Ltd., Korea)

Fig. 12 Different types of diamond impregnated tools (Courtesy EHWA Diamond Ind. Co., Ltd., Korea)

Fig. 13 Metal-bonded diamond tool used for fatigue proof pre-grinding of lead crystal glass (Courtesy Wendt GmbH, Germany)

Fig. 14 Scaletta system multi-blade saw cutting a granite block (Courtesy EHWA Diamond Ind. Co., Ltd., Korea)

Fig. 15 NC260 Contourbreton machine (Courtesy Breton S.p.A, Italy)

Fig. 16 Cutting a large block from the rock face (Courtesy EHWA Diamond Ind. Co., Ltd., Korea)

Fig. 17 Portable wire machine making a vertical cut in a concrete wall (Courtesy Hilti Corp, Liechtenstein)

Fig. 18 Multi-wire machines are increasingly used for sawing thick sedimentary and metamorphic stone slabs and as an alternative to the traditional steel shot gang saws used for granite block slabbing (Courtesy Co.fi.plast. Srl, Brasil)