Cemented Carbide Industry Research Articles

When tungsten meets carbon

Tungsten carbide powder has proven to offer a key ingredient in cemented carbide manufacture. Its undisputable technological success is based on high purity in tungsten refining as well as robust and adaptable powder processing in mass production. Grain and particle size distribution and powder morphology can be varied to meet demand from alloy manufacture. In combination with third elements manifold sintered structures can be achieved. Circularity of tungsten carbide is mirrored by chemical and direct recycling methods including a variety of products. All these factors contribute to the potential to establish sustainable supply chains in the cemented carbide industry. This report combines a survey of today's industry standard and selected technological fields, which have been discovered during ten decades of powder development.

Sintering of High Mn Cemented Carbides in Mn-Rich Environment

The economic, environmental and healthcare aspects are pushing cemented carbide industry to reduce or even avoid the usage of conventional binder metals – nickel and cobalt. Commonly, austenitic Fe-Ni alloys have been preferred choice for substituting Co. Similar to Ni, manganese acts as austenite stabilizer and studies have shown that Fe-Mn alloys offer alternative binder metal to Co and Ni in cemented tungsten carbides. In addition, Fe-Mn as a binder potentially offers improved wear resistance due to the well-known wear properties of Fe-Mn-C steels. Addition of chromium to the binder composition increases corrosion performance of composite. Cemented carbides bonded with austenitic FeCrNi binder have demonstrated promising performance. In present work the possibility of achieving austenitic binder phase through substitution of nickel by manganese as an austenite stabilizer is investigated. Structure formation, phase composition and mechanical performance of WC-FeMn and WC-FeCrMn cemented carbides are discussed.

Micro-mechanical properties of new alternative binders for cemented carbides: CoCrFeNiWx high-entropy alloys

High-entropy alloys are a new type of materials with excellent properties that offer a great variety of possibilities due to the large degree of freedom in element composition. In particular, CoCrFeNiW alloys have recently attracted a lot of attention due to their potential use in solving the long-standing problem of substituting cobalt in the cemented carbide industry. The lack of experimental and theoretical studies on these multi-components alloys hinders their optimal development. In this work, we aim at filling in this gap by studying their mechanical properties employing first-principles alloy theory and experimental techniques. By using the calculated elastic parameters, we analyzed the mechanical stability, elastic anisotropy, Debye temperature, and derived polycrystalline moduli. Moreover, we fabricated CoCrFeNi and (CoCrFeNi)0.96W0.04 and analyzed them by means of X-ray diffraction and electron backscatter diffraction. The hardness and the Young’s modulus were measured. The Young’s moduli and the lattice parameters were compared to first principles calculations and good agreement was obtained. Hardness increases with the increment of W composition.

Cobalt oxide as a raw material for the production of WC-Co cemented carbides and its advantages for the pressing process

In general the cemented carbide industry uses cobalt as a raw material for the production of WC-Co cemented carbide. However the here presented publication shows that even if 100% of the cobalt of the cemented carbide is replaced with Co3O4 prior sintering, dense WC-Co cemented carbide can be achieved when the sintering program contains a hydrogen treatment. The point of the matter when using a cemented carbide powder which contains cobalt oxide (WC-Co3O4) are the huge differences in the compressibility compared to a conventional powder (WC-Co). Depending on the ratio of cobalt and cobalt oxide in the cemented carbide composition the compressibility of the powder/granule can be adjusted in a wide range. This opens up the possibility to produce different cemented carbide grades with an identical compressibility. As a consequence costs for additional pressing tools can be saved.

HISTORY OF DOMESTIC CEMENTED CARBIDES

Sintered cemented carbides are very important for modern engineering. It is difficult to point out an industry having no interest in cemented carbides. Their unique properties – hardness, strength, wear resistance, scale resistance, high temperature strength, corrosive resistance – make them suitable for different applications such as metal working, oil-well drilling, mining industry, chipless machining, arms industry, nuclear, space, vacuum and electric engineering, instrumentation, synthetic diamond fabrication process, etc. This paper provides an overview of domestic cemented carbide evolution and fabrication stages. The contribution of national researchers to the development of various cemented carbide grades and their fabrication progress is shown. The outstanding role of Professor G.A. Meerson in the cemented carbide industry development is mentioned. The paper cites the results of many Russian and CIS researchers from such leading institutes as the Russian National Cemented Carbide Research Institute (Moscow, Russia), Ukrainian Institute of Materials Science (Kiev, Ukraine), Institute for Superhard Materials (Kiev, Ukraine), Ural Branch of the Russian Academy of Science (Kirovograd, Russia), Ural Polytechnic Institute (Ekaterinburg, Russia), Tomsk Polytechnic Institute (Tomsk, Russia), Belarusian Institute of Powder Metallurgy (Minsk, Belarus), Institute of Metallurgy and Materials Science (Moscow, Russia), Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences (Chernogolovka, Russia).

Improvement of the compressibility of cobalt powders for the cemented carbide industry

The compressibility of cemented carbide granules is a very important factor to ensure reliability and repeatability of the pressing process. A main aim is to produce granules that can be pressed to compacts which exhibit a high density with a uniform distribution. This will result in less shrinkage and warpage during sintering. In the presented work it is shown that a correlation between the compressibility of the raw material powders (WC and Co) and the resulting cemented carbide granules exists. Furthermore cobalt powders with different characteristics were investigated in detail regarding the compressibility. The results show how the compressibility of cobalt powders can be improved by varying the particle distribution, the agglomeration and morphology. Subsequently also the resulting cemented carbide granules which include these Co powders showed a higher compressibility. On the other hand the oxygen absorption of the cobalt decreased the compressibility of the powder and the resulting cemented carbide granules.

History of cemented carbides in the Soviet Union

The history of the Soviet cemented carbide industry, which was presumably one of the biggest carbide industries worldwide in former times with 10 huge plants, the total annual production of over 7000 t of cemented carbides and nearly 25,000 employees, is almost unknown in the West. The first Soviet WC–10%Co carbide grade was developed and implemented by G.A. Meerson at the Moscow Electro-Plant in 1929 and had the brand name “POBEDIT”, the word originated from the Russian word POBEDA — victory. The brand name POBEDIT became a common noun soon, and even now many people use it to designate cemented carbide in Russia instead of the technically correct terms “hard alloy” or “hardmetal”. Nearly 16 t of POBEDIT were fabricated in 1931, which was more than the total estimated production of cemented carbides in the Western countries in the early 1930's. Later on, the carbide production was transferred to the Moscow Plant of Rare Chemical Elements and the full-scale production – from the fabrication of tungsten anhydride to sintered carbide articles – was started there in the beginning of the 1930's. In the late 30's the Plant was renamed as the Moscow Cemented Carbide Plant (MKTC) and is now part of Sandvik. The second Soviet carbide plant, Kirovgrad Hardmetal Plant (KZTS), was founded in the small town of Kirovgrad in the Ural region on the basis of equipment evacuated from Moscow in the beginning of the Second World War. The further growth of the cemented carbide industry in the Soviet Union and the foundation of a number of new carbide plants after the Second World War are described. The carbide research and development is also described with an emphasis on pioneering technologies and materials developed and implemented in the Soviet Union heralding those being presently state-of-the-art in the cemented carbide industry.

Wear applications offer further growth for PIM

PIM is having a significant impact on the production of wear resistant components from allowys, oxides, nitrides, and carbides. The good performance properties and availability of uniform feedstocks provide credibility to the technology. Potentially, the fabrication of wear materials by PIM will be one of the most profitable PM technologies. Unlike metallic systems (such as stainless steel), there is no raw material cost penalty associated with the hard materials, since they already start as powders. It is the shape complexity of new designs that is pushing traditional manufactures to examine injection moulding. If higher precision can be demonstrated, the conversion to PIM will proceed rapidly, since post-sintering finishing operations often constitute 40% of the manufacturing cost. Already the cemented carbide industry is acquainted with elements of debinding (dewaxing) and sintering, so they will succeed in directing new components to the process. This might be the next major growth wave for PIM following the spurt in stainless steels that started in the late 1980s.

Recovery of tantalum and niobium from solutions after crystallisation of ammonium paratungstate (APT) : T. Zhengji, (Cemented Carbide Industry Co., Zhuzhou, Hunan, China.) Int. J. Refractory Metals and Hard Materials, 10, No 3, 1991, 143–146

Recovery of tantalum and niobium from solutions after crystallisation of ammonium paratungstate (APT) : T. Zhengji, (Cemented Carbide Industry Co., Zhuzhou, Hunan, China.) Int. J. Refractory Metals and Hard Materials, 10, No 3, 1991, 143–146

Clinical findings among hard metal workers.

In 1940, the first report appeared describing a pulmonary disorder associated with occupational exposures in the cemented tungsten carbide industry. The disease, known as "hard metal disease," has subsequently been characterised in detail and comprises a wide range of clinical signs and symptoms. In this report, clinical findings in a group of 41 hard metal workers employed until recently are described. A high prevalence of respiratory symptoms was found. Thirteen workers (31%) had abnormal chest radiographs indicative of interstitial lung disease. Fifty per cent of these had been employed in hard metal manufacturing for less than 10 years. Abnormalities of pulmonary function were also frequent and included a restrictive pattern of impairment and decrease in diffusing capacity (27%). Associations were found between diffusing capacity, chest radiographic abnormalities and right ventricular ejection fraction at exercise indicating cardiopulmonary effects. The findings show the continuous need to control excessive occupational exposures to prevent hard metal disease, the history of which now enters its sixth decade.

Microstructure of WCTiCCo cemented carbides with rare earth (RE) additions: L Zhonglin, (Research Institute of Zhuzhou Cemented Carbide Industry Co, Hunan, China), Int J. Refractory Metals & Hard Materials, Vol 9, No 3, 1990, 128–131

Microstructure of WCTiCCo cemented carbides with rare earth (RE) additions: L Zhonglin, (Research Institute of Zhuzhou Cemented Carbide Industry Co, Hunan, China), Int J. Refractory Metals & Hard Materials, Vol 9, No 3, 1990, 128–131

Dust in the cemented carbide industry.

The paper reports on the air concentrations of cobalt at typical operations in the cemented carbide (hard metal) industry. Such samples were obtained in seven different plants.

Study on the Change of Grain Size of WC Powder during Ball Milling of Cemented Carbide

The mixing phenomena of WC and Co powders have not yet been made clear enough in spite of their importance in the Cemented Carbide industry. Therefore, in this paper the crushing of WC powders and the behaviour of their grain growth during sintering were examined using variousWC powders, i.e., coarse single crystal, coarse polycrystalline and medium single crystalline WC powders.The obtained results were as follows;(1) Coarse single crystal WC powders were crushed markedly by chipping in the early ball milling stage. There-after, average grain size of WC continued to decrease with the appearance of fine chipping powders. Therefore, the grain size distribution of the coarse single crystal WC powder grew wider with the increase of ball milling time.(2) Polycrystalline WC powders were crushed in the same way as the above mentioned (single crystal) in the early ball milling stage. However, the grain boundary destruction seemed to be caused after having been WC crushed into the definite size.(3) Single crystal WC powder of medium size were more difficult to be crushed with chipping than the coarse one.(4) The grain growth of coarse single crystal WC during sintering is more rapid than polycrystalline one because the size distribution of the former was wider than that of the latter. Moreover the average grain size of WC in alloys formed medium single crystal WC powders in coarser than that from coarse one, because the former was less crushed than the latter.(5) In sum, the crushbility of WC in ball milling and its grain growth in sintering did not only depend upon WC grain size, but also the manufacturing process.