Coated tungsten carbide

In order to be able to state that a conductive probe works, it should be stable over at least several hours. This is principally a question of the wear resistance of the conductive coating and additionally of its ability to withstand high current densities or the resulting temperature. Within the production process one has to ensure that the very last nanometers of the tip are conductive [440]. Conductive diamond and other commercially available hard coatings (tungsten carbide, W2C, and titanium nitride, TiN), as well as some other metals evaporated in our in-house production, are used in our studies. 

When the performance and price of CVD tools compare favorably with those of PCD tools, CVD tools may displace PCD tools in some applications. Woodworking tools represent another major market segment for diamond coatings. Tungsten carbide blades already comprise a large part of the woodworking tool market. CVD-diamond-coated tools have yet to be used in woodworking and, thus, they offer an excellent business opportunity. 

Chaterjee, S. Edwards, A.G. Feigerle, C.S. Machining and morphological evaluation of diamond coated tungsten carbide drills. J. Mater. Sci. 2001, 35, 5707-5717. 

Similarly, various carbon-coated tungsten carbides were synthesized with HCP and K2WO4 as carbon and tungsten precursors, respectively (36). The gel intermediate was prepared with these two precursors and the heat treatment was carried out between 1123 and 1323 K under Ar flow. The phases obtained at 1123 K were WO3 -I- W metal that transformed to WC at 1273 K. A high specific surface area of 170 m /g at 1273 K was obtained due to the coated carbon structures. 

The main applications of coated tungsten carbide are tips and blanks, indexable inserts, milling tools, turning and boring tools, and circular saws. 

Murphy, C., Byrne, G. and Gilchrist, M.D. (2002) The performance of coated tungsten carbide drills when machining carbon fiber-reinforced epoxy composite materials, PI MECH ENG B-J ENG, 216 143-52. 

Hydrodynamic principles for gas bearings are similar to those involved with Hquid lubricants except that gas compressibility usually is a significant factor (8,69). With gas employed as a lubricant at high speeds, start—stop wear is minimized by selection of wear-resistant materials for the journal and bearing. This may involve hard coatings such as tungsten carbide or chromium oxide flame plate, or soHd lubricants, eg, PTFE and M0S2. 

Another important function of metallic coatings is to provide wear resistance. Hard chromium, electroless nickel, composites of nickel and diamond, or diffusion or vapor-phase deposits of sUicon carbide [409-21-2], SiC , SiC tungsten carbide [56780-56-4], WC and boron carbide [12069-32-8], B4C, are examples. Chemical resistance at high temperatures is provided by aUoys of aluminum and platinum [7440-06-4] or other precious metals (10—14). 

Thermal spray processes can be used to give coatings of chromium carbide or nickel chromium for erosion resistance, copper nickel indium for fretting resistance, tungsten carbide cobalt for wear and abrasion resistance, and even aluminum siHcon polyester mixtures for abradabiHty. 

Fig. 9. Representative micrographs of (a) single (TiC) and (b) double (TiN and TiC) coatings on cemented tungsten carbide (9).

Zinc, aluminum, nickel alloys, cobalt alloys and tungsten carbide are applied for sprayed coatings, which are slightly porous. Flame-sprayed zinc coatings are used for corrosion protection of steel and provide similar properties for galvanized coatings. 

Figure 12-7. Piston rods. Precision-manufactured rolled threads and induction hardening provide high fatigue strength and long life in heavy duty service. Standard rod material is AISI 4142 carbon steel other materials are available as required. Tungsten carbide coatings are also available for maximum surface hardness. Pistons are locked securely onto the rods. For higher pressure, smaller bore cylinders, the piston may be integral with the rod. (Used by permission Bui. 85084, 1992. Dresser-Rand Company.)...

Figure 12-8A. Piston rings. The piston rod is manufactured from heat-treated stainless steel and is coated with wear-resistant overlays, such as ceramic, chromium oxide, and tungsten carbide applied by plasma techniques. Piston rod cross-head attachment has mechanical preloading system for the threads. Rider rings and seal rings are manufactured from PTFE filled resins fillers are matched to the gas, piston speed, and liner specifications. Typical fillers are glass, carbon, coke, or ceramic. (Used by permission Bui. BCNA-3P100. Howden Process Compressors Incorporated. All rights reserved.)...

Roman, O. V., Kirilyuk, L., and Chernousova, S., Gas-Phase Precipitation of Tungsten Carbide Coatings,Metall, 6 53-56(1987)... 

Other potential applications are ceramic powders coated with their sintering aids, zirconia coated withyttria stabilizer, tungsten carbide coated with cobalt, or nickel, alumina abrasive powders coated with a relatively brittle second phase such as MgAl204 and plasma spray powders without the segregation of alloying elements. 

Thermal spray is a well-established, relatively low-cost, industrial processes which is used widely for the deposition of metals and compounds, including the refractory carbides and nitrides. Examples are coatings of tungsten carbide with a cobalt binder which are of major industrial importance. PI... 

Coates EO Jr, Watson JHL Diffuse interstitial lung disease in tungsten-carbide workers. Ann Intern Med 75(5) 709-716, 1971... 

Coates EO Jr et al Hypersensitivity bronchitis in tungsten-carbide workers. 64 390, 1973... 

The tungsten carbide has excellent wear characteristics and does not flake. Piston rods coated with tungsten carbide do not need recoating like chrome did except for external damage. The benefit to the user is longer operational life, thus, lengthening the period between overhauls. 

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