Coatings tungsten carbide

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.)...

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. 

The MOCVD technique has also been used to deposit a number of refractory compounds for a wide range of applications. One of the advantages of this technique is the lower deposition temperature, which makes it very suitable for deposition on substrates, which are thermally sensitive, such as steels. Wear - resistant tungsten carbide coatings have been deposited on steel, using WF6 and suitable hydrocarbon gases at temperatures below 873 K.4,5... 

The heavy ion irradiation of the DLC films was performed2 using Uranium projectiles of 1 GeV with a dose of 1010 ions/cm2, i.e. 100 ions per pm2. The properties of these channels were studied by means of SFM using a conducting tip both diamond and tungsten carbide coated tips3 were used successfully. 

For better understanding of the CVD phase diagrams, examples based on single component system such as tungsten carbide coating and multi-component system such as mullite coating are discussed below for various process conditions. 

Ichijo S, Tamura K, Takano T, Nakao A, Hirahara T (1991) Properties and practical results of tungsten carbide coating produced by low temperature CVD process. J Phys IV2 C2-497-504... 

Tungsten carbide coats with a small proportion of tungsten carbide (up to max. 50%). 

Henke, H., Adam, D., Kohler, A., and Heimann, R.B. (2004) Development and testing of HVOF-sprayed tungsten carbide coatings applied to moulds for concrete roof tiles. Wear, 256, 81-87. 

Tungsten carbide coatings were also considered in addition to chromium oxide There is little to choose between tuem in respect of calculated flash temperatures. 

If a positive seal is required, both axial mechanical and radial mechanical seals are used. A radial seal, which uses two split, floating, carbon rings with a gas buffer riding on a tungsten carbide coated runner, is an example of an advanced design, permitting axial movement and both high- and low-temperature operation. 

Tungsten and carbon can form two carbides, namely WC and WjC. It is impossible to crystallize WC as a continuous deposit, because WC is formed at a certain excess of carbon, which is known to passivate the electrodeposition front [11, 12], Hence, the crystallization of tungsten carbide as a continuous deposit requires a finer control over the electrosynthesis process and should be carried out under conditions of W2C formation. Experiments at 1173 K showed that tungsten carbide coatings can be deposited from a melt containing 5 wt% Na2 WO4. When the Na2C03 content does not exceed 0.2 wt%, continuous deposits of W-W2C alloys (the composition of which also depends on the carbonate concenfiation) are deposited on the cathode. Continuous W2C deposits appear at a concentration of 0.2-0.5 wt%, continuous W2C-WC deposits appear at 0.5-1.0 wt% poorly adhered deposits of W2C-WC are formed at still higher concentrations. 

The resistance to wear and abrasion was tested on steel 45 samples with different coatings. The second body was made of quenched steel 45. The wear resistance of samples increased by a factor of 5-7 for molybdenum carbide coatings [5], 6-9 for tungsten carbide coatings, and 8-11 for zirconium diboride coatings. 

The abrasive resistance of steel 45 samples with tungsten carbide coatings increased by a factor of 4-6 [5]. For tungsten carbide and zirconium dicarbide coatings, the abrasive resistance increased by factors of 7-8 and 8-10, respectively (Figure 4.8.5). 

Table 19 Compares the abrasive wear resistance of tungsten carbide coatings applied by detonation gun, plasma, and high-velocity oxyfuel...

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