Friction silicon carbides

FIGURE 26.1 Experimental friction data (left) as function log speed at different temperatures and master curve (right) of an acrylate-butadiene rubber (ABR) gum compound on a clean dry silicon carbide 180 track surface referred to room temperature. (From Grosch, K.A., Sliding Friction and Abbrasion of Rubbers, PhD thesis. University of London, London, 1963.)... 

FIGURE 26.8 The friction master curves of the acrylate-hutadiene rubber (ABR) gum mbber on (a) dry glass, (b) dry clean silicon carbide 180, (c) dry silicon carbide dusted with MgO powder, (d) Alumina 180 wetted with distilled water, and (e) wetted with water +5% detergent. 

Silicon carbide is marketed as a surface enhancer (see Table 3.19). At levels of less than 10% it significantly improves the coefficient of friction and the wear resistance. 

Haishokuyaku (Gray Powder). A dark-gray, non-toxic exp cornpni No 1 Mixture con sisted of Amm Perchlorate 76.9, RDX 17.0, silicon carbide 1.3 paraffin 4.8% relative Power Brisance greater than for PA, but it is less sensitive to impact and friction. Used in Army Standard Demolition Blocks No 2 Mixture consisted of Amm Perchlorate 48, GuN (Guanidine Nitrate) 20, RDX 25 paraffin 5%. It was a commercial mining expl, and also used in Army Demolition Blocks (Rsf 1 p 28 R.ef 5, pp 365-66)... 

Abrasive modifiers are used in several types of friction materials. Very hard materials such as alumina, silicon carbide, and kyanite [1302-76-7] are used in fine particle sizes in organic, semimetallic, and cermet materials that are generally less than 74 im (200 mesh). Particle size is limited by the fact that large particles of such hard materials would groove cast-iron mating surfaces. Larger particle sizes are possible for harder mating surfaces in the special steel rotors used with sintered materials. 

Composite Plating. An electroless nickel matrix can be used to securely bond diamonds to cutting tools, and electroless nickel—diamond composites are also used (see Tool materials). The NYE-CARB process gives a silicon carbide—electroless nickel composite that has extremely high abrasion resistance (49). Electroless nickel—Teflon composites are being promoted as low friction materials. 

C. R. Blanchard and R. A. Page, Effect of Silicon Carbide Whisker and Titanium Carbide Particulate Additions on the Friction and Wear Behavior of Silicon Nitride, J. Am. Ceram. Soc., 73[11], 3442-3452 (1990). 

The silicon carbide-based ceramic layer is obtained by CVD activated by a microwave plasma (2.45 GHz) on the tantalum previously cleaned by an argon plasma (56 min, 133 Pa, 250 W) at a temperature identical to the deposition temperature (T = 570°C), lower than the substrate annealing temperature. After readjustment of the total pressure and microwave power by introduction of a precursor (TMS) in the argon flow, the SiC coating is produced under selected conditions (66 Pa, TMS/Ar = 0.2/5.5 l.h-, T = 570°C, 350 W) derived from a previous parametric study. Coatings obtained then presented low dry friction coefficients. The mechanical properties, which are essential in order to be able to appreciate the mechanical stability, were acquired by several methods ... 

H. Tomizawa and T.E. Fischer, Friction and wear of silicon nitride and silicon carbide in water Hydrodynamic lubrication of low-sliding speed obtained by tribochemical wear, ASLE Trans., 30, 41-46, 1986. 

Tomizawa et al. [217] performed pin-on-disk experiments on friction of SSiC against itself in water at room temperature. The authors found a friction coeflBcient of 0.26 and noted that wear of sintered silicon carbide occurs by a combination of tribochemical dissolution and the formation of pits by fracture of SiC grains. The amount of material removal varied from one SiC grain to the other, due to a strong dependence of tribochemical wear on crystallographic orientation of SiC grains. 

A A glass sphere is molded into an optical lens by pressing against an optically smooth silicon carbide surface under heat and pressure. In order to avoid surface irregularities and distortions due to friction between the two surfaces, a lubricant must be employed. Under the conditions of the process, what lubricating mechanism would you predict to be most effective What characteristics should the lubricant have Explain your conclusions. 

---