Lowest wear rate

At this point, experiments must be performed. Experimental results for the erosive wear of the selected candidate ceramic materials in coal slurries are presented in Table 8.4. Notice that the wear rate has a very rough inverse correlation with which is consistent with some of the descriptions of erosive wear from the previous section. Any of these ceramic materials is suitable for the piping and pump components based solely on wear rate, with the lowest wear rate for SiC being the most attractive. Formability and economic criteria can be applied to assist in the final material selection. 

Nonetheless, the wear-rate descriptions of Section 8.2.2 give ns at least a starting point in the material selection process. We once again see that ceramics and refractory metals will provide the best (lowest) wear rates. However, processability mnst be carefnlly evaluated for these materials, particnlarly for the refractory metals due to their high melting points. 

In summary, we can first say that there is no significant evidence that the low surface energy siloxane-modified epoxies reduce friction compared with the unmodified epoxy or the ATBN- and CTBN-modified epoxies. Based on the results of the steel ball-on-epoxy experiments, the most significant effect of the siloxane modifiers is the reduction of the elastic modulus associated with large closely spaced domains. The longer initiation times and lowest wear rates observed for the siloxane-modified epoxies were generally associated with a lower modulus. Epoxy modified with the CTBN of 18% AN content also showed lower wear rates with lower modulus but, in contrast with the siloxane-modified resins, had shorter initiation times with lower modulus. 

The experimental results suggest that, for these polylmides, the most flexible system had the lowest wear rate. Of the three polylmides tested, PIB should have the most flexible chain, as indicated by the glass transition temperature, because of the presence of the oxygen linking group. Chain rigidity is approximated... 

Conventionally, ultra-high molecular weight polyethylene is used for such applications with certain metallic alloys as counterparts. In comparison to this conventional polymer, PEEK and composites of PEEK with carbon fibers show the lowest wear rate on the counter metallic materials. 

Optimum PTFE loading of 15% in amorphous and elastomeric base resins and 20% for crystalline base resins provide the lowest wear rates. Higher PTFE loadings have minimal effects in terms of further reduction in wear rate, although the coefficient of friction will continue to decrease [56]. The effects of PTFE on the wear characteristics of various engineering resins are strongly dependent on the type of resin [57]. 

The highest wear rate is for liquid crystalline polymer and the lowest wear rate is for 30% glass fibre reinforced PA 4,6. 

Matrix/nano- particle Nanoparticle size Lowest wear rate achieved (lO mn /Nm) Optimum particle Reference content (vol.%)... 

Matrix polymer Nano-filler Surface treatment Lowest wear rate " (10 mm /Nm) Filler loading corresponding to the lowest wear rate Lowest frictional coefficient Filler loading corresponding to the lowest frictional coefficient Ref. 

With respect to the influence of filler content, it can be eoncluded that there is often an optimum filler loading corresponding to the lowest wear rate of the nanocomposites. Such a U-shaped dependence of wear rate on nano-filler concentration has been found in many reports, like the systematic investigations on PEEK composites filled with a series of inorganic nanoparticles. " " Nevertheless, the filler content dependence of frictional coefficient usually does not follow this rule. The frictional coefficient often decreases (or increases) slightly with increasing filler content and at times even varies irregularly with filler content. 

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