Steel, frictional coefficient composites

Table II presents the specific wear rates (in mm /Nm, volume loss per unit load per unit sliding distance) and average kinetic friction coefficients of the composites sliding versus steel and silicon nitride, upon initial and continued sliding. Plots of friction coefficient versus sliding duration in kilocycles (1 kc = 107 m) are shown in Figures 2-5, for all experiments. All composites formed transfer films upon sliding against both steel and silicon nitride. The films were similar in appearance under optical microscopy, and covered approximately 30% of the contact region.

Steel Counterface. Wear and friction against steel, for all composites except LlWl, indicate excellent lubrication. Friction coefficients are near the minimum, and wear rates near the maximum, of the "low friction, low wear" regime delineated for a wide variety of polyimides by Fusaro (y. 

Figure 2. Friction coefficient as a function of sliding duration for LI composites sliding against steel.

The wear properties of PEEK-based composites filled with 5% nanometer or micron AI2O3 against the medium carbon steel are improved by the addition of AI2O3. In contrast, the friction properties are not improved. However, the filling of 10% poly(tetrafluoroethylene) (PTFE) into pure PEEK results in a simultaneous decrease of the friction coefficient and the wear coefficient of the filled composite. ... 

Figure 5.1 Relationship between the friction coefficient and load of 20% glass fibre reinforced PEI and 20% glass fibre reinforced PSU fibre composites against AISI 4140 steel, at different sliding speeds. Reproduced with permission from Z. Demir, Journal of Polymer Engineering, 2009,29, 8-9, 549. 2009, De Gruyter...

Answer by author The friction coefficient of solid PTFE bodies on stainless steel surfaces in liquid nitrogen is essentially unaffected by the filler. Friction coefficient is normally 0.08. Wear of the unfilled PTFE is 3 to 10 times that of the material considered in this report. A more complete answer can be found by referring to the paper "Wear and Friction of Filled Polytetrafluorethylene Compositions in Liquid Nitrogen" by D. W. Wisander, C. E. Maley and R. L. Johnson, ASLE Transactions, Vol. 2, No. 1, pp. 58-66, April, 1959. 

The friction coefficient is a mechanical parameter, which depends on the surface material composition and the nature of the surface itself. Fig. 4 presents the relative friction coefficient for the samples treated at different gas composition. It relates the friction coefficient of the treated sample to the value of the untreated stainless steel (0.78). The measurement of the friction coefficient has been done for different number of tracks. For pure nitriding, after the first 2000 tracks, at which the wear depth is lower than 0.6 pm, in all examined treated samples, the friction coefficient is reduced to 59 %. While the C2H2/N2 gas ratio increases, the values of the friction coefficient decrease significantly and reaching approximately 14 % for pure carburizing. As a function of gas composition, the friction... 

The friction coefficient and the specific wear rate of the nanocomposites were determined by sliding wear tests on a block-on-ring apparatus against a 100 Cr 6 (German standard) steel ring as the counterpart. A pressure of 1 MPa and a velocity of 1 m/s were used over a duration of 20 h for each sample. Additional wear tests of the composite systems were carried out under fretting test conditions against a ceramic ball as the counterpart. 

Variation of friction coefficient against steel with sliding speed for a range of vinyl ester and epoxy matrix composites tested at 1 MPa contact pressure in dry sliding. 

Suzuki et al ° made hot-pressed composites of molybdenum disulphide 80%, molybdenum dioxide 10% and niobium 10%. They were pressed at 25 MPa and 1500°C in carbon dies, and the flexural strength was 59 - 63 MPa and the elastic modulus 27.9 MPa. To improve the strength they added 5% of 304 stainless steel, and this gave a flexural strength of 69 - 80 MPa and elastic modulus 43.8 MPa. The coefficient of friction of the latter compact was 0.07 to 0.18 and the specific wear rate 2.2 x 10" mm Nm at 450°C in vacuum. 

F. 3 Speed dependence of coefficient of friction (p) ftom mini-traction-machine measmements for different compositions of HEPES-glycerol mixtures with ( ) and without ( ) polymer. A rotating steel ball is brought into contact with a rotating glass disk under an applied load of 10 N and with a track radius of 20.7 mm. The mean speed of the ball and disk varied from 0 to 2500 mm/s with a SRR of 10%... 

Fig.l7 shows that the surface of the composite is smooth and a small amount of defect area can also be observed. The smooth surface is mainly because of the friction between the ceramic material and the steel ring. The friction chip has high surface activity and easy adheres to the material surface, forming the continual surface layer on the surface with the increase of wear time. The smooth and continue surface layer can effectively reduce the coefficient and slow the wear. With the temperature of friction area increase, wear increase because of the plastic deformation and material transfer take place, form the adhesive wear. 

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