Cast Iron Counterface Research Articles

Tribological performance of bronze-filled PTFE facings for machine tool slideways

The friction and wear behaviour of bronze-filled PTFE facings against cast iron has been investigated under dry conditions in the laboratory. The work shows that the surface of the PTFE composite becomes enriched with bronze particles during sliding, owing to the preferential wear of the PTFE matrix. This contributes to the improved wear resistance of the composite, since the particles block the slip of the PTFE lamellae. The results also indicate that the onset of equilibrium wear after running-in is due to the development of a continuous PTFE transfer film on the cast iron counterface which shields the cast iron from further chemical adhesion and presents a much less aggressive surface to the PTFE counterface. A load-dependent transition from mild to severe wear was found at 54 N and occurred whether the PTFE was used as the flat plate or the pin. Failure of the PTFE facing occurred catastrophically owing to fracture in the adhesive with the failure thickness and time both decreasing with increasing load.

Effect of fabric geometry on friction and wear of glass-fibre-reinforced composites

Glass-fibre-reinforced poly(vinyl)-butyral-modified phenolic composites with reinforcements of woven roving, plain weave and satin weave glass fabrics were made. The friction and wear characteristics of the composites were studied on a pin-on-disc apparatus against a cast iron counterface under dry-sliding conditions. Experiments show that the geometry of the reinforcing fabric has a significant influence on the friction and wear behaviour of the composites. The wear rate of the plain weave glass fabric composite is lower than that of the woven roving and satin weave composites, while the woven roving composite exhibits greater tensile, flexural, impact and interlaminar shear strengths. The results are discussed on the basis of existing wear models of the composites.

Friction and wear of a glass woven roving/modified phenolic composite

The friction and wear behaviour of a glass woven roving/poly(vinyl) butyral modified phenolic composite, sliding under dry conditions against a cast iron counterface, has been investigated. Friction and wear of the composite show a marked dependence both on sliding velocity and normal pressure. Microscopic observations of the worn surface indicate that the higher wear loss and low friction coefficient for the composites at higher sliding velocities as well as at higher normal loads is probably due to fracture of weft fibres of the glass woven roving fabric reinforcement. The results are discussed on the basis of existing wear models of composite materials.

Wear behavior of graphite-fiber-reinforced glass

Composites of borosilicate glass reinforced with high strength, high modulus and ultrahigh modulus (UHM) graphite fibers were tested for wear against a cast iron counterface in a pin-on-disk configuration at sliding velocities of 0.24, 0.60 and 0.96 m s −1 under a load of 5 MPa. Discontinuous fiber-reinforced composites generally exhibited higher wear rates and friction coefficients than the continuous fiber-reinforced systems. Continuous UHM fiber-reinforced pins exhibited the lowest wear rate. It is shown that the wear rate depends on the strength and dimensions of the graphite filaments. Two types of wear, mild and severe, were observed at low and high sliding velocities. Mild wear is characterized by a smooth thin stable film on both the pin and the counterface with minimal pitting and plastic deformation of the cast iron. Severe wear is characterized by rough pitted surfaces on the pin and the counterface accompanied by a thick film on the counterface. A proposed mechanism of wear of unidirectional graphite-fiber-reinforced composites which incorporates the transition between mild and severe wear can explain the phenomenological observations.