Adhesion effect in dry rubbing metal-metal combinations

Rubbing metal - metal combinations

DETAIL

In dry rubbing metal - metal contacts adhesion occurs with accompanying high friction coefficients and wear rate. To illustrate the adhesion effect in dry rubbing metal-metal combinations some material pairs are tested in a Pin on Ring Tribometer. For all specimen illustrated in the picture above the same test conditions where chosen (F=100 N - 2 MPa, v=1 m/s, dry contact, test duration 30 min.).

Bearing steel (100Cr6) ring against specimens, from left to right:

combination µ [ - ] k [10^-15 m³/Nm]

100Cr6 -100Cr6 0.35 - 0.55 1.23

steel 600HV -100Cr6 0.40 - 0.55 1.23

bronze - 100Cr6 0.45 - 0.60 3.8

Teflon - 100Cr6 0.15 - 0.15 630

Brass - 100Cr6 0.15 - 0.25 800

Aluminum - 100Cr6 0.25 - 0.45 260

Conclusion
In all metal - metal combinations adhesion occurs. Typical adhesion effects are recognized by material transfer and an irregular groove pattern.
The coefficient of friction is maximal for materials with high shear strength! A friction load of half normal load may occur in dry rubbing metal - metal combinations.
For Teflon it is known that a low friction and a high wear rate can be expected. The wear rate of Aluminum or Brass or Teflon against steel is unacceptable large (class 6).
In the combination steel - steel or bronze - steel the wear rate is certainly not bad however, the coefficient of friction will be unacceptable.