Ali Legnos
Friction and Wear
HW 4
1.
At a low applied normal load, the wear rate is low and fine particles will erode off the surface.
There will be some oxidation. When the load increases and the wear rate increases, this indicates that
that particle size is increasing and the wear volume is increasing. The flash temperature is increasing,
but it is not high enough to fully oxidize the particles. When the load increases further, but the wear
rate decreases, this means that the flash temperature is high enough to fully oxidize the particles and a
tempered layer is created on the surface, increasing hardness and thus decreasing wear.
2.
The Wear Mechanism Map of steel is shown below
(http://www.ewp.rpi.edu/hartford/~ernesto/F2012/FWM/Pics/Wear/WearMechanismMap-Steel.png).
The chart shows what type of wear will result from a given sliding speed and applied pressure. Above
a given force, almost independent of sliding speed, seizure will occur, perhaps the result of high
temperatures that weld the two surfaces together. For low speeds and low force conditions, “ultra mild
wear” will result. At increased pressure and mid to low velocities, delamination wear occurs. As speed
increases, mild-oxidational wear occurs. Here, the flash temperature is not high enough to fully oxidize
the eroded particles, but the eroded volume will increase. As the velocity increases further, severeoxidational wear will occur. Here, near or full oxidization will occur, and wear rates may decrease due
to a layer of increased hardness formed on the surface due to high flash temperatures. At high
pressures of this velocity range, melt wear will occur. As pressure increases further, seizure will occur.