(1) The greater the adhesive wear load, the higher the surface temperature, and the more serious the adhesive phenomenon. For metal materials with a certain hardness, the relationship curve between wear rate and pressure is obtained through wear tests at different pressures. When the pressure reaches more than 1/3 of the material hardness, severe wear will occur. According to the stress distribution diagram, the contact point of the maximum stress is the place with the maximum pressure, and its value is 884.4 MPa. As the quenching hardness at the chain socket is HRC48~52, the corresponding hardness value is 4800MPa. Therefore, the pressure is far less than 1/3 of the material hardness, so adhesive wear is not the main form of sprocket wear.
(2) Contact fatigue wear
The friction pair of chain wheel and chain is an alternating contact stress, which is easy to form fatigue pitting on its friction surface. The index to judge the metal contact fatigue strength is the contact fatigue limit, that is, the maximum stress without pitting under a certain number of stress cycles. Contact fatigue limit of 40Cr after surface quenching σ 0H=HRC17+200, calculated σ 0H=1016MPa。 According to the stress distribution diagram, the maximum stress value of the sprocket socket is 884.4 MPa. The value is very close to the allowable contact fatigue limit of the sprocket surface, and it is easy to cause pitting failure at the maximum stress. However, due to the poor lubrication conditions of the chain wheel and chain, the pitting corrosion has not formed in time and has caused wear. At this time, the main damage form is wear rather than pitting corrosion. Contact fatigue wear is the main form of sprocket wear, which basically determines the service life of the sprocket.
(3) Abrasive wear
Since the chain is inevitably in contact with the coal powder, a little coal powder is stuck on it and brought to the contact of the sprocket chain socket. The coal powder contains a little sharp sand, which will cause the material on the sprocket surface to fall off during the friction process, which is called abrasive wear. Abrasive wear is related to the hardness of friction materials and abrasives. It can be seen from the influence diagram of abrasive hardness on wear that when the abrasive hardness is close to the friction material hardness, the friction material will be worn at a high speed. Because the pulverized coal is mixed with a little hard sand, this is also one of the main reasons for accelerating the wear of the sprocket.
