The reasons for severe wear of the sprocket chain socket are as follows:
(1) The larger the adhesive wear load, the higher the surface temperature, and the more severe the adhesive phenomenon. For metal materials with a certain hardness, a wear rate pressure relationship curve was obtained by conducting wear tests at different pressures. When the pressure reaches more than one-third of the material's hardness, severe wear will occur. According to the stress distribution diagram, it can be seen that the maximum stress contact point is the point of maximum pressure, with a value of 884.4 MPa. Due to the quenching hardness of HRC48~52 at the chain socket, its corresponding hardness value is 4800MPa. Therefore, the pressure is far less than one-third of the material hardness, so adhesive wear is not the main form of sprocket wear.
(2) Contact fatigue wear
The friction pair between the sprocket and the chain is subjected to alternating contact stress, which can easily form fatigue pitting on its friction surface. The indicator for judging the fatigue strength of metal contact is the contact fatigue limit, which is the stress that does not cause pitting corrosion under a certain number of stress cycles. Contact fatigue limit of 40Cr after surface quenching treatment σ 0H=HRC17+200, calculated as σ 0H=1016MPa. According to the stress distribution diagram, the maximum stress value of the sprocket chain socket is 884.4 MPa. Its value is very close to the allowable contact fatigue limit on the surface of the sprocket, and it is relatively easy to cause pitting failure at the maximum stress. However, due to poor lubrication conditions between the sprocket and chain, pitting corrosion did not form in time and has already caused wear. The main form of damage at this time 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
Due to the inevitable contact between the chain and coal powder, a small amount of coal powder adheres to it and is carried to the contact point of the sprocket chain socket. The coal powder contains a small amount of sharp and hard sand, which can cause the material on the surface of the sprocket to fall off during friction, which is abrasive wear. Abrasive wear is related to the hardness of friction materials and abrasives. From the influence diagram of abrasive hardness on wear, it can be seen that when the hardness of abrasive is close to the hardness of friction material, it causes high-speed wear of friction material. This is also one of the main reasons for accelerating sprocket wear due to the mixing of coal powder with a small amount of sharp and hard sand.