The causes of serious wear of sprocket socket are as follows

(1) The higher the adhesive wear load is, the higher the surface temperature is, and the more serious the adhesive phenomenon is. For a certain hardness of metal materials, wear tests are carried out under different pressures, and the relationship between wear rate and pressure is obtained. When the pressure reaches more than 1 / 3 of the material hardness, serious wear will occur. According to the stress distribution diagram, the maximum stress contact point is the maximum pressure, which is 884.4 MPa. Because the quenching hardness of 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, and it is easy to form fatigue pitting on its friction surface. The index to judge the metal contact fatigue strength is the contact fatigue limit, which is the maximum stress without pitting under a certain number of stress cycles. The contact fatigue limit of 40Cr after surface quenching treatment σ 0h = hrc17 + 200 σ 0H=1016MPa。 According to the stress distribution diagram, the maximum stress of sprocket socket is 884.4 MPa. Its value is very close to the allowable contact fatigue limit of sprocket surface, and it is easy to cause pitting failure at the maximum stress. But because of the poor lubrication condition of chain wheel and chain, the pitting corrosion has not formed in time, which 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 sprocket.

 

(3) Abrasive wear

 

Because the chain is inevitably in contact with pulverized coal, a little pulverized coal is stuck on the chain, which is brought to the contact point of chain socket of sprocket. Pulverized coal contains a little hard sand, which will cause the material on the surface of sprocket to fall off during the friction process, which is abrasive wear. Abrasive wear is related to the hardness of friction material and abrasive. From the influence diagram of abrasive hardness on wear, it can be seen that when the hardness of abrasive is close to that of friction material, high-speed wear of friction material is caused, because coal powder is mixed with a little hard sand, which is also one of the main reasons to accelerate the wear of sprocket.