In severe cases, metal peeling and large-area random scratches occur on the contact surface; In general, the mechanical damage of fag imported bearing refers to the appearance of groove marks at different levels on the alloy surface of bearing bush. Contact surface damage and ablation exist at the same time. The main reason for bearing mechanical damage is that it is difficult to form oil film on the surface of fag imported bearing or the oil film is seriously damaged.
Plastic deformation and cold work hardening occur on the outer surface layer, and the sliding fag inlet bearing is subjected to repeated action of cylinder pressure (impact load). The deformation capacity is lost locally, and the grain is gradually formed and continuously expanded. Then, with the falling off of wear debris, the loaded outer layer forms a hole. Generally, when the bearing bush is pitted, the pit first appears, and then the pit gradually expands and causes the cracking of the alloy layer interface. The crack extends along the parallel direction of the interface until it peels off. The main reason for the cavitation of sliding bearing is that the sudden change of the cross section of structural elements such as oil groove and oil hole causes strong disorder of oil flow, and bubbles are formed in the vacuum area of oil flow disorder, and then cavitation occurs due to the collapse of bubbles due to the increase of pressure. Cavitation usually occurs in the high load area of fag inlet bearing, such as the lower bearing bush of crankshaft main fag inlet bearing.
Fatigue pitting corrosion of fag imported bearing refers to fatigue pitting due to engine overload. The bearing is overheated and the bearing clearance at fag inlet is too large, resulting in fatigue damage, fatigue pitting corrosion or fatigue falling off in the middle of the bearing. This damage is mostly caused by overload, excessive clearance of F bearing, or unclean lubricating oil and foreign matters mixed in it. Therefore, attention should be paid to prevent the fag inlet bearing from overload and do not run at too low or too high speed; Adjust the engine to a stable state at idle speed; Ensure normal fag inlet bearing clearance to prevent engine speed from being too high or too low; Check and adjust the working condition of the cooling system to ensure that the working temperature of the engine is appropriate.
The chemical impurities (acid oxides, etc.) in the lubricating oil oxidize the bearing alloy to form acidic substances. The corrosion area of fag imported bearing alloy is generally impure lubricating oil. Cause the bearing alloy to fall off locally and form irregular small cracks or pits. The main reasons for the corrosion of fag imported bearing alloy are improper selection of lubricating oil, poor corrosion resistance of fag imported bearing data, or rough engine operation and high temperature.
Local high temperature is formed, and there is a small convex metal surface in direct contact between the journal and the friction pair of the bearing. In case of lack of lubrication and poor cooling, the fag imported bearing alloy is blackened or partially burned. This fault is often caused by too tight fit between journal and bearing; The lack of lubricating oil pressure is also easy to burn the fag inlet bearing.