The rolling bearing failure mode have surface touching fatigue, particle attrition, adhesion wear and corrosion wear, they always happened in bearing a work surface and surface layer, the quality of the surface of apparently bearing of the reliability and service life is the most important.
The rolling bearing work surface quality research include: surface morphology analysis; Surface materials and surface metamorphic layer analysis; Surface stress state analysis; Surface wear and corrosion state state analysis, and so on.
Due to cold, and heating conditions and lubrication medium factors, bearing working surface micro structure, physical, chemical, and mechanical properties of heart and often has the very big difference. Bearing surface microstructure and physical, chemical, and mechanical properties of the change in the surface layer called the surface badness layer. If the surface grinding badness layer is caused by the process is called grinding surface metamorphic layer. Rolling bearing surface metamorphic layer analysis is the work the surface quality of the main bearing analysis part, of course, is also bearing failure analysis is one of the important part.
According to the bearing surface work of grinding badness layer of formation mechanism, the influence of the main factors of grinding badness layer is grinding heat and grinding force.
1. Grinding heat
In grinding machining, grinding wheel and the contact area, and consume large amounts of can, have a lot of grinding heat, causing the grinding local instantaneous heat. Using the linear motion heat source heat transfer theory, calculation formula or application infrared method and thermocouple measurement method under the condition of the instantaneous temperature, can be found in 0.1 ~ 0.001 in the transient temperature ms grinding can be as high as 1000 ~ 1500 ℃. Such instantaneous heat, enough to make a work surface of certain depth surface layer produce high temperature oxidation, amorphous organization, high temperature tempering, secondary quenching, even burn cracking and so on many kinds of changes.
(1) surface oxidation layer
Under the action of instantaneous heat to the surface of steel and the oxygen in air role, rise into the very thin (20 ~ 30 nm) iron oxide thin layer. Note the oxidation layer thickness and surface grinding badness layer thickness test results is a total corresponding relationship. It shows that the oxidation layer thickness and grinding process directly related, is an important symbol of grinding quality.
(2) the amorphous organization layer
The instantaneous heat the grinding surface to melt condition, molten metal molecules flow and is uniformly apply to the work surface, and metal matrix at tremendous speed cooling, formed a very thin layer of the amorphous organization layer. It has high hardness and toughness, but it only about 10 nm, very easy in precision in grinding process has been removed.
(3) high temperature tempering layer
The instantaneous heat can make grinding surface certain depth (10 to 100 nm) in higher than to the heating temperature of heating the tempering. Do not meet austenitic transition temperature, as the heating temperature rise, the surface will produce step by step and heating temperature corresponding to the tempering or high temperature of tempering organization transformation, hardness is then drop. The higher the temperature of heat, hardness and more severe decline.
(4) second quenching layer
When the instantaneous heat the workpiece grinding surface layer heated to austenitic transition temperature (Ac1) above, the layer of austenite organization in subsequent cooling process, and to be hardened into martensite organization. Anyone with a second quenching burns workpiece, the second time under quenching layer must be very low hardness of high temperature tempering layer.
(5) grinding crack
Secondary quenching burns will make workpiece surface layer stress changes. Secondary quenching area in compression state, under which the high temperature back there is the biggest sand materials tensile stress, here is the most likely place of core crack. The most easy to crack the original along austenite grain boundaries spread. Serious burns will cause the whole grinding surface crack (a cracked) caused the crash.
2. Of the formation of the grinding force badness layer
In the grinding process, workpiece surface layer will be grinding wheel cutting force, compression force and friction role. Especially after both action, to make the work surface layer formation of plastic deformation, the direction of strong layer and processing hardening layer. These metamorphic layer will inevitably affect surface layer residual stress changes.
(1) cold plastic deformation layer
In the grinding process, and every moment grits is equivalent to an cutting edge. But in many cases, cutting edge horn before negative, grits in addition to cutting function besides, is to make the surface of workpiece under extrusion action (the plough role), make the surface layer of plastic deformation left obvious. The deformation of the deformation degree of as grinding wheel grinding blunt degree and grinding increases feed.
(2) thermoplastic deformation (or high temperature sex deformation) layer
In a work surface grinding heat of the formation of the transient temperature, make certain depth of workpiece surface layer elastic limit fell sharply, even to the extent of the elastic disappear. At this time in surface grinding force, especially compression force and friction force, under the action of the free extend caused by the limits of the metal matrix, the surface be compressed (more plough), in the surface layer caused the plastic deformation. High temperature plastic deformation in the grinding process under the condition of invariable, the surface with the increase of temperature increase.
(3) processing hardening layer
Sometimes use microhardness method and metallographic method can be found that, because of the machining deformation caused by increased surface hardness.
In addition to outside grinding, casting and heat treatment caused by heating the decarburization layer surface, after again if the machining process of is not completely place to remain in the surface will also cause surface softening metamorphism, facilitates the bearing early failure.




Other News:
The surface of the bearing surface layer and quality
The rolling bearing production characteristics
Bearing the rings round centerless grinding characteristics
Bearing the kinds of maintenance
Bearing collar is the characteristics of super let
Affect the failure reasons of bearing
Bearing collar super finishing process analysis
The ball of light steel ball process common defects