The frictional behavior of DLC films against bearing steel balls and Si3N4 balls in different humid air and vacuum environments

When conducting impact tests of protective glasses, nonunique cases of destruction of balls made of bearing steel ShKh15 were recorded. The causes of their destruction were determined. The state of the material was studied by fractographic and metallographic analysis, hardness and microhardness measurement. In the structure of the metal of all the balls, no critical defects were found such as flockens, shells and microcracks, but adverse factors were detected in the microstructure of the material, namely, the presence of fineneedle martensite with excessive carbides. It is established that the detected structural factors lead to liability to brittle fracture, an increase in the hardness of the material, a decrease in plasticity. To prevent brittle fracture of the balls and provide a reserve of plasticity of steel ShKh15 at high shock loads assessment calculations of ductility coefficient were made; and it was recommended to limit the maximum hardness of the material critical value HV=5.70 HPa (54 HRC), with the corresponding plasticity coefficient equal to 0.8.

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TiC/a-C Nanocomposite Coatings for Low Friction and Wear Resistance

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.3655 ◽

2005 ◽

Vol 475-479 ◽

pp. 3655-3660 ◽

Cited By ~ 4

Author(s):

Y.T. Pei ◽

Damiano Galvan ◽

Jeff T.M. de Hosson

Keyword(s):

Wear Resistance ◽

Friction And Wear ◽

Ambient Air ◽

Bearing Steel ◽

Nanocomposite Coatings ◽

Columnar Microstructure ◽

Low Friction ◽

Micro Cracks ◽

Steel Balls ◽

Wear Tests

TiC/a-C:H nanocomposite coatings have been deposited by magnetron sputtering and are composed of 2-5nm TiC nanocrystallites well separated by amorphous hydrocarbon (a-C:H) of about 2nm separation width. A transition from columnar to glassy microstructure has been observed with increasing substrate bias or carbon content. Micro-cracks induced by nanoindentation or wear tests readily propagate through the column boundaries whereas the coatings without a columnar microstructure show supertough behavior. The nanocomposite coatings exhibit hardness of 5~20 GPa, superior wear resistance and strong self-lubrication effects with a friction coefficient of 0.05 in air and 0.01 in nitrogen under dry sliding against uncoated bearing steel balls. Especially, the transitions from low to ultralow friction or the reverse are repeatedly switchable if the atmosphere is cycled between ambient air and nitrogen. The lowest wear rate is obtained at high humidity.

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Fatigue Life of High-Speed Ball Bearings With Silicon Nitride Balls

Journal of Lubrication Technology ◽

10.1115/1.3452596 ◽

1975 ◽

Vol 97 (3) ◽

pp. 350-355 ◽

Cited By ~ 21

Author(s):

R. J. Parker ◽

E. V. Zaretsky

Keyword(s):

Fatigue Life ◽

Silicon Nitride ◽

High Speed ◽

Bearing Steel ◽

Rolling Element Bearing ◽

Ball Bearings ◽

Rolling Element ◽

Low Mass ◽

Element Bearing ◽

Steel Balls

Hot-pressed silicon nitride was evaluated as a rolling-element bearing material. This material has a low specific gravity (41 percent that of bearing steel) and has a potential application as low mass balls for very high-speed ball bearings. The five-ball fatigue tester was used to test 12.7-mm- (0.500-in-) dia silicon nitride balls at maximum Hertz stresses ranging from 4.27 × 109 N/m2 (620,000 psi) to 6.21 × 109 N/m2 (900,000 psi) at a race temperature of 328K (130 deg F). The fatigue life of NC-132 hot-pressed silicon nitride was found to be equal to typical bearing steels and much greater than other ceramic or cermet materials at the same stress levels. A digital computer program was used to predict the fatigue life of 120-mm- bore angular-contact ball bearings containing either steel or silicon nitride balls. The analysis indicates that there is no improvement in the lives of bearings of the same geometry operating at DN values from 2 to 4 million where silicon nitride balls are used in place of steel balls.

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Bearing Vibration and Oil Film Thickness in Relation to Sphericity of Bearing Steel Balls

6th International Power Transmission and Gearing Conference: Advancing Power Transmission Into the 21st Century ◽

10.1115/detc1992-0078 ◽

1992 ◽

Author(s):

F. Itoigawa ◽

T. Nakamura ◽

K. Funabashi

Keyword(s):

Film Thickness ◽

Three Dimensional ◽

Large Error ◽

Bearing Steel ◽

Rotational Axis ◽

Ball Bearings ◽

Elliptical Cross ◽

Oil Film ◽

Bearing Vibration ◽

Steel Balls

Abstract The relationship between the bearing vibration and the sphericity of the steel balls used for ball bearings is experimentally investigated in consideration of the oil film in between the steel balls and raceways. The experiments are carried out on angular contact ball bearings (7208C and 7010C) under only thrust load. First, it is confirmed that the oil film thickness, which is measured on this bearing, virtually agrees with the value calculated by EHL theory. And even if there exists a considerably large error in the ball shape, it does not always necessarily rupture the oil film if it is sufficiently thick. Second, in a simple two-bearing-shaft system, the even-order undulation of form error of ball, especially, second-order undulation, can cause bearing vibration. Furthermore, when the ball has a three-dimensional shape like a rugby ball, with elliptical cross-sections, the ball determines its own rotational axis.

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