Grease Performance in Ball and Roller Bearings for All-Steel and Hybrid Bearings

Figures & data

Table 1. Material properties, steel versus bearing-grade silicon nitride (29).

Properties	Units	Bearing steel	Silicon nitride
Density	g/cm^3	7.8	3.22
Vickers hardness	GPa	7.8	12–15
Modulus of elasticity	GPa	206	310
Thermal expansion	10^--6/^°C	10.9	1.8
Maximum temperature	^°C	200	800
Poisson’s ratio	––	0.30	0.27–0.29

Fig. 1 Pressures and contact sizes of the DGBBs used here: (a), (c), (e) all-steel and (b), (d), (f) hybrid.

Fig. 2 Pressures and contact sizes of the cylindrical roller bearings used here: (a), (c), all-steel and (b), (d), hybrid.

Fig. 3. Grease life test result for DGBB using all-steel (blue) and hybrid bearings (red) with PU/E grease at nd_m=335,000 and 150°C.

Table 2. The grease types that used in this study for the DGBB tests.

Designation	Thickener type	Oil type	Viscosity (40^°C/100^°C)	VI	GPFs	GPFh	$GP{F}_h/GP{F}_s$
PU/E	Polyurea	Ester	70/9.4	112	2	15	8
Li/M/PAO	Lithium	Mineral/PAO	120/14	115	1.5	2.8	2
Li/M	Lithium	Mineral	41.2/7.5	151	1.3	3.2	3
LiC/M	Li-complex	Mineral	155/15.4	100	0.7	6.2	9
LiC/PAO/HV	Li-complex	PAO	220/26	150	0.6	1.1	2
LiC/M/HV	Li-complex	Mineral	220/19	97	0.5	2.3	5
LiC/PAO100	Li-complex	PAO	98/15.7	171	0.6	1.5	3
Li/M-S	Lithium	Mineral	100/10	74	0.6	––	––

VI = viscosity index; PAO = polyalphaolefin; HV = high viscosity.

Fig. 4. Grease life for DGBB using PU/E grease calculated back to 70°C.

Fig. 5. Grease life test result, calculated back to 70°C, for a CRB using all-steel (black) and hybrid bearings (red) with Li/M grease 100 and 120°C. b is the bearing factor used to multiply the speed factor nd_m.

Fig. 6. Grease life test result, calculated back to 70°C, using all-steel (black) and hybrid bearings (red) with LiC/M grease; tests executed at 120°C: (a) DGBB and (b) CRB.

Fig. 7. Grease life test result for a CRB, calculated back to 70°C, using all-steel (black) and hybrid bearings (red): (a) LiC/PAO/HV grease at 100 and 120 °C; (b) LiC/PAO grease at 120 °C; (c) Li/PAO grease at 120 °C; and (d) LiC/PAO100 grease at 120 °C.

Table 3. The grease types used in this study for the CRB tests with GPFs.

Designation	Thickener type	Oil type	Viscosity	$L_{50,\mathit{max}}$ steel (h)	$L_{50,\mathit{max}}$ hybrid (h)	GPFs	GPFh	Ratio
Li/M	Lithium	Mineral	41.2/7.5	27,800	39,920	0.6	2.8	2
LiC/M	Li-complex	Mineral	155/15.4	10,000	23,445	0.5	1.2	2
LiC/PAO/HV	Li-complex	PAO	220/26	27,800	39,920	0.15	0.5	3
LiC/M/HV	Li-complex	Mineral	220/19	10,000	23,445	0.25	1.3	5
Li/PAO	Lithium	PAO	100/14.5	27,800	39,920	0.25	0.6	2
LiC/PAO100	Li-complex	PAO	98/15.7	27,800	39,920	0.15	1.0	6

Fig. 8. Grease life test result, calculated back to 70°C, for a DGBB using all-steel bearings with Li/M-S grease at 110 120, and 130°C. The drawn line is calculated with Eq. [3] with GPF = 0.6. So the same performance as CRB with Li/M grease.

Fig. 9. Grease life for pure radial load. 6204-2Z bearing, calculated back to 70°C, with Li/M grease tested at 130°C. This result is used for comparing the DGBB tests, done at C/P = 65 and the CRB tests done at C/P = 32 (Eq. [8]).

ISO 26602. (2017), “Fine Ceramics (Advanced Ceramics, Advanced Technical Ceramics) Silicon Nitride Materials for Rolling Bearing Balls and Rollers.”

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