Influence of the DIN 3962 Quality Class on the Efficiency in Honed Powder Metal and Wrought Steel Gears

Figures & data

Figure 1. Schematic of the FZG back-to-back test rig: 1, test gearbox; 2, load coupling; 3, slave gearbox; 4, torque sensor; 5, motor. Source: The figure is created by Edwin86bergstedt and is not altered. The figure is licensed under the Creative Commons Attribution-Share Alike 4.0 International license, https://creativecommons.org/licenses/by-sa/4.0/deed.en

Table 1. Constants for A, B, and C in dip lubrication.

	61 Nm	94 Nm	183 Nm
A	2.19e-05	2.67e-05	2.78e-05
B	1.26e + 00	3.41e + 00	6.51e + 00
C	−5.80e-03	−1.00e-02	−5.40e-03

Table 2. Chemical composition of the wrought steel and powder metal materials.

	Chemical composition (wt%)
	Fe	Mn	Cr	Ni	C	S	P	Si
16MnCr5	96.95–98.78	1–1.3	1.1	—	0.14–0.19	≤0.035	≤0.025	0.4
Powder metal steel	98.8	0.5	—	0.5	0.2	—	—	—

Table 3. Number of gears tested and the quality class for the wrought steel and powder metal materials.

Index row
DIN 3962 quality class	6	7	8	≥9
16MnCr5	3	3	0	1
Powder metal steel	2	3	2	1

Figure 2. Overview of the in situ setup for measuring the gear flank.

Figure 3. Gear mesh efficiency for the wrought steel (W) and PM for all speeds at three tested torque levels (61, 94, and 183 Nm).

Figure 4. Gear mesh efficiency and reproducibility for wrought steel (W) and PM for all speeds at the highest torque tested (183 Nm).

Figure 5. Gear mesh efficiency values for each speed and quality class (QC) for the wrought steel (W) with an applied torque of 183 Nm. Each cell is colored according to the corresponding value, where higher efficiency values are depicted in lighter color.

Figure 6. Gear mesh efficiency values for each speed and quality class (QC) for the PM steel with an applied torque of 183 Nm. Each cell is colored according to the corresponding value, where higher efficiency values are depicted in lighter color.

Table 4. Average R_a and R_z surface roughness parameters with corresponding standard deviation and DIN 3962 quality class of the wrought (W) steel surface before and after efficiency testing.

	Surface roughness of the wrought steel gears
	Initial				After efficiency testing
Quality class	Ra	Ra SD	Rz	Rz SD	Ra	Ra SD	Rz	Rz SD
6	0.17	0.01	1.54	0.09	0.15	0.01	1.28	0.06
6	0.18	0.01	1.59	0.08	0.15	0.01	1.30	0.04
6	0.41	0.02	3.43	0.34	0.34	0.02	2.74	0.22
7	0.52	0.02	4.19	0.21	0.40	0.01	3.02	0.14
7	0.18	0.01	1.61	0.04	0.17	0.04	1.38	0.20
7	0.18	0.01	1.57	0.15	0.16	0.01	1.43	0.09
8	—	—	—	—	—	—	—	—
8	—	—	—	—	—	—	—	—
≥9	0.18	0.01	1.57	0.10	0.16	0.01	1.35	0.10

Table 5. Average R_a and R_z surface roughness parameters and corresponding standard deviation and DIN 3962 quality class of the PM steel surface before and after efficiency testing.

	Surface roughness of the powder metal steel gears
	Initial				After efficiency testing
Quality class	Ra	Ra SD	Rz	Rz SD	Ra	Ra SD	Rz	Rz SD
6	0.18	0.01	1.5	0.07	0.15	0.01	1.32	0.12
6	0.18	0.01	1.71	0.14	0.17	0.01	1.51	0.14
6	—	—	—	—	—	—	—	—
7	0.46	0.02	3.87	0.26	0.38	0.02	2.88	0.18
7	0.19	0.01	1.71	0.15	0.17	0.01	1.50	0.14
7	0.48	0.02	3.58	0.29	0.39	0.01	3.05	0.18
8	0.49	0.01	3.89	0.13	0.38	0.01	2.89	0.18
8	0.44	0.01	3.37	0.18	0.31	0.01	2.66	0.21
≥9	0.49	0.01	4.20	0.45	0.35	0.01	2.97	0.28

Figure 7. SEM images of representative surfaces after efficiency testing for the best and worst quality classes for both the PM and wrought steel material.

Figure 8. Abbott-Firestone bearing curves for PM with quality classes 6 and ≥9 measured after the efficiency test.

Figure 9. SEM image of PM with quality class 7; deformed asperities can be seen, as well as a region with closely packed dents forming a shallow pit.

Figure 10. Gear mesh efficiency and initial R_a surface roughness for wrought steel (W) and PM at the highest torque and speed tested (183 Nm and 20 m/s).