Sample of grinding strengthening layer of spiral bevel gear steel

In order to observe the grinding strengthening layer of spiral bevel gear steel and the microstructure of the grinding surface, the surface part of the sample after grinding is cut into two halves by wire cutting, and half of them are tested by section microscopy. This method is relatively simple to prepare samples and has high detection reliability. The other half is cut out by wire cutting ϕ 2 mm * 4 mm metallographic samples are embedded to measure the microhardness of grinding surface under different grinding parameter combinations. The preparation process is shown in Figure 1.

After that, grind and polish the sample with metallographic sandpaper with abrasive particle sizes of 150 #, 200 #, 400 #, 600 #, 1000 #, 1500 #, 2000 #. When grinding with sandpaper with different particle sizes, the grinding direction shall be perpendicular to the grinding direction of the previous particle size to ensure that all the grinding marks generated in the grinding process of the previous particle size are covered. After the grinding of spiral bevel gear, apply W0 on the surface to be measured 5. Polish the surface of the sample with a polishing cloth on an automatic grinding and polishing machine. After polishing, put the spiral bevel gear into the ultrasonic cleaner and clean it with alcohol to remove the dirt on the surface.

After the spiral bevel gear is cleaned, use a dropper to drop 4% nitric acid alcohol solution on the detection surface. After corrosion for about 20s, clean it immediately with tap water. Put the corroded spiral bevel gear after cleaning and drying into the Kearns 3D laser confocal microscope, observe the microstructure of the detection surface, and obtain the microstructure change of the metamorphic layer and the microstructure of the grinding surface. At the same time, fm-300 microhardness tester is used to detect the microhardness gradient of the strengthening layer, and the hardness change trend diagram from the grinding surface to the center of the spiral bevel gear and the microhardness of the grinding surface of the spiral bevel gear are obtained.

The microhardness of grinding surface was measured by microhardness meter fm-300. It is calculated according to the size of the indentation of the diamond indenter with microhardness on the surface to be measured, as shown in Figure 2. Under the action of a certain load P, the diamond indenter is pressed into the surface of the tested sample. After completion, measure the average length d of the two diagonal lines of the pit, calculate the indentation area F through the diagonal length d, and then calculate the Vickers hardness value. The indentation area F and microhardness HV are calculated as follows:

Where, f is the indentation area, D is the diagonal length, P is the load, and HV is the microhardness.

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