Due to the limitation of the benchtop microhardness tester size, the surface hardness test of large nitrided parts is mostly carried out using a portable Leeb hardness tester, but the test results of the Leeb hardness tester often have a large test result with the micro hardness tester. The difference. In this paper, the hardness of the samples, workpieces and workpiece dissection samples were measured by using the Leeb hardness tester and microhardness tester. The causes of the difference in hardness test were analyzed, and the recommendations for the surface hardness test of nitrided parts were proposed. 1. Test methods and results As shown in Fig. 1, it is mainly taken as the tooth sample A, the flange portion sample B, and the furnace nitride sample C, the material 42CrMo. Among them, the weight of the ring gear is 20kg, and the size of the sample is φ30mm×φ 5mm×5mm. After the workpiece is nitrided, the tooth surface and the flange surface cut by the illustrated sample are sanded by hand to a good finish. The hardness is detected by a Leeb hardness tester, and then the teeth and flange parts are separately cut. For example, 2N and 10N forces were applied to the benchtop microhardness tester along with the furnace sample to test the surface hardness. The test results are shown in the attached table. Since the nitriding sample C is small in the furnace and does not meet the testing conditions of the Leeb hardness tester, the Leeb hardness test is not performed; for each sample, the 2N force is used in the benchtop microhardness tester, and the nitride layer is examined by the hardness gradient method. The sampling depth of the nitrided parts is measured every 0.05 mm from the surface, and the hardness and distance from the surface are shown in Fig. 2. Surface hardness test result 2. Analysis It can be seen from the schedule data and the hardness gradient that the hardness of the nitriding hardness measured by the benchtop microhardness tester is higher than that of the Leeb hardness tester, whether it is 2N or 10N. The difference between the 2N force hardness values ​​is large, and the 10N force hardness difference is slightly smaller. As a result of the hardness gradient method, the depth of the nitride layer was about 0.35 mm. The microhardness method is a method of pressing the hardness value of the test material. Its physical meaning characterizes the plastic deformation ability of the material surface against the diamond quadrangular pyramid pressing. According to the principle and method of Vickers hardness test, Vickers The hardness can reflect the soft and hard features of the surface of the metal material, and the loading load is small, so that the hardness of the surface of the nitrided layer can be accurately measured. The test principle of portable Leeb hardness is a dynamic load test method. From the material mechanics, it is known that the hardness value is related to the elastic modulus of the material and the absorption energy of the material. It can be seen that the accurate hardness value of the nitriding hardened layer can not be measured by using the Leeb hardness tester. Only the qualitative comparison test of the surface hardness of the same material and process nitriding parts can be used. The hardness tested can only be used as a reference and cannot be judged. Whether the nitriding hardness is acceptable. 3. Suggestions (1) Each furnace shall be provided with the same material and the same state of the furnace sample during nitriding production. After nitriding, the hardness and nitride layer depth of the sample shall be tested. According to the inspection standard of nitrided parts GB11354-1989, For critical parts, brittle and nitrided layer microstructure inspection shall be carried out after nitriding. The surface nitride hardness of the workpiece measured by the Leeb hardness tester shall be appropriately corrected according to the surface value of the furnace sample. (2) Since the nitrided part basically requires the tooth surface to be nitrided to improve the wear resistance of the used surface, when the hardness of the tooth surface is nitrided, the modulus is less than 4, and the hardness cannot be directly detected by using a Leeb hardness tester to avoid the tooth. The surface is too small to affect the hardness detection accuracy, and the hardness can be detected in other parts with similar tooth surfaces. Makeup Mirror With Lights,Mirror With Led Lights,Light For The Cosmetic Mirror,Mirror With Bathroom Led Light NINGBO EASTKEY ILLUMINATE APPLIANCE CO.,LTD , https://www.eastkeylighting.com
Test conditions: the workpiece and the sample are ion nitriding; the same sample and ring gear material is used, and the same quenching and tempering process and nitriding process are adopted, the quenching and tempering hardness is 270-280HBW, and the furnace sample and workpiece It is the same furnace nitriding; the micro hardness tester adopts the desktop HX-80A, the selected load is 2N, 10N; the portable Leeb hardness tester TH140, impact device. 
Figure 2 hardness gradient curve