The Research On Detection Error In The Leeb Hardness Testing Of Cast Iron And Nitrided Parts

For the many advantages, leeb hardness tester is widely used in the detection. But wefound that the detection values have error in the leeb hardness testing of cast iron and nitridedparts. We tested the hardness of grey cast iron, nodular cast iron, alloy structural steel andnitriding sample. At the same time, through metallographic analysis, hardness test andhardness gradient testing, we studied the base structure of metal material and surfacecharacteristics of nitriding layer.From the angles of macro and micro revealed the leebhardness test error, discuss the improvements. Thesis’s main research results are as follows:The organization inhomogeneity caused random error of iron hardness testing. Thephysical properties and forms of graphite in hardness test indentation caused error of ironhardness testing. We can change the leeb hardness tester’s hardware parameters, such asincreasing the drift weight and impact energy, increasing the drift diameter or using hammerbrinell hardness, make the test point more representative, to lower the organization inequalityand the impact of graphite, reduce testing random error.Because of the hardness of nitrided layer gradient changes, so Leeb hardness measurement is belowthe surface hardness, the test results is low. Matrix hardness and case depth impact Leeb hardnessmeasurement, when test the surface hardness of the nitride parts, resulting in a "breakdown andbottom effect", the test results is low. We can change the leeb hardness tester’s hardwareparameters, such as reduce the drift weight and impact energy, to reduce the indentation depth,reducing the hardness gradient and infiltration depth of adverse effects or using portableultrasound hardness, to solution surface hardness testing of the nitriding parts.