ДОСЛІДЖЕННЯ ВПЛИВУ ПОКРИТТІВ І ТЕХНОЛОГІЧНИХ МЕТОДІВ ВИГОТОВЛЕННЯ НАПРЯМНИХ ЕЛЕМЕНТІВ НА ЇХ ЗНОСОСТІЙКІСТЬ

Abstract

The matter of the experimental studies of the effect of coatings and technological methods of manufacturing guide elements of universal prefabricated readjustable tooling on their wear resistance are presented. The coatings investigated were made of VK15 carbide powder, which were applied by detonation spraying, and a titanium nitride-based coating produced by condensation with ion bombardment, as well as the surface hardening of guide elements by diamond burnishing for various steels: 20V, 12KhN3A, 40Kh, 38KhMYuA-B and others.During the process of diamond smoothing the roughness improves by 2 - 3 classes and the very nature of the roughness changes: a surface microrelief is created with rounded peaks and valleys instead of microroughness with sharp peaks and valleys, which are characteristic of surfaces after grinding. In this case the bearing surface of the samples increases essentially, and their running-in is accelerated. According to the results of tests under a load of 50, 75 and 100 kgf, a graph of the dependence of wear on the specific pressure was built and it was found that the wear of samples after burnishing decreases by 25 ... 40% compared to polished and at a load of 20 kgf/cm, respectively, is for steel 20 ... 2.7 and 1.9 μm, for steel 12XN3A – 2.3 and 1.6 μm, for steel 40X – 1.8 and 1.3 μm and for steel 38XMYUA – 1.4 and 0.8 μm.With increasing the load the wear of the ground specimens increases sharply, and for the flattened specimens this process is much slower. Based on the test results, graphs of the wear rate were plotted depending on the test duration, as well as for wear in relation to the number of cycles. According to the test results, it was found that steel 38KhMYuA has less wear, which is associated with its high hardness and insignificant tendency to metal seizure. Based on the research results, it was found that different methods of processing parts (previous) grinding and diamond burnishing have different wear. It has been found that diamond burnishing is a very effective surface hardening process.As a result of the tests carried out, it was found that the best performance in testing for wear resistance obtained for a column with TiN coating, the thickness of which does not exceed 0.1 μm, is 5 - 6 times less than the wear resistance of columns with a hard-alloy coating. For the system of directly changeable dies, a pair is recommended, which includes a guide column with a detonation coating VK15 and a holder (sleeve) with a CIB coating based on TiN, since these coatings showed high performance properties and had practically no wear.