The use of fractal analysis to assess the influence of electrospark alloying on the durability indicators of hydraulic hammer parts

Abstract

Abstract. Statement of the problem. In order to increase the wear resistance and fatigue strength of the material of hydraulic hammer parts, it is not always advisable to change the traditional technology of manufacturing the part and, in particular, the methods of its heat treatment. Different types of finishing are applied only specifically to the given product. In some cases, it is worth applying surface strengthening of the product. Purpose and problem statement. The purpose of the work is to evaluate the impact of electrospark alloying on the durability indicators of hydraulic hammer parts. In order to achieve the set goal, it is necessary to: develop modes of electrospark alloying; conduct an analysis of the location of damage zones and their nature on parts strengthened by electrospark alloying, identical to those observed on tested parts manufactured without additional strengthening and with the use of LTO; Apply fractal analysis to evaluate the impact of electrospark alloying on the durability indicators of hydraulic hammer parts. Research material and methods. All details were strengthened by electrospark alloying with tungsten. The power of the processing current was 1 kW. The peak, in addition to strengthening with tungsten, was additionally processed by electrospark alloying with chromium at a current of 1.5 kW. The surfaces processed by electrospark alloying were ground to obtain the roughness of the strengthened surfaces of parts R and 04–08. Experimental results and their discussion. During the micro-examination of areas strengthened by electrospark alloying, which are outside the load zone during the test, it was established that the areas strengthened by electrospark alloying on the body and sleeve have a thickness of 10–40 μm and a hardness of Н V 600–650. On the strikers, the initial thickness of the hardened layer is 20 μm with a hardness of НV 600–650. The strengthened zones in the cross-section have the appearance of arc-shaped, embedded surface layers of metal parts, phases. There are no structural changes under this zone in the main metal. Conclusions. The results of tests of parts strengthened by electrospark alloying show that the wear resistance of the parts is increased by 1.3 times compared to the original state of the parts. Fractal models were obtained, which can be interpreted as a knowledge base for monitoring the strength indicators of the striker body, which allow monitoring its residual resource during operation. It was established that the strength indicators increase when the fractal dimension of the sorbite component increases, since it has better strength indicators compared to the original ferrite-pearlite structure. Indicators of pairwise correlation coefficients of the obtained models are fixed in the interval of values 0.6779...0.9254.