Surface Hardening of 40KH Steel by Electric-Spark Alloying

We substantiate the possibility of application of the method of electric-spark alloying of the surface layers of 40Kh steel by electrodes made of Т15К6 and VK8 hard alloys for the purposes of hardening of the working surfaces of elements of the drilling equipment. It is shown that, as a result of local electric discharges between the cathode and the anode, the surface layers can be alloyed with Co, W, and Ti down to a depth of 10–20 μm. It is established that, in order to guarantee the serviceability of surfacehardened elements under severe operating conditions, it is necessary to get a sufficiently high microhardness of the surface layer, optimize the sizes and density of oxides in this layer, and to minimize the residual tensile stresses responsible for cracking. To get the best combinations of these characteristics, we optimize the technological parameters of electric-spark alloying.