Diamond-ECM Grinding of Sintered Hard Alloys of WC-Ni

Continuing the theme raised by the authors on the ISEM-2013 and related to the diamond - ECM grinding of ceramic-metal tungsten (DECMG) they discuss the results of the study of this method of machining of sintered alloys WC-Ni, as construction material. Difficulties arising during their DECMG machining and associated features of the structure and chemical links formed in the tungsten carbides are noted. The conditions to overcome these difficulties through the optimal combination of anodic dissolution and micro-cutting, manifestations of different effects, including the effect of the adsorption strength reduction, electro-capillary, ultrasonic and sound capillary effects and their synergy are shown. The main reactions of anodic dissolution of alloys in the electrolyte - an aqueous solution of Na2HPO4 and Na2CO3 with additives and regularities governing the functioning of the electrolyte in the gap are defined. The grinding using diamond cup wheels 12A2-45° bonded by the Cu-Al-Zn according the scheme of elastic frontal grinding DECMG with rotation of the work-piece is recommended to achieve the roughness Ra ≤ 0.63-0.32 mμ at the surface planes such as planes of disk supports for tests according to GOST 27034-86 (ISO 4506-79), or planes of washers for power thyristors and rectifiers having the area up to 2000 mm2. Limit conditions of zero-defect DECMG (no burn marks, no micro-cracks in the surface layers and in the grains of the alloy) are determined as following: grinding speed of 12-18 m/s; operating voltage of 3-4 V; the normal component of the grinding force 0.25-0.27 kN/cm2. Information about the regularities of anodic dissolution of alloys, the functioning of the electrolyte, modes and characteristics of DECMG with the end face of a cup grinding wheel can be useful for researchers and developers of physical, chemical and combined methods of machining.