Study of hardness and morphology of carbide coatings obtained on complex shaped steel items by electro-spark alloying

The work investigated the possibility of forming carbide coatings by electrospark alloying on steel products of complex shape. It has been established that electrospark alloying at an AC current of 1.0 to 4.5 A makes it possible to form coatings of hard carbide alloy VK6 and T15K6 characterized by microhardness up to 11.5 GPa and by hardness HRA 86.6 and 81.5 with the nitial hardness of the steel product HRA 80.3.

Multi-objective optimization of green powder-mixed electrical discharge machining of tungsten carbide alloy

Machining of difficult-to-machine materials produces huge amount of slurry and harmful aerosol concentration in the atmosphere, which are investigated in this work. In this study, an integrated framework was designed for the multi-response parametric optimization of powder-mixed electrical discharge machining of tungsten carbide alloy keeping into account both manufacturing and environmental aspects. Experiments were conducted using Taguchi L27 orthogonal array (OA), and process optimization was achieved using grey, grey-fuzzy, and grey-adaptive neuro fuzzy inference system–integrated approach. The multi-objective optimization techniques provide optimal parameter settings, i.e. medium pulse-on time (50 µs), low dielectric level (40 mm), medium current intensity (6 A), and high flushing pressure (0.6 kg/cm2). Results conclude that medium input discharge energies (pulse-on time and current intensity) are optimal for machining difficult-to-machine materials to produce low aerosol concentration. The comparison between the grades was performed to show the effectiveness of optimization approaches relative to each other. Finally, confirmation experiments were also conducted to indicate the effectiveness of the adopted optimization approach.

Stress Analysis of Forging Dies for Inverse Extrusion

This study intended to investigate the longitudinal crack on the tungsten carbide alloy die core that caused by the influence of receiving the hoop tensile stress in the process of inverse extrusion. Therefore, the shrink fit is adopted to design the die core and stress ring, and assemble the die case, in order to yield the hoop compressive stress in advance, which can be used to resist the tensile hoop stress yielded from the forging process. It also applied the FEM simulation software and Taguchi Method L9(34) in this study to simulate various combinations of different shrink fits, in order to obtain the best combination of die. Moreover, it focused on the compressive strength of material characteristics for the tungsten carbide alloy steel die core, and properly adjusted the shrink fit to prevent an early crack on the die core that caused by the hoop compressive stress in advance, in order to achieve the best result.

A Study On The Metal Carbide Composite Diffusion Bonding For Mechanical Seal

Mechanical Seal use highly efficient alternative water having a great quantity of an aqueous solution and has an advantage no corrosion brine. Metal Carbide composites have been investigated as potential materials for high temperature structural applications and for application in the processing industry. The existing Mechanical seal material is a highly expensive carbide alloy, and it is difficult to take a price advantage. Therefore the study of replacing body area with inexpensive steel material excluding O-ring and contact area which demands high characteristics is needed. The development of WC-Ni base carbide alloy optimal bonding composition technique was accomplished in this study. To check out the influence of bonding temperature and time, bonding characteristics of sintering temperature was experimented. The bonding statuses of this test specimen were excellent. The hardness of specimen and bonding rate were measured using ultrasound equipment. In this work, Powder of WC (involved VC, Cr), Co and Mo2C mixed by attrition milling for 24hours. Nanostructured WC-27.6wt.%Ni-1.5wt.%Si-0.11wt.%VC-1.1wt.%B4C composite were fabricated at 1190°C by high temperature vacuum furnace. To check out the influence of bonding temperature and time, bonding characteristics of sintering temperature was experimented. Its relative density was about 99.7%. The mechanical properties (hardness and fracture toughness) were 87.2 HRA and 4.2 M·Pam1/2, respectively. The bonding status of this test specimen was excellent and the thickness of bonding layer was 20 ~30§ at 1050 and 1060°C bonding temperature.