Formation of vanadium carbide with the plasma electrolytic saturation method (PES) and comparison with Thermo Reactive diffusion method (TRD)

<p>One of the most important hardening methods of tool steel is the use of carbide coatings, in which during this process, vanadium diffuses in the specimen’s surface and reacts with carbon. During the Plasma Electrolytic Saturation Process, the vanadium element diffuses with the help of plasma and increases up to around 1000 degrees as a result of the temperature, providing conditions for the creation of vanadium carbide. On the other hand, the TRD method during which the specimen is placed inside a salt bath containing the vanadium for a long period of time and the vanadium carbide coating is formed. In this paper, an attempt is made to study the formed coating with the method of plasma electrolytic saturation in addition to comparing the coatings formed by these two methods and obtain some results like: vanadium carbide that created with TRD is purer than PES but that is thinner than plasma method, hardness of coating that created with TRD is about 2500vikers but in TRD is 1100vikers finally. In some PES samples the temperature increase slowly and the maximum temperature is about 120^oC, in this condition, coating is non diffusion. Hardness of PES coating is about 1100vikers so we can use that in industrial molds.</p>

Effects of Technological Conditions and Substrate Material on TD Coatings

Thermal diffussion (TD) is a method of coating steels to improve the service life of materials and tools. With this process, high hardness of vanadium carbide coating is formed on the surface of materialsso that its wear, bite, corrosion resistance can be greatly improved. Since thereare still several problems remaining to be solved, this technology is still not widely used in our country and that limit the popularity of the salt bath technology. In this paper, these problems and their causes are discussed based on experiments, and several solutions are presented to hopefully provide suggestions for industrial production.

THE SURFACE AND INTERFACE PROPERTIES OF VANADIUM CARBIDE COATING PREPARED BY THERMAL DIFFUSION PROCESS

Vanadium carbide (VC) coating is prepared with Thermal Diffusion (TD) method in the salt bath, and its surface-interface microstructures and energy spectrums were observed with Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS), respectively, and the distributions of C , V , Cr , Si , Fe , and Mo in VC coating interface are analyzed. Its interfacial and bonding methods are discussed, and the bonding micromechanism of VC coating in its bonding interface by TD process is analyzed. The experimental results show that the structure of coating surface by TD is single-phase, that is composed of V and C elements, and no other elements, the chemical elements such as V , Cr , C Si , Fe , Mo are the grade distributed in its bonding interface; its bonding method is metallurgical status; microhardness of coating-substrate is the grade distribution, which is direct ratio with the V distribution, microhardness of the coating surface is 3050–3200 HV, and the effect of TD process on roughness of cold-working die surface is little.

Prediction of Layer Thickness in Molten Borax Bath with Genetic Evolutionary Programming

In this study, the vanadium carbide coating in molten borax bath process is modeled by evolutionary genetic programming (GEP) with bath composition (borax percentage, ferro vanadium (Fe-V) percentage, boric acid percentage), bath temperature, immersion time, and layer thickness data. Five inputs and one output data exist in the model. The percentage of borax, Fe-V, and boric acid, temperature, and immersion time parameters are used as input data and the layer thickness value is used as output data. For selected bath components, immersion time, and temperature variables, the layer thicknesses are derived from the mathematical expression. The results of the mathematical expressions are compared to that of experimental data; it is determined that the derived mathematical expression has an accuracy of 89%.