Research On Microstructure And Properties Of The RE-chromevanadium Multicomponent Layers On Hot Work Die Steel H13

Mold is a very important process equipment in modern industrial production. The importance of mold is self-evident.With the rapid development of the mold industry, production requirements of surface properties of the mold are also increasing. As an advanced surface modification technology on die, TD(Thermal Diffusion Carbide Coating Process) treatment can largely improve overall performance of the mold surface to extend its life. And because of the simple device, easy to operate, environment-friendly, low production cost, it has been widely used in recent years. For integrating advantages of vanadizing and chromizing to get excellent overall performance coatings, this paper adopts TD salt bath chromvanadizing as the experimental research method.Rare earth elements has special electronic structure and lively nature. It can strengthen bath activity and promote metal infiltration in the heat treatment. And Our country’s rare earth reserves are abundant. In order to improve coating performance and make resource advantages into economic advantages of technology, the rare earth elements have been introduced into TD chromvanadizing process. In this paper, We studied microstructure and properties of the RE-chromevanadium multicomponent layers and analyzed the role of rare earth on the performance of chromvanadizing layers.By using optical microscope, micro hardness tester, three-dimensional scanners, scanning electron microscopy(SEM), X-ray diffraction(XRD), energy dispersive spectroscopy(EDS) and other equipment,we used RE-chromevanadium permeation on hot work die steel H13(4Cr5MoSiV1) and 45 steel and explored the optimum formula and process. Through observation of coating structure, analysis of phase composition, testing performance,it can summarize the impact of rare earth elements on the coating properties and analyze their causes. The forming theory of RE-chromevanadium multicomponent layers had been discussed from the thermodynamic and kinetic aspects. After experimental research and comprehensive analysis, the main conclusions were obtained as followed:1. The coating on two material is uniform, dense and smooth. The layer is mainly composed of Cr7C3, Cr23C6, VC three-phase composition. Chromium carbides are mainly in the outer coating and Vanadium carbides mainly in the inner layer.2. The optimum formulations and processes of TD RE-chromvanading treatment on H13 steel and 45 steel had been obtained. By using the formula of Na2B4O7 + NaF + 3% RE + several vanadium and chromium and 960 ℃ × 6hTD treatment, we can get optimum overall performance of RE-chromevanadium multicomponent layers. The surface coating thickness of H13 steel and 45 steel was, respectively, 5.61μm and 8.77μm; coating hardness was 2026HV0.05 and 2167HV0.05.3. Under the same kind of process, the addition of rare earth can increase the thickness and hardness of chromvanadizing layers. Wear resistance and high temperature oxidation resistance also has increased dramatically. Adding rare earth can also enhance coating layer and the substrate binding force to improve the value of the cladding.4. When chromvanadizing layers were etched in high temperature oxidation, oxide growed on the surface in the shape of columnar crystals. When it was oxidized more serious,the boules were more intensive and bigger. After high temperature oxidation, the growth of columnar oxide crystal is not obvious on RE-chromevanadium multicomponent layers.It had excellent oxidation resistance.