Basic Experimental Research On Crack-free Hard Chromium Electroplating

Chrome plating endows the metal material with excellent corrosion resistance, wear resistance and low friction coefficient. Functional chromium plating can more make the material surface to obtain a variety of special properties, and make it become the new functional material. So, as a surface treatment technology, chromium plating has been widely used in surface protection of key mechanical parts in aerospace. Aircraft landing gear material — 300 M high strength steel has low wear resistance and corrosion resistance, so it needed to have an electroplated layer of chrome on the surface when they are used. However, the traditional electroplated chromium layer inevitably had the perfoliate micro crack, which affected the corrosion resistance of chromium plating parts; and after electroplating, the surface showed a tensile stress state, which can impair the properties of material. Therefore, it needs to improve the process.In order to eliminate micro crack chrome plating layer fundamentally and improve corrosion resistance of coatings, the basic research will focus on crack-free hard chromium pulse electroplating method, which was based on abrasion-assisted electroplating technology in improving coatings properties. The following work has been done:1. An experimental system of crack-free hard chromium electroplating has been structured, including the improvement and optimization of the electroplating process system. In order to obtain a uniform electric field on the surface of the cathode, the auxiliary cathode was adopted to eliminate the concentration phenomenon of electric field line. The main works are as follows: simulate and optimize the shape of the auxiliary cathode and the process chamfer of cathode, analyze the different dimensions of auxiliary cathode and process chamfer on the law electric field, and do the simulation results comparison test finally.2. Experimental research of crack-free chromium electroplating was carried out on the 300 M steel substrate. Influences of process parameters on microstructure, stress state, tensile strength corrosion resistance, and hardness of the coatings have been studied, summarized and evaluated.3. A new crack-free hard chromium electroplating machine have been developed, including test platform, motion system, the rotary sealing structure, the portable work piece clamping device, compressing tightly and conductive mechanism, electroplating unit, plating solution circulation system and electric control system.