Aspects of Applying Hard Chromium Coatings on the Inner Surfaces of Components for Hydraulic Drives with Hydrostatic Guideways

Abstract

We considered the processes of chromium plating the inner surfaces of the components of cylinders with hydrostatic guideways. We demonstrated the various aspects of the chromium plating process – the limitations placed on the machinery depending on the dimensions of the parts to be plated and the unevenness of the deposition rate of chromium along the length of the part. We developed a diagram of an installation for the application of a hard chromium coating on inner surfaces, which includes a cathode, an anode, a tank, and a pipeline. The distinctive features of the installation are the method of supplying the electrolyte at an angle to the horizontal, which allows us to supply the electrolyte through a turbulent flow swirling along a helical path, and the use of a chromium-plated installation casing. We studied various modes for applying a hard chromium coating on the inner surfaces of a hydraulic cylinder. As a result, we determined the optimal composition of the chromium electrolyte – the ratio of chromic anhydride and sulfuric acid – which is 10:1, respectively, and experimentally selected deposition modes. Chromium coatings obtained through the use of the concentrated electrolyte, which we developed, and the chromium plating method have 5...20% greater hardness and a 10...30-times reduction in porosity with the formation of a shiny, lumpy sludge, which corresponds to corrosion-resistant and wear-resistant coatings needed to manufacture hydraulic drives with highly efficient hydrostatic guideways.

Research on Chrome Plating Quality of the Internal Surfaces in the Hydraulic Drives with Hydrostatic Guideways

“…A study of the chrome coating was carried out, for this we cut out sectors from the samples, carried out their sample preparation, measured the hardness and took pictures under a microscope, measured the hardness and thickness of the chrome coating. The obtained measurement results: deviation from roundness, deviation from straightness, coating hardness, coating thickness -correspond to the specified technical requirements, the proposed construction of the installation for applying chrome coating to the inner surfaces and the electrolyte composition, selected earlier [15], are applicable for chrome plating of the inner surfaces.…”

“…A chrome coating was applied to the inner diameter of the pipes in the developed installation. The design of the installation for applying chrome plating on internal surfaces is shown in Figure 2 and is described in detail in a previously published article by the authors [15]. The installation is equipped with a system of ecological protection of the environment from harmful vapors of the electrolytic solution [16].…”

“…Based on this, the outer surface of the piston rod and the inner surface of the cylinder should be chrome-plated. Previously, a technology for applying chrome plating to the outer surfaces [12,13,14] and an installation for applying chrome plating to the inner surfaces of hydraulic cylinders [15] were developed.…”