DETERMINATION OF THE THICKNESS OF THE COMPONENTS OF A DOUBLE-LAYER NICKEL-CHROMIUM COATING BY MAGNETIC PONDEROMOTIVE METHOD WITH UNILATERAL ACCESS TO THE CONTROLLED SURFACE

The application of thick-layer nickel (up to 700 μm) and chromium (up to 200 μm) coatings has been widely used to give the combustion chamber of a liquid-propellant rocket engine the required operational properties. The main parameter that determines the ability of a coating to fulfill its function is its thickness and uniformity of its distribution. The main problem of current nondestructive methods for determining the thickness of coatings under consideration is that they can be used only at the stage of production of rocket engineering products, when there is an access to the product from the side of the inner wall of the combustion chamber before and after applying a chromium coating to the nickel sublayer. However, when an already finished product arrives at subsequent stages of assembly to another enterprise, there is often a need of incoming control of the thicknesses of coatings from nickel and chromium. In this case, it is not possible to apply existing control techniques to a finished product, or the use of these techniques leads to unacceptable errors in the results of measurements. The goal of the research was to develop a technique for nondestructive determination of the thickness of each component of the two-layer nickel-chromium coating by the magnetic ponderomotive method under conditions of unilateral access to the finished product from the side of the chromium coating.

A new technique for nondestructive determination of the thicknesses of nickel and chromium coatings of the double-layer structure on a finished product without a priori data on the properties or thicknesses of these coatings or a product in general is proposed using a magnetic ponderomotive method.

This newly developed technique is implemented in the thickness gauge TEP-XN1 of double-layer nickel- chromium coatings, which is successfully used by enterprises of the rocket and space industry of the Russian Federation.

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