Technology And Theory Researche On Chrome-Plating Of Transmission System Component Of Helicopter Z8

This thesis is mainly to study the technology and theory of chrome-plating for the transmission system components of helicopter Z8 in order to meet the requirements of corrosion-resistance, wear-resistance and lubricating of the system. The technology, parameters, formulation, reaction principle and plating quality of chrome-plating are studied for parts with different materials (including hard chromium plating of aluminum alloy, chromium plating of steel base material, porous chromium plating of Chrome-Molybdenum cast iron expansion ring) of the transmission system. The chromium plating waste water treatment technology is also discussed in the paper.Firstly, the theoretical feasibility of using chrome-plating to solve the problem of corrosion-resistance, wear-resistance and lubricating for the parts of transmission system of helicopter engine which are made of cast iron, Alloy steel and the aluminum alloy is discussed. Four kinds of chrome-plating coupon with three different materials including cylindrical alloy steel coupon, and sheet alloy steel coupon, porous Chrome-Molybdenum cast iron expansion ring and 7075 aluminum alloy coupon are made by using two kinds of plating formulation, three groups of temperature and current intensity parameters. Then, the microstructure, composition, hardness, thickness, corrosion resisting property and hydrogen brittleness etc. of the coupons' plating layer are studied and tested in detail by such methods as X-ray, SEM etc. Finally, combined with corresponding theory, the effect of chromium-plating technology, formulation and parameters on the chrome- plating film quality and performance is studied and the best technological parameter range and formulation have been found.Through the tests, this thesis has generated conclusions as follows:1. Under the current intensity of 35A/dm², and at temperature of 45℃, when the time intervals are equal, the chromium plated films on steel and aluminum alloy bases are thin, the porosity is larger, the films are grey white, the corrosion resisting property is bad and the hardness is low. The crystal structure of the film is dense hexahedron. The plating film is obviously separated from the base metal. The deep plating ability for expansion ring chrome-plating is bad, the hardness of the film is low and the wear and corrosion-resisting is not well.2. Under the current intensity of 55A/dm², and at 70℃, when the time intervals are equal, the chromium plated films on steel and aluminum alloy bases are thicker, the porosity is smaller, the films are dim, the corrosion resisting property is bad and the hardness is higher. The crystal structure of the film is not even and unstable. The deep plating ability for expansion ring chrome-plating is not well, the hardness of the film is unstable and the lubricating and corrosion- resisting is better but the wear resisting is not well.3. Under the current intensity of 45～50A/dm², and at 55～60℃, when the time intervals are equal, the chromium plated films on three kinds material bases are thicker, the porosity is smaller, the films are shining, the corrosion-resisting property is good and the hardness is high. The crystal structure of the film is body-centered cube construction and very stable. At 40±5A/dm², 56±2℃, the films are shining, harder, good wear-resisting and good lubricating property. At 45-50A/dm², 53-55℃, the chromium plated film on aluminum alloy base is best, the hardness is highest and the bonding force is strong.4. The best chrome-plating composition is at CrO₃: 200～250g/L, Cr³⁺: 3～5g/L, H₂SO₄: 2.0～2.5g/L, CrO₃/H₂SO₄: 95～102.