Painting Skills: Introduction to Electroplating Process of Domestic Sliding Bearing Antifriction Layer

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Painting Skills: Introduction to Electroplating Process of Domestic Sliding Bearing Antifriction Layer

Source: Bearing network time: 2018-03-31
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Brief introduction of sliding bearing anti-friction layer plating process. The domestic research and application of anti-friction alloy coating started late. In 1960, the first research and development of Wuhan Data Protection Research Institute and Hailing Top Parts Factory and the production of brush-plated tin-tin alloy have been used. Speedboat engine plating. In the mid-1970s; Shanghai Alloy Bearing Factory and Shanghai East Shipyard made a more detailed discussion on the electroplating of copper and tin alloys. In 1985; Harbin Institute of Technology Electrochemical Teaching and Research Institute and China National Shipbuilding Corporation The Six Sixth Factory jointly discussed the process of electroplating lead-tin-copper ternary alloy anti-friction layer on lead bronze sliding bearings; it has been used in production. In 1989, Dusanka Radoric announced that "hydrogen bismuth in fluoroborate plating solution (for one Hydroquinone) is an additive lead-tin alloy electroplating paper. At the end of the tenth century; Fanjiahua and Jiang Zhidong of Nantong Bearing Factory; Wuhan Institute of Data Protection, Zeng Liangyu, Yang Xiangui, Wang Huiwen; Guangxi Guilin Internal Combustion Engine Parts Factory Qin Shengyi; Qishuyan Motorcycle Vehicle Technology Research Institute Xue Bosheng簦The process of electroplating of anti-friction layer has been studied in different degrees from different aspects; The further improvement in the application has laid a certain foundation. 3 The problem is that the lead-tin-copper ternary alloy anti-friction coating electroplating process of our factory is the first in China; for many years, we have supplied a lot of bearing bushes for our mainframe parts shopping malls. These years; our factory bearing products order quantity It has risen year by year; and some bearing products have entered the world market. We are fortunate to export. This fully reflects the strong strength of our factory's bearing products in the fierce shopping mall competition. From 1989 to 1991; after hard work and repetition The experiment has fundamentally dealt with the problem of the squeezing of the bearing layer of the bearing bush, the defect of the peeling 簦 adhesion strength, eliminating the serious serious corrosion problem of the matrix, overcoming the batch wall thickness difference; improving the process ability, the waste loss rate has always been Very low; the rate of qualified products for one inspection has improved year by year. However, the defects of rough coating, nodules, spots, pits, and airflow stripes are still on the rise; sometimes the cathode current density (DK) does not reach the scale of the process scale. The above-mentioned shortcomings of the friction-reducing coating directly affect the quality of the bearing products. With the continuous modification of the main engine model, the localization and import of imported models The competition is becoming more and more fierce; the quality demand of the bearing products is getting higher and higher. The competition in the mall is basically the quality competition of the F product. Under the increasing demand for the quality indicators of the products; we are facing the improvement of the bushing plating process and further improvement of the bearing bush. The new topic of product quality is a serious challenge. 4 Factors affecting the quality of the anti-friction coating of the bearing bushes 4. The lead formula of the lead-tin-copper ternary alloy anti-friction layer plating solution and the process parameters are announced in the literature. The composition content and process parameters are summarized as follows: Pb2+ (participated by Pb(BF4)2): 80-333g/ι, Sn2+ (part of Sn(BF4)2): 5～33. 3g/ι, Cu2+ (with Cu (BF4) 2 way participation): 2 ~ 11g / ι, HBF4 (free): 40 ~ 300g / ι, H3BO3 (free): 15 ~ 40g / ι, stabilizer: 2 ~ 12g / ι, additives: 0. ~5g / ι, cathode current density (DK): 1 ~ 8A / dm2, temperature (T): 15 ~ 30 ° C, time (t): 15 ~ 35min, coating thickness (δ): 15 ~ 30μm, anode composition: PbSn8～11.4. 2 The factors affecting the quality of the anti-friction coating can be seen from the above formula; regardless of the F component content, the F process parameters; The scale is too wide, which is the customary production demand; it is necessary to further optimize the quality; before the optimization experiment, the necessary analysis of the factors affecting the quality of the anti-friction coating is carried out; to determine the feasible range of each factor in the orthogonal experiment. 2.1 The main salt ion concentration affects the main salt ions in the plating solution as Pb2+, Sn2+, Cu2+. The content of Sn2+ and Cu2+ can be adjusted according to the percentage of Sn and Cu in the alloy coating. It can satisfy the user's demand for coating composition. Therefore, for the main salt ion; only the influence of the Pb2+ content in the plating solution on the quality of the coating is reviewed. Pb2+ in the plating solution is the primary component of the alloy coating; the reported content in the literature is 80-333g/ι. High; it is allowed to use higher cathode current density; the stacking speed is fast, but the enthalpy can be reduced; the loss is large. If the concentration is lower, the scatter is better; but the stacking speed is slower. If the content is too low, the plating is too low. The liquid concentration polarization is too large; the current does not rise; the plating layer is easy to exhibit the airflow stripe defect and the pyramidal microscopic metallographic layout; the visual representation is that the coating is rough. If the content is too high, on the one hand The loss of plating solution is increased; the cost is added, and on the other hand, the boric acid (H3BO3) and the additive are precipitated when the temperature is low; then the coating is rough. The FDK is suitable to rise to the upper limit of the process rule; and the coating is crystallized in detail. When the temperature drops below 15 °C; the plating solution should be free of boric acid and additive precipitation. 4.2.2 Free fluoroboric acid (HBF4) concentration affects its primary role in promoting normal anode dissolution, avoiding divalent tin (Sn2+) Oxidation and hydrolysis of primary ions (Pb2+, Sn2+, Cu2+); progress in plating stability, improved conductivity and entanglement, refinement crystallization. The reported content scale is 40-300g/ι. When the free fluoroboric acid content is too low It has a low hydrogen ion (H+) concentration; the following hydrolysis reaction may occur in the plating solution, Pb2++2H2O is less than == greater than Pb(OH)2↓+2H+Sn2++2H2O is less than == greater than Sn(OH) 2↓+2H+Cu2++2H2O is less than == is greater than Cu(OH)2↓+2H+. They all form hydroxide deposits and are suspended in the plating solution. When plating, they adhere to the surface of the substrate or are mixed in the coating. ; the bonding force between the plating layer and the substrate is reduced; and the plating layer is brittle, rough, and spotted; then The layer wear resistance and fatigue strength 簦 function is significantly reduced. When the free fluoroboric acid content in the plating solution is too high; at the high current density of the plating part; that is, the bearing bush has burrs local or sharp edges, and the end face has hydrogen gas. The result F is the appearance of airflow streaks and pinhole defects on the bearing layer of the bearing. Together; the edge effect and the tip discharge make the deposition at high current density too fast; the main salt ions in the plating solution can not be compensated; that is, the surface dispersion or nucleation manipulation changes Mass transfer in the liquid phase; concentration polarization increases so that the inner and outer surfaces of the bearing shell (cathode) have the following electrochemical side effects: 2H++2e is less than == greater than H2↑ can be seen from the above reaction; when hydrogen ions (H+ When the concentration (ie, the corresponding free fluoroboric acid concentration) increases; the equilibrium moves to the right; promotes the formation of hydrogen (H2). The hydrogen evolution results not only cause the coating to exhibit airflow streaks and pinhole defects; but also because of the initial ecological hydrogen (H Hydrogen radicals impregnate the interior of the coating to form a metal hydride and cause lattice distortion and thread misalignment. If scanning electron microscopy (SEM) is used to investigate the microscopic trace of the coating; it can be found that the crystal has a large pyramid layout; F is the matte plating layer on the other hand;. Metal hydrides F constituting unstable substances; baked differentiate when heated to release the check hydrogen (H2) was then bubbled attack plating appearance.
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