Cu-Sn-Fe Coated Powder
Traditional oil-bearing raw materials by mechanical mixing iron and bronze powder, inevitably producing ingredient and microstructure segregation, resulting in uneven performance and the hard phase, leading to increased running noise bearing and shorten life. In order to overcome the traditional mechanical mixing powder disadvantage fundamentally effective solution to the chemical composition of oil-bearing products and tissue segregation problem. Taking iron as the matrix, the use of chemical plating and displacement plating two methods were implemented in the quantitative iron powder coated 20% Cu + 2% Sn, prepared by coating integrated and compact, with strong, excellent oxidation resistance of Cu / Sn double metal coated iron powder, and then the coated powder obtained by the above two methods is alloyed by vacuum heat treatment, successfully developed the Cu-Sn alloy-coated iron powder. X-ray diffraction (XRD) and chemical titration test means and methods of cladding elements of the qualitative and quantitative analysis; scanning electron microscopy (SEM) and optical microscope observation of the fracture surface and surface morphology of the powder, coating the coating effect is determined. By orthogonal experiment to study the influence of various factors on the bath coating quality, optimize the process parameters; by a kinetic experiment, the initial primary concentration, concentration of complexing agent, reducing agent concentration, temperature and pH on rate of reaction. Studies have shown that: the replacement Preparation Sn / Cu / Fe composite powder tin plating is the best: SnCl_2 -5g / L, citric acid 30g / L, pH = 1.2, temperature 85 ~ 90 ℃. Kinetic experiments showed that stannous chloride bath, the replacement rate is significantly affected by temperature and pH of the bath. Replacement rate increases with the bath temperature increases with increasing pH value will decrease. Replacement of the system as a reaction to the chemical aspects of the control of the kinetic data obey laws of a reaction rate. Displacement reaction Arrhenius equation: ln k = -9.64 / T + 26, the activation energy E a = 80.1 kJ / mol. Experimental results show that the stability of the bath, [SnCl_2] = 5g / L, pH = 1.2, and when you add a tin stabilizer, stability of the bath is best. Preparation of chemical plating Cu / Sn / Fe composite powder of copper plating process is best: CuSO_4-12g / L, HCHO-12ml / L, EDTA · 2Na-25g / L, the bath pH = 13, temperature -45 ℃ . Kinetic experiments show that the reaction rate is significantly affected by the initial copper concentration, the concentration of complexing agent, reducing agent concentration, bath temperature and pH values. The reaction rate increased with the bath temperature, the initial copper concentration, reducing agent concentration and an increase in pH value increases with the increase of complexing agent concentration increases. Composite powder prepared by the above two methods alloying treatment, XRD experiments show that: alloying Cu / Sn coating layer system there are two mechanisms, namely melting - dissolution - precipitation mechanism and diffusion - solution mechanism. And with the heat treatment temperature, holding time, the higher the degree of the clad alloy. Heat treatment temperature is 600 ℃, heat 1 hour, fully alloyed cladding layer formed Cu_ (81) S_ (n2) 2, Cu_ (5.6) Sn and Cu_ (20) Sn_6 three alloys phase.
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