Study On Preparation And Properties Of Coatings Based On Induction Cladding Remanufacturing

That remanufacturing technology can restore size and performance of critical parts,is one of the important means to improve the reliability and longevity of mechanical systems.In this paper,based on the cylinder liner of marine diesel engine,the Ni-based coating and Fe-based coating were prepared on the surface of HT 300 by ultrasonic frequency induction cladding.The following three problems were discussed:(1)The melt-solidify process of low melting point Ni-based alloy coating;the influence of heating time on porosity,microhardness and corrosion resistance;(2)The influence of welding flux and heating parameters on high melting point Fe-based alloy particles;(3)Microscopic morphology,phase composition,microhardness distribution,wear resistance and corrosion resistance of Ni-based coatings and Fe-based coatings.The sample was subjected to ultrasonic frequency induction cladding treatment by using a self-built experimental station.The microstructure,porosity,elemental composition distribution and phase composition of the coating were observed and analyzed by optical microscopy,scanning electron microscopy,energy dispersive spectroscopy and X-ray diffractometry.The Vickers microhardness tester was used to measure the hardness distribution of the coating section.The corrosion resistance of the coating was investigated by electrochemical corrosion test and immersion corrosion test.The friction coefficient and wear amount of the coating and the chrome-plated gray cast iron plate were tested by the reciprocating friction and wear tester independently developed by Dalian Maritime University to analyze the wear resistance of the coating.The experimental results show that:(1)In the process of cladding Ni-based coating on the surface of HT 300,when the heating time in the melting stage was 9s and the heating current was 20A,there was an element transition zone between the coating and the matrix to achieve metallurgical bonding.The microhardness changed in a gradient,and the porosity of the coating was lower under this parameter than in other parameters,and the corrosion resistance in the sulfuric acid solution was higher.(2)In the process of cladding the Fe-based coating on the surface of HT 300,the welding flux can effectively remove the oxide on the surface of the alloy particles and lower the melting point.By increasing the holding period,the oxidation time of the flux can be prolonged and the mutual fusion of Fe-based metal powders can be promoted.(3)The Ni,Cr and Si elements in the Ni-based coating can effectively improve the electrode potential of the coating and achieve the corrosion resistance of passivation protection,and the corrosion rate was much smaller than that of the matrix.However,the Fe-based coating and the matrix cannot form a dense passivation film during the etching process,and the etching solution penetrated the pores into the metal surface,so the corrosion rate of the Fe-based coating and the gray cast iron were similar.(4)In the process of friction and wear,the wear mechanism of Ni-based coating mainly manifested as abrasive wear and oxidative wear.The oxide adhesion of the wear surface was poor and easy to fall off but has lubricating effect,so the friction coefficient was smaller and the wear amount was bigger.The wear mechanism of the Fe-based coating was characterized by abrasive wear and oxidative wear.The oxide formed by the wear adhered firmly to the surface,but the shear force between the wear and the wearer was larger,so the friction coefficient was larger and the wear amount was smaller.