Study On Process And Properties Of Co/Ni60 Composite Coating Prepared By Laser Cladding

With the development of titanium alloys,due to its high specific strength and good comprehensive mechanical properties,it is widely used in aerospace,marine engineering,shipbuilding and other important fields,but due to its low surface hardness and other shortcomings,Surface modification is required to increase the range of applications.The B element can improve the texture of the coating,refine the grain of the coating,and improve the microstructure of the coating.In this paper,the Co-based coating and the Co-based/Ni60 composite coating with different B contents were prepared by laser cladding technology to improve the comprehensive performance of the titanium alloy.The process parameters were optimized,and the microstructure,microhardness,friction and wear test,electrochemical corrosion test,element distribution and phase composition of Co-based coating and Co-based/Ni60 composite coating were studied,and the comprehensive properties of the coating were analyzed.By setting nine orthogonal tests,the microhardness of the coating,the average friction and wear coefficient,and the average open circuit potential were used as indicators to optimize the laser cladding process parameters by principal component analysis and multiple linear regression analysis.Through the triangular cloud diagram,the optimal process parameters for the test were determined to be laser current 380 A,laser frequency 4 Hz,and laser pulse width 8 ms.The microhardness of Co-based/Ni60 composite coatings with different B contents was measured by Vickers microhardness tester.The friction and wear tests were carried out on the coatings using a friction and wear tester to verify the wear resistance of the coatings.The frictional force and friction and wear coefficient in the process,and the wear trajectory,wear 3D topography and wear track cross-section are analyzed by scanning electron microscopy to analyze the friction and wear mechanism of the coating,and compare the B-based coating with different B content.And the friction resistance of the Co-based/Ni60 composite coating.The results show that the hardness of the coating with 6% B content in the single layer coating is the highest,but the friction grinding loss is the largest due to the high crack content.The Co-based/Ni60 composite coating with different B content is more resistant than the single-layer Co-based coating.The wearability is good,and the hardness decreases after the Ni60 is coated on the 6% B content of the Co-based coating,but the wear resistance is greatly improved.The corrosion resistance of the coating with different B content was tested by electrochemical workstation.The corrosive medium was 3.5wt% Na Cl,the three-electrode test method was adopted,the reference electrode was made of platinum electrode,and the auxiliary electrode was made of saturated potassium chloride.Corrosion resistance test of the coating was carried out by an electrochemical workstation,and the self-corrosion tendency,corrosion potential and corrosion current of the sample were calculated by data.The results show that the corrosion resistance of Co-based/Ni60 composite coating is stronger than that of single-layer Co-based coating.The corrosion resistance of Co-based/Ni60 composite coating with 6% B content is the best.The microstructure,element distribution and phase composition of the cladding layer with different B contents were observed by scanning electron microscope,X-ray diffractometer and optical microscope.The difference of B elements in the coating material was analyzed to make the microstructure of the coating.The law of change.The results show that the elemental transition distribution between the coatings indicates that the coating forms a good metallurgical bond with the matrix,and a certain amorphous component is formed in the coating.It is formed in the 6% B content of the Co-based coating.Ti B and other components increase the hardness of the coating.