Study On Mechanism And Properties Of Multi-fields Coupled Deposited Ni-TiN Nanocoatings On The Surface Of Key Parts In Mud Pumps

As a significant part of the drilling equipment,the drilling mud pump is mainly used to transport high sediment content,high viscosity and corrosive drilling fluid during the drilling process,thus it is usually subjected to heavy load torque,high pressure erosion and corrosion of mud fluid,and hard particle wear for a long time.Therefore,the key parts of drilling mud pump such as cylinder liners,pistons,valves and crankshafts are prone to abrasion,leakage and corrosion.Thus it has become one of the key problems for improving the surface performances of the key parts in mud pumps.The metal based composite coating is a kind of composite materials which the deposited metal and the second phase strengthened particle act as the continuous phase and dispersed phase,respectively.One or more strengthening particles can be embedded in the metal coating to form a metal-based composite coating by using the electrodeposition method.The structure of the coating mainly consists of the reduced metal on the cathode surface and the second phase strengthened particles.The nanocoating is a kind of nanomaterials formed by the inclusion of nanometer second phase particles?i.e.SiC,TiN,Al₂O₃,etc.?in the matrix metals.There are a large number of second phase particles in nanocoatings,and these particles have some excellent properties which make the nanocoatings have some certain physical or chemical properties.The deposition of Ni-TiN nanocoatings with high microhardness,high strength,good wear resistance and corrosion resistance on the surface of key parts in mud pumps could significantly improve their surface comprehensive performance.However,TiN nanoparticles could not effectively dispersed in the bath in the preparation of Ni-TiN nanocoatings by using the ultrasonic or magnetic field with electrodeposition.This led to the result that TiN nanoparticles could not uniformly disperse in nanocoatings.Therefore,it was necessary to combine ultrasonic,magnetic and electric fields to fabricate Ni-TiN nanocoatings on the surface of key parts in mud pumps.The manufacture technology,surface morphology,microstructure and properties of Ni-TiN nanocoatings prepared by multi-fields coupling deposition were systematically studied,and then the plating parameters were also determined and optimized.In this paper,Ni-TiN nanocoating was chosen as the investigated object,and the combination of experimental research and theoretical analysis were applied to systematically study the surface morphology,microstructure,TiN nanoparticle composition,microhardness,wear resistance and corrosion resistance of the Ni-TiN nanocoatings deposited by multi-fields coupling electrodeposition.the orthogonal test method was used to optimize the process parameters of the Ni-TiN nanocoatings deposited by multi-fields coupling electrodeposition,and the wear mass of the Ni-TiN nanocoating was predicted by a BP neural network model.The effect of various process parameters on the TiN nanoparticle composition,microhardness,wear and corrosion amount of the Ni-TiN nanocoating was investigated to find a reasonable range of process parameters:the plating solution temperature of 50?,the addition of TiN nanoparticles of 7¹0 g/l,pH of 3⁵,cathode current density of 1.5².5 A/dm²,pulse duty ratio of 30⁵0%,ultrasonic power of 150²50 W,surfactant dosage of 90¹50 mg/l,magnetic field intensity of 0.4⁰.6 T,and the deposition time of 60 min.The orthogonal test method was used to optimize the process parameters of the Ni-TiN nanocoatings deposited by multi field coupling,and the optimum combination of process parameters were as follows:TiN nanoparticles concentration of 8 g/l,cathode current density of 2.5 A/dm²,pulse duty ratio of40%,ultrasonic power of 200 W,and magnetic field intensity of 0.8 T.The factors affecting the wear mass of Ni-TiN nanocomposite coatings can be obtained by the Range comparison:TiN nanoparticle addition amount>pulse power supply duty ratio>magnetic field strength>ultrasonic power>cathode current density.SEM analysis showed that there were some convex particles on the surface of the Ni-TiN nanocoating prepared by electrodeposition,and these particles would gradually decrease with the introduction of the ultrasonic field and magnetic field.When the multi-fields coupling deposition method was adopted,the convex structure of the composite coating would disappear basically,and the surface of the coating was relatively smooth and compact.AFM analysis indicated that the Ni-TiN nanocoating prepared by electrodeposition presented larger granular structure in the microcosmic region,the particle size of the composite coating was significantly smaller when the composite coating was prepared by ultrasonic electrodeposition and magnetic electrodeposition.And the particle size was further reduced and distributed evenly on the surface of the coating which was fabricated by multi field coupling deposition,and the surface quality of the coating was excellent.TEM analysis revealed that the TiN nanoparticles had little compound of TiN nanoparticles and more pores in the nanocomposite coatings prepared by electrodeposition,while the nanocomposite coating prepared by magnetic electrodeposition and ultrasonic electrodeposition had been improved well,the composite amount of TiN nanoparticles increased gradually.But there still existed the agglomeration of nanoparticles,the amount of TiN nanoparticles in the nanocomposite coating prepared by multi-fields coupling deposition method was more complex,and the size of the nanoparticles was about 30⁵0 nm.Besides,the coating had good tightness and almost had not defects.XRD analysis presented that it was observed that the diffraction peaks were at 44.82,52.21 and 76.77 degrees,corresponded to?1 1 1?,?2 0 0?and?2 2 0?crystal planes,respectively.The diffraction peaks were found at 36.66,42.60 and 61.81 degrees,corresponded to?1 1 1?,?2 0 0?and?2 2 0?,respectively,which proved that the coating contained Ni and TiN phases.According to the X ray diffraction data,the average grain sizes of Ni and TiN in the coatings were about 51.83 nm and 38.82 nm,respectively.Ni-TiN nanocoatings were deposited on the surfaces of cylinder liners,pistons and valve seats in F1-1600 type mud pumps by multi-fields coupling electrodeposition method.The surface microhardness of the repaired cylinder liner was increased from 634 Hv to 849 Hv,the corrosion rate of mud pump cylinder liner before and after restoration decreased from 20.4mg to 16.1 mg,and the wear mass decreased from 22.7 mg to 19.2 mg,when the test time was60 min.The surface of the repaired piston was smooth,and the corrosion pits and scratches before plating were not discerned by eye.The surface microhardness of the piston was increased from 622 Hv to 815 Hv,the amount corrosion of mud pump piston before and after restoration was reduced from 12.8 mg to 9.9 mg,and the wear mass decreased from 12.4 mg to 9.6 mg,when the test time was 60 min.After electroplating,the surface of the valve seat was smooth,and the surface microhardness was increased from 611 Hv to 826 Hv,the corrosion rate of mud pump valve seat before and after restoration decreased from 18.1 mg to15.5 mg,and the wear mass decreased from 15.6 mg to 11.3 mg,when the test time was 60min.The BP model was applied to predict the wear mass of the Ni-TiN nanocoating deposited on the surface of the key parts of the mud pumps.The results presented that the error between the predicted value and the experimental value was smaller,and the average error was 3.22%,the average error of prediction result is 7.17%by Neville polynomial interpolation.These findings indicated that the prediction accuracy of the BP neural network model was higher.It was also testified that the BP neural network model of multi-fields coupled deposited Ni-TiN nanocoatings on the surface of the key parts of mud pump had a high prediction accuracy and reliability,which could provide some technical supports for the performance prediction of other metal based nanocoatings.