Study On Chemical Deposition Process And Properties Of Ni-P-PTFE Composite Coating

Friction and wear are common in production and life.The wear and tear of mechanical parts often causes hazards such as low equipment productivity,poor product quality and accelerated equipment aging,and even safety accidents in severe cases.In order to prevent the wear of the parts,it is usually necessary to deposit various wear-resistant metals or alloy materials on the surface of the parts to improve the service life of the parts that are often in a worn state.Chemical deposition is widely used in machinery because of its compact structure,uniform thickness,and can be deposited on the surface of parts of any shape.Especially in the absence of an external current,by adding a suitable reducing agent,the metal ions contained in the solution are reduced to metal atoms according to the oxidation-reduction reaction,and deposited on the surface of the workpiece to form a dense coating.As a classic surface coating,Ni-P alloy coating is widely used in various fields of industry,because it has good corrosion resistance,wear resistance and oxidation resistance.In order to further expand the electroless nickel layer to the application field and improve its performance,various countries have actively carried out research on the composite chemical deposition technology of co-depositing the second phase particles or more phase particles in the chemically deposited Ni-P alloy layer.The doped particles can form a complementary or progressive relationship with the Ni-P alloy coating in performance,so that a functional composite coating with more excellent physical properties can be obtained.In this study,the composition of the basic plating solution and plating conditions of Ni-P electroless plating were optimized,and PTFE particles with good self-lubricating properties were introduced on this basis.By studying the influence of main factors on the wear resistance of the composite coating,a Ni-P-PTFE composite coating with better wear resistance and friction reduction effect was prepared.That is,under the condition that the basic plating solution and the basic process parameters are unchanged,the various properties of the chemical deposition layer are improved by changing the concentration of different components in the solution.The purpose of this research is to obtain a coating with higher hardness,good self-lubricity and good corrosion resistance.A high-temperature and high-phosphorus process formula has been proposed,and a high-quality high-phosphorus coating has been successfully prepared.After the heat treatment process,the layer shows more excellent performance.And found that while ensuring a relatively fast deposition rate,the electroless plating solution can also exhibit better chemical stability during the plating process,which can basically reach the level of industrial application.The main research contents and conclusions are as follows:(1)Optimization of Ni-P alloy coating process parameters and plating solution formulaThe formula of Ni-P plating solution was optimized by orthogonal test,and the coating was prepared and its performance was characterized.In the formula:Ni SO₄30g/L,Na H₂PO₂20g/L,C₃H₆O₃18ml/L,C₂H₃Na O₂5.2g/L,C₆H₅Na₃O₇3.2g/L,CH₄N₂S 2mg/L,p H 4.8,temperature On the basis of 85?,the influences of 4 factors including reducing agent sodium hypophosphite,stabilizer thiourea,p H value,and temperature on the average deposition rate and phosphorus content in the deposited layer were investigated,and a better formula and plating were obtained.Process:Ni SO₄28g/L,Na H₂PO₂25g/L,C₃H₆O₃18ml/L,C₂H₃Na O₂5.2g/L,CH₄N₂S 0.8mg/L,C₆H₅Na₃O₇3.2g/L,p H 4.8,temperature 85°C,plating The time is 1.5h;the coating obtained under this formula and process conditions is thicker and denser,and the deposition speed is faster.The average deposition rate is 0.6214g in 90 minutes,the phosphorus content is higher than 9%,and the hardness is also ideal(2)The effect of PTFE particle dispersion on the properties of the composite coating The effects of mechanical stirring,magnetic stirring and ultrasonic dispersion on the properties of Ni-P-PTFE composite coatings were discussed.Through comparative analysis,it is concluded that the quality of composite coating prepared by PTFE(60%)emulsion is better than that prepared by PTFE powder.In terms of dispersion effect of PTFE particles,ultrasonic dispersion effect is better than magnetic stirring,magnetic stirring is better than mechanical stirring.Because the ultrasonic dispersion was only carried out at the ultrasonic power of 20W,although the PTFE in the composite coating was uniformly dispersed and the particle size was small,the content of PTFE in the deposition layer was less.The results show that the best mechanical stirring speed is 200r/min,and the best magnetic stirring speed is 450r/min,the quality of the deposition layer is better,and the content of PTFE particles in the composite coating is higher.The effect of magnetic stirring speed on the content of PTFE,deposition rate,hardness and friction coefficient of composite coating was studied.The results show that when the magnetic stirring speed is450r/min,the composite coating has good quality and performance,and the deposition rate is fast,which can meet the requirements of industrial application.(3)Preparation of Ni-P-PTFE antifriction and wear-resisting composite coatingPTFE particles with self-lubricating properties were introduced on the basis of the optimized formulation of Ni-P bath,and dispersed by magnetic stirring at 450r/min with better effect.By comparing the properties of the composite coating obtained by adding different concentrations of PTFE emulsion,the friction coefficient is the smallest when the concentration is 8ml/L,and the phosphorus content is higher.Then the prepared composite coating was subjected to heat treatment at 300?(1h).The hardness of the composite coating was improved greatly,the friction coefficient was further reduced,and the binding force was increased by 33%.Although the corrosion resistance was slightly decreased,the composite coating showed good wear resistance and friction reduction.It plays an important role in the further industrial application of Ni-P-PTFE composite coating.