Study On Properties And Dynamics Theory Of Electroless Ni-P Plating On Stainless Steel

Stainless steel has many distinct properties in such many fields as architectureindustry and chemical containers, which make the steel play a key role in modern society.Unfortunately, the low hardness and the poor anti-wear property of stainless steel obstructits application. Therefore, it is very significant for exploring the application by differentsurface processing of stainless steel in order to improve its anti-corrosion&anti-wearproperties.In this paper,202was taken as research object, with electroless Ni-P technologyregard as the technique to improve the surface anti-corrosion&anti-wear properties. Bymeans of orthogonal experiment, the optional process parameters of the prepared thickfilms was determined as follows: NiSO4·6H2O,20g/L; NaH2PO2-H2O,22.7g/L;CH3COONa,10g/L; C2H5NO2,8g/L; C4H6O4,7g/L; C6H5Na3O7.2H2O,15g/L; PH value,4.6, and temperature,88oC. Moreover, the phases and morphologies analysis, based onSEM and XRD, reveal that, the Ni-P coating surface is the amorphous high-phosphorusone, with the average content of P above9%.The dynamic mechanism of electroless single coating for202was investigated bymeans of optional technique. With increasing content of NaH2PO2, CH3COONa, C2H5NO2,HOOCCH2CH2COOH, and PH value, the coating speed is gradually enhanced. While,with increasing concentration of C6H5Na3O7.2H2O, the speed is yet lowered. Thecorresponding dynamic equation is deduced as follows:lg1.05lg H PO220.83lg L0.29lg H0.81lg A0.806lg S10942lg S28.56。Based on the aforementioned single coating prepared by high-phosphorus optionaltechnique, the thick coating was prepared by surface active treatment for single coating andrehydration in plating successfully. By means of orthogonal experiment, the optional process parameters of the prepared thick films was determined. The analysis of SEM andXRD on thick coating shows, the thick coating prepared by rehydration displays smoothsurface, with more small and uniform crystal grains as well as thickness of coating,100.44μm. The concentration of P is determined as11.83%. Furthermore, the crystallizationtemperature of the coating is about360oC, respectively. From the ageing treatment on thethick coating, the hardness is firstly promoted, and then lowered, with increasing annealingtemperatures. At the optimal annealing temperature,500oC, the maximal values ofhardness and wear loss are obtained simultaneously, i.e. hardness,1086.42HV, wear loss,43×10-4g. Upon different annealing temperatures, the wear mechanism of coating isdifferent. At low temperature, adhesive wear is dominant, with a trace of abrasive wear.While at above500oC, the abrasive wear is dominant.Different from single coating, the thick one has better wearing property due to theexistence of multi-layer structure. That is, the later coating can serve as sealing the formerone, which indicates better anti-wear property. For thick coating, at400oC, the optionalanti-wear property is present, which can be explained by the fact, i.e., a great deal of Ni3Pphase is precipitated, with smaller grain size. Also, the diffusion of P leads to uniformdistribution of Ni and Ni3P phase, which can lower the percentage of P in nickel alloyphase, raise corrosion potential, and then improve the anti-wear property.The three dispersing techniques, i.e., ultrasonic, high shear, and ultrasonic&highshear ones, are employed to test the dispersing effect of SiC in Ni-P-SiC composite plating.The results reveal that the ultrasonic&high shear dispersing technique is the best. Theoptimal dispersing effect is achieved on these conditions: shearing time,25min; shearingspeed, ultrasonic time,45min; ultrasonic frequency,35kHz; ultrasonic power,1000W.Based on the parameters, the mean particle size of SiC in in Ni-P-SiC composite plating is1.61μm.Upon these conditions, electroless Ni-P technology to coat dispersing SiC surface isthe best. Also, the aging treatment was conducted on the Ni-P-SiC composite plating. Atabout400oC, the crystallization occurs. At above500oC, the composite plating is mainly composed of Ni and Ni3P. When the plating is heated at about400oC, the mechanicalproperties, i.e. i.e. hardness,1584HV, wear loss,38×10-4g, are optimal. From the theprocess of aging treatment, the annealing temperatures can alter the wear mode ofNi-P-SiC composite plating. That is, when the annealing temperature is below300oC, thewear mode is dominantly adhesive wear, together with a little of abrasive one. However,when the annealing temperature is above500oC, the abrasive one is dominant, with a littleof adhesive one. At400oC, the wear mode is the adhesive one.