| The in-situ growth of Al2O3 ceramic layer on the surface of aluminum alloy after micro arc oxidation treatment can improve its hardness and wear resistance.In the process of micro arc oxidation,in order to ensure the stability of the electrolyte and improve its conductivity,additives are often added to the main salt solution.The addition of additives in the electrolyte causes the composition phase of the micro arc oxidation ceramic layer to contain doped phases generated by electrolyte ions,and the type and content of the doped phases will affect the wear resistance of the ceramic layer.The paper selected three commonly used solution additives,NaVO3,Na2WO4,and K2ZrF6,to be added to phosphate based solutions.The effects of the type and content of electrolyte additives on the conductivity of the electrolyte and the growth characteristics of aluminum alloy micro arc oxidation ceramic layers were studied;The effect of additives on the passivation and film formation characteristics of aluminum alloy in electrolyte was studied through electrochemical voltammetry characteristics.The morphology,phase composition,and composition of the micro arc oxidation ceramic layer were analyzed using SEM,XRD,and EDS.The friction and wear characteristics of micro arc oxidation ceramic layers were studied through reciprocating friction and wear tests,and the wear failure mechanism of micro arc oxidation ceramic layers generated in different components of electrolytes was explored.Research shows:(1)NaVO3,Na2WO4,and K2ZrF6 solution additives within a certain concentration range,the growth rate of the thickness of the micro arc oxidation ceramic layer is mainly related to the type of additives,while the conductivity of the solution has little effect on the thickness of the film.Especially when the concentration of NaVO3 is above 0.0225 mol/L,the film thickness rapidly increases due to the large adsorption of vanadium on the surface of the film.(2)From the voltammetry curve,it can be seen that the addition of additives to the base solution has a significant impact on the interface characteristics of aluminum alloy solution.For NaVO3 and Na2WO4,changes in additive concentration have a relatively small impact on interface characteristics;And K2ZrF6 has a significant impact,when the concentration is greater than 0.0225 mol/L,within a certain potential range,its anodic oxidation current increases significantly with the increase of potential,and it has a strong destructive effect on the passivation layer of the aluminum alloy solution interface.(3)Compared to NaVO3 and K2ZrF6 solutions,adding Na2WO4 to the solution helps to formα-Al2O3 and WO3 phases have a significant effect on improving the hardness of the film layer.When the concentration of Na2WO4 is 0.015 mol/L,the film layer hardness can reach 1239.4 HV0.025.The vanadium oxide and zirconia in the film layer have a relatively small impact on the hardness of the film layer.Adding a small amount of NaVO3,Na2WO4,and K2ZrF6 additives to the solution resulted in a lower friction coefficient of the ceramic layer.(4)Adding 0.0150 mol/L Na2WO4 additive to the solution results in the latest wear failure of the film layer α-Al2O3 and WO3 have a significant impact on the wear resistance of the film layer.The main failure mode of the film layer is abrasive wear,where small abrasive particles grind and cut the surface of the ceramic layer,causing partial film layer fracture and detachment on the worn surface.When the concentration of NaVO3 solution additive is 0.0375 mol/L,the porosity and hardness of the film layer are lower,and the formation of large abrasive particles increases the degree of surface wear of the film layer.(5)The increase in friction load mainly reduces the time that the film layer exists in the stable friction and wear stage,and produces larger abrasive particles during the friction process,exacerbating the wear process of the film layer.At 10 N,there is a significant furrow phenomenon on the surface of the wear scar. |
PDF Full Text Request