Effects Of The Composite Electrolyte For Micro-arc Oxidation On The Bonding Strength Between Titanium And Porcelain

Objective: To investigate the effects of the composite electrolyte for micro-arc oxidation(MAO)on the bonding strength between titanium and porcelain.Methods: The composite electrolyte of Na2 Si O3 and Mg Si F6 was chosen as MAO reaction solutions.There were nine groups: 20g/L Mg Si F6(group A)、20g/L Mg Si F6+1g/L Na2 Si O3(group B)、20g/L Mg Si F6+2g/L Na2 Si O3(group C)、20g/L Mg Si F6+3g/L Na2 Si O3(group D)、20g/L Mg Si F6+4g/L Na2 Si O3(group E)、20g/L Mg Si F6+5g/L Na2 Si O3(group F)、20g/L Mg Si F6+10g/L Na2 Si O3(group G)、20g/L Mg Si F6+20g/L Na2 Si O3(group H)and the sandblasting treatment was selected as a control group(group I).Two samples in each group were selected to analyze the coating formed by scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).According to ISO 9693,after different treatments disposed and porcelain fused on the remaining titanium specimens,six titanium porcelain specimens were selected in each group and the bonding strengths of the titanium-porcelain were measured by the three-point bending test.The surface of the samples after three-point bending test were observed using SEM as well.The last two titanium porcelain specimens of each group were embedded with epoxy resin.Then the bonding interface between titanium and porcelain was exposed and analyzed by scanning electron microscope(SEM).Results: The mean bond strength of the eight micro-arc oxidation groups,and the control group were 38.93±2.14 MPa(group A)、36.90±2.25 MPa(group B)、43.01±1.30 MPa(group C)和 32.55±3.07 MPa(group D),31.14±3.22 MPa(group E),23.46±2.54 MPa(group F),26.36±3.57 MPa(group G),28.91±4.51 MPa(group H),27.86±1.70 MPa(group I)respectively.The bond strengths of group A、group B and group C were significantly higher than the control group(p<0.05).There was no significant difference in the bonding strength between the experimental group e,g and h and the control group I(p > 0.05).The bond strengths of group F were lower than the control group(p<0.05).When the titanium were treated by micro-arc oxidation with 20g/L Mg Si F6 and 2g/L Na2 Si O3,it had higher bonding strength than that in any other groups(P<0.05).The surfaces of the samples in micro-arc oxidation group A、 group B、group C and group D were porous and homogeneous while the sample in the control group was sharp and rough.The number of micropores in group C was more than that in other groups,and the diameter of micropores in group C was about 1μm.The membrane structure of samples in both group D and group E were defective.The membrane micropores of Group F were mutually fused.As for group G,largediameter protrusion were found in that film layer,and the film lay was uneven.In group H,although the membrane was porous,the pore size was not uniform,and some areas were honeycomb.After three-point bending test,the residual porcelains of group C were more than that of other groups.A small amount of porcelains remained on the group I while group F had almost no porcelains residue.There were no obvious cracks and defects in the titanium-ceramic bonding interface of group A and group C while there were holes and cracks in the cross sections of titanium ceramic specimens of the other experimental groups.In sandblasting group,the crack between pure titanium substrate and porcelain was obvious,and thick oxide film was observed.Conclusions: Micro-arc oxidation electrolyte plays an important role in the microstructure and physical and chemical properties of ceramic membrane.The micro-arc oxidation treatment by suitable proportion of composite electrolyte could be an effective method for increasing the titanium-porcelain bonding strength.