Research On Wettability And Brazing Properties Of Nanosecond Laser Treated ZrO₂ Ceramic

Because of its low thermal expansion coefficient,high temperature resistance,good wear resistance,stable chemical properties,high resistivity,high refractive index and other advantages,ZrO₂ ceramics are often used as high temperature resistant materials,insulating materials,ceramic light shielding agent,so it is widely used in automotive,nuclear energy,aerospace,medical equipment and other fields.However,although ceramic materials have various excellent properties mentioned above,the high brittleness and poor toughness of the base material itself make ceramic materials often difficult to process,which seriously restricts the application of ceramic materials in various fields.Therefore,it is very necessary to realize the reliable connection between ceramics and ceramics or between ceramics and metals.There are great differences in physical and chemical properties between metals and ceramics,which makes it difficult for metals to wetting on the surface of ceramics.Therefore,nanosecond laser surface treatment was carried out on ZrO₂ ceramics in this project,aiming to improve the wettability of metals on the surface of ceramics.Then,the wettability of Sn-Ti/ZrO₂ ceramic system was studied.The interfacial structure and mechanical properties were analyzed.The surface of ZrO₂ ceramic treated by nanosecond laser was observed.The grid grooves were formed regularly on the surface of ZrO₂ ceramic,and the depth and height of the grooves were in the order of tens ofμorders of magnitude.The surface roughness of ZrO₂ ceramics is related to the laser processing parameters.Different grooves and roughness of ZrO2 ceramics were obtained by changing the laser scanning speed and laser power.The change of the surface wettability of ZrO₂ ceramics is the result of the joint action of the surface morphology and surface chemistry of ZrO₂ ceramics after laser processing.The changes of surface chemistry of ZrO2 ceramics are characterized by SEM,XRD and XPS.The wettability of Sn-xTi（x=1,3,5）alloy on the surface of ZrO₂ ceramics（untreated,1 h after nanosecond laser treatment and 7 days after nanosecond laser treatment）was investigated.The addition of active element Ti significantly promoted the wettability of Sn-xTi on the surface of ZrO₂.Sn-xTi（x=1,3,5）solders were used to connect ZrO₂ ceramics（untreated,1 h after nanosecond laser treatment,and 7 days after nanosecond laser treatment）.The interface characteristics of the joints were studied,the mechanical properties were tested,and the fracture characteristics were analyzed.The surface wettability of Sn-1Ti on ZrO₂ ceramics is poor and can not be spread out,so the discontinuous weld is formed.The shear strength of ZrO₂/ZrO₂ brazed joint increases with the increase of active element Ti content.Nanosecond laser treatment significantly improves the joint strength,and the maximum strength can reach39.15MPa.Nanosecond laser treatment of ZrO₂.It can be seen that the filler metal is embedded in the groove formed by nanosecond laser processing,and part of the fracture occurs on the filler metal and part of the fracture occurs on the brazing interface.The filler metal on the groove is stripped off,which also impedes the fracture to a certain extent.