A Study Of Cu-Ni-Ti Amorphous High-temperature Filler Alloy Brazing Si₃N₄Ceramics

Si3N4ceramics is an excellect high-temperature material, it is importantal practice significance to effectively bond filler alloy and Si3N4ceramics.In this paper,we successfully made CuNi12Ti35amorphous filler alloy by single-roll rapidly cooled equipment and studied the structure、composition distribution melting characteristics of filler alloy with DSC、SEM、EDS and XRD.The effect of brazing temperature、hold time and Ti wt%on wettability and bonding strength for the joints was investigated.The comparison analysis was carried out between amorphous and crystalline filler alloy, and studied the effect of fourth elements on joint strength.The interfacial reaction thickness and morphology of reaction layer at the joints was annlysed by means of SEM and EDS.The brazing mechanism of the joints was discussed. Conclusions are as follows:(1) DSC and XRD confirm foil belt filler is amorphous.If brazing temperature、holding time or Ti wt%increased, spreading area of CuNi12Ti35crystalline/amorphous filler alloy on Si3N4ceramics became much bigger.When we use CuNi12Ti35filler alloy brazing Si3N4ceramics,active element Ti diffuse to the interface between Si3N4ceramics and filler mater, then Ti react with Si3N4ceramics and form two interfacial reaction layer.The reaction layer I which close to Si3N4ceramics is composed of TiN.The reaction layer II is composed of Ti5Si3.(2) If we enhance holding time,it will increase the thinkness of reaction layer Ⅰ and Ⅱ.When holding time to be enhanced, the thinkness of reaction layer I almost did not change,but the thinkness of reaction layer Ⅱ increased obviously.As we all know, the thinkness and morphology reaction layer have an important influence on the bonding strength.The joints exhibited a highest room temperature strength of314.7MPa which was brazed with CuNi12Ti35amorphous filler alloy at1100℃for10min.The joint strength is123.5MPa when test temperature is500℃.Under the same experimental condition, the bonding strength and wettability on Si3N4ceramics of amorphous filler alloy are all stronger than the crystalline one with the same composition.With Ce or Y content in filler alloy increaing in a certain range will improve bonding strength, but add Si content in filler alloy will reduce bonding strength.(3) Because amorphous filler alloy will emit a lot of heat before it melt.This will help Ti atom diffuse into the touch interface between Si3N4ceramics and filler alloy.It will reduce the time of phsial wettability and increase the time of reactive wettability.Compared with amorphous filler alloy, reactive wettability of crystalline ones is behand.The composition distribution of amorphous filler alloy is uniform,so it instantly and evenly melting、wetting、clearance filling.It is good for enhancing the intensive of interfacial reaction layers and improving same defect as void and crack.It is also beneficial to get reliable joints.