Technology And Mechanism Of Brazing Silicon Nitride To Steel With Ti-Ni-Nb Filler

The effects, which the components had, on the processes of brazing silicon nitride to steel were studied in this paper. Finally, Si3N4 was successfully brazed to steel using 40Ti-23Ni-37 Nb filler with proper temperature and holding time. The phases, microstructure and brazing mechanism of the joint were further discussed next.Titanium and ferrum transferred to TiFe through the reaction Ti+Feâ†'TiFe at 1458 K. Good reaction layers were getten with all different Ti-Ni-Nb fillers.In wetting experiment, the wetting property was enhanced as the contant of tianium or niobium decreases. Moreover, the minimum wetting angle of the seven different fillers were all below 20° with the help of precursor film, which means the fillers all could wet Si3N4 well enough. However, the Si3N4 and steel were only brazed successfully with 40Ti-23Ni-37 Nb, and there were cracks in joints which were brazed with other fillser. 40Ti-23Ni-37 Nb consisted of β(Nb,Ti), NiTi, NiTi2.It could also be found that titanium and niobium mainly determine the brazing reactions, but nikel stunted the reactions. Si3N4 did not react with the filler half of which was nickel. On the other hand, brazing temperature also had effect on the reactions. The reaction layer brazed at 1473 K and 1498 K mainly consisted of(Ti,Nb)5Si3, and α-Fe and FeSi occurred in the reaction layer of the joints brazed above 1520 K with N2 exist.The stear strength of the joint held 30 min at 1503 K was 71.8MPa, which was maximum among joints brazed with different parameter.