Effect of Ti[sbnd]Cr filler on microstructure, mechanical properties, and thermal shock resistance of TZM/graphite brazed joints

Abstract

The objective of this work was to braze titanium zirconium molybdenum(TZM) alloy and graphite with Ti40Cr filler in order to explore its practical application on computed tomography tube target. The brazed joints' microstructure, mechanical properties, and thermal shock properties were characterized by X-ray diffraction, scanning electron microscopy, and a 3D laser confocal measuring microscope. The results indicated that the interface microstructure of TZM/graphite brazed joints was graphite/Cr3C2/TiC/Ti-Cr(Mo)/Ti-Mo(Cr)/TZM, and the thickness of the brazing seam increases with increasing temperature. In contrast, the thickness of the carbide reaction layer near the graphite side gradually becomes thicker. The shear tests showed that the joint's strength increased with the temperature increase in a specific temperature range. Maximum shear strength of 26.5 MPa was reached when the joint with groove structure brazed at 1480 °C. The effect of holding time on the joints was similar to that of temperature, but the thickness of the carbide reaction layer did not change with holding time. The optimal brazing process for TZM/Ti-40Cr/graphite brazed joints was to hold for 20 min at 1480 °C. TZM/Ti-40Cr/graphite brazed joints were subjected to a laser thermal shock test. The results indicated that TZM/Ti-40Cr/ graphite brazed joints would not cause serious damage when subjected to 20A laser beam current. When the current rose to 40A, the joints will be broken down by the laser, and the damage depth reached −254.824 μm.