Huaping Xiong

Wetting behavior of Co based active brazing alloys on SiC and the interfacial reactions

Abstract The wetting behavior of Co-based alloys on silicon carbide (SiC) was investigated by the sessile drop method. In vacuum at 1493 K for 10 min, the CoFeNi(Si, B)–(8–15)Cr–(14–21)Ti alloy exhibits good wettability on SiC, but after cooling fracture occurred within the SiC. The interfacial reactions were studied. The newly designed CoNi(Si, B)–Cr–Ti alloy is a promising brazing alloy for SiC.

Joining of Cf/SiC Composite With Pd-Co-V Brazing Filler

Carbon fibre-reinforced silicon carbide matrix composite (Cf/SiC composite) is a new heat-resistant ceramic matrix composite, and it shows a high potential for applications in high temperature environments. However, reliable joining technology is still lacking for this material. In the present paper, the contact angles of Pd-Co-V system alloys on Cf/SiC composite were measured using the sessile drop method. On this basis, one kind of Pd-Co-V alloy, in the powder form of the mixture of elemental components was used as brazing filler metal, and Cf/SiC composite joints were achieved after brazing at 1 523 K for 20 min. The microstructure of the Cf/SiC composite joints was examined with SEM and XEDS. It was found that elements Pd and V in the filler metal participated in the interfacial reactions between the composite and the brazing filler metal. The reaction products were analysed, and the joining mechanism was discussed.

Wettability and interfacial reactions of PdNi-based brazing fillers on C-C composite

Abstract The wettability and interfacial reactions of four kinds of PdNi-based brazing fillers on C-C composite were studied with the sessile drop method. The results showed that the wettability of these brazing fillers was improved with the increase of Cr content. Cr distributed at the interface of brazing filler/C-C composite and the formation of Cr 23 C 6 phase was speculated. In the interface between Ni-33Cr-24Pd-4Si brazing filler and C-C composite, element Cr reacted with C-C to form Cr-C reaction layer. Pd together with Si participated in the interfacial reactions and formed Pd 2 Si and Pd 3 Si phases. Furthermore, in this reaction zone, the residual brazing alloy became Ni-rich and Pd-depleted.

Liquid-phase siliconizing and aluminizing at the surface of a Ti3Al-based alloy and improvement in oxidation resistance

A simple and inexpensive method to modify the surface of a Ti 3 Al-based alloy, liquid-phase siliconizing and aluminizing by an Al-Si alloy, has been proposed. The surface modification at 1013 K for 10 min using Al-10 wt% Si melt resulted in a modified layer with a thickness of about 21 μm, composed of TiAl 3 and TiSi 2 . The coating improved the isothermal oxidation resistance of the Ti 3 Al-based alloy at 1073 K. A continuous alumina-rich scale was formed at the outermost surface after oxidation. SiO 2 was detectable in the oxide scale. The results of x-ray diffraction and x-ray energy dispersive spectrometer analysis showed that during oxidation, some of the TiSi 2 in the coating was oxidized to SiO 2 . In the meantime, the TiSi 2 was reduced to a lower silicide, Ti 5 Si 4 . The change of the surface microstructure after oxidation and the diffusion reaction between the coating and the Ti 3 Al substrate were also discussed.

Experimental investigation of phase equilibria in the Co–Ni–Zr ternary system

Abstract The phase equilibria of the Co–Ni–Zr ternary system at 1 000 °C, 1 100 °C and 1 200 °C were experimentally investigated by means of back-scattered electron imaging, electron probe microanalysis and X-ray diffraction on the equilibrated ternary alloys. In this study, no ternary compound is found. The (αCo, Ni) phase region extends from the Ni-rich corner to the Co-rich corner with small solubility of Zr at three sections. At 1 000 °C and 1 100 °C, Ni5Zr, Co2Zr and Ni10Zr7 phases have large solid solution ranges, but Ni10Zr7 phase disappears at 1 200 °C. The Ni7Zr2, NiZr, Co11Zr2, Co23Zr6 and CoZr phases exhibit nearly linear compounds in the studied sections, and have large composition ranges. Additionally, some differences in phase relationship exist among the above three isothermal sections.