The Cr-Ni-Zr (Chromium-Nickel-Zirconium) System

Abstract

The Cr-Ni-Zr system was reviewed by [2000Gup]. In developing high temperature resistant brazing material, the Cr-Ni-Zr system has been studied at the Ni-corner. The results are given here. In order to discuss the new results on Cr-Ni-Zr system, it is necessary to recapitulate the binary systems. The Cr-Ni system [1991Nas] (Fig. 1) is a simple eutectic system, the eutectic reaction L M a + c occurring at 1345 C, where a and c are the terminal solid solutions of body centered (bcc) Cr and face centered cubic (fcc) Ni, respectively. At the eutectic reaction temperature, the c phase extends to 50 at.% Cr and the a phase extends to 32 at.% Ni. Solubility of Ni in Cr decreases with decrease in temperature reasonably fast down to 1100 C. A Ni2Cr ordered phase forms in the c phase region below 600 C. The Cr-Zr system [Massalski2, 1993Oka] shows (Fig. 2) the presence of only one intermediate phase Cr2Zr which occurs in three polymorphic forms, the aCr2Zr(w1) exists below 1592 C, the bCr2Zr(b1) exists between 1592 and 1622 C, and the cCr2Zr(c1) exists between 1622 and 1673 C. Two eutectics, L M a + b1 and L M w1 + a¢ occur at 1592 and 1332 C, respectively. The a¢ phase is the terminal solid solution of bZr. A eutectoid reaction a¢ M x + w1 occurs at 831 C with x representing the aZr phase. The solubility of Zr in Cr is negligible at room temperature and is 1.5 at.% Zr at the eutectic temperature 1592 C. The Ni-Zr system [1991Nas] (Fig. 3) has eight intermediate phases Ni5Zr(e), Ni7Zr2(p), Ni3Zr(k), Ni21Zr8(h), Ni10Zr7(b), Ni11Zr9(m), NiZr(/), and NiZr2(n). The p, /, and n phases melt congruently at 1440, 1260, and 1120 C, respectively. All the other intermediate phases form through peritectic or peritectoid reactions: L + p M e, L + p M h, p + h M k, L + / M m1, and L + m M b occurring at 1300, 1180, 920, 1170, and 1160 C, respectively. Five eutectic or eutectoid reactions: L M c + e, L M h + b, L M / + n, L M n + a¢, and a¢ M n + x occur at 1170, 1070, 1010, 960, and 845 C, respectively. The m phase undergoes eutectoid transformation m M b + / at 978 C. The phases and their structure data are given in the review paper [2000Gup]. [1999Kho] reinvestigated the Cr-Ni-Zr system at the Ni-rich corner, up to 40 at.% Cr and up to 30 at.% Zr. The alloys were melted in a water cooled copper hearth, tungsten electrode arc furnace under argon atmosphere. The component elements were Ni of 99.95 mass% purity, Cr of 99.98 mass% purity, and Zr of 99.95 mass% purity. The alloys in cast condition were used for this investigation.