Interaction of composite ceramics based on zirconium diboride with high temperature alloys based on iron and nickel

The solid-phase interaction and contact melting of the ZrB2-15 vol. % MoSi2 with Fe alloy, and Ni base-alloys were carried out. It has been established that in the composite-Fe alloy system up to a temperature of 1200 degrees C in vacuum, there is no chemical interaction with the formation of new phases at the contact boundary. Changes occur only in the near-contact zone of the composite: MoSi2 disappears with the formation of pores in its place, and from the side of the metal there is a zone enriched with silicon. Similar processes are observed during solid-phase interaction in the systems ZrB2-15 vol. % MoSi2-Ni base alloys. However, in these systems, in addition to the diffusion of silicon from the composite into the alloy, counter diffusion of chromium from the metal to the contact boundary and into the composite occurs, followed by interaction and the formation of a layer of a new Cr2B phase. At temperatures above 1200 degrees C, contact melting occurs and a multilayer structure is formed over the cross section of contacting pairs. In this case, for the system with steel, the main phases are the base of stainless steel saturated with silicon and zirconium and the phases: (Fe,Cr)(2)B, (Ni,Fe)(16)Si7Zr6, (Mo,Cr,W)B-2 and ZrB2. In the nichrome alloy system, the main phases are silicon alloyed nickel, Ni3Si, Ni16Si7Zr6 silicides and (Cr,Mo)(2)B, (Mo,Cr,W)B-2 and ZrB2 borides. These studies demonstrate that in contact pairs ZrB2-15 vol. % MoSi2 - an alloy based on iron and nickel, the maximum operating temperature is 1000 degrees C. In the case of more severe operating modes with temperatures of 1200 degrees C and above, it is necessary to create barrier layers at the contact boundary to prevent possible diffusion and contact melting of the contacting pairs.