High-temperature brazing of high-temperature castingalloys by boron containing braze alloy doped with silicon

Abstract

The essence of the work consists in development of the process of neutralizing the negative influence of boron in the composite braze alloy of Ni-Co-Cr-Al-2,5%(mas.) B + filler-alloy Rene-142 by adding to it (15-25)% (wt.) of Ni-12%Si braze alloy of an eutectic composition. Precipitation of dispersed carbo-boride phases uniformly distributed in the solder, the volume fraction of which after heat treatment is equal to ƒ = 4,7- 5,9%, and the almost globular shape of carbide particles allowed improvement of technological ductility and strength of high-temperature brazed joints. Addition of Ni-12% Si braze alloy powder to boron-containing Ni-Co-Cr-Al-2,5B-Rene-142 composite alloy prevents formation of γ-Ni + CrB boride eutectics, the formation of which leads to lowering of high-temperature resistance of brazed metal and brittle fracture of joints below the yield point. Braze alloy doping with silicon results in lowering of the level of inner stresses of the matrix solution crystalline lattice, Systematic analysis of the microstructure, phase composition, strength and ductility of brazed metal in joints of ChS70VI, VZhL12U, ZhS26VI and DS alloys. Depending on the type of brazed alloys, BJ Q-factor ( σ_s^BJ/σ_s^BM) at 20 ^оC was 0,9 to 1.