Producibility of brazed high-dimension centrifugal compressor impellers

The centrifugal compressor impeller is a high technology machine part and its manufacture is a demanding process. The paper shows that it is possible to join high-dimensional impellers parts by brazing. Various aspects of the construction and the brazing process of high-dimensional impellers have been considered and some modifications of the brazing have been proposed. The method was applied in industry with a good result. Vacuum brazing tests were carried out on age-hardened steel of the 14-5 pH type using 82Au-18Ni solder. It was found that the joint has a multi-layer structure consisting of two kinds of Au-Ni solid solutions: one is rich in gold and the other is rich in nickel. The influence of the roughness of the surfaces to be joined and the distance between them on the joint structure and properties have been determined. The maximum tensile strength (R-m = 1265 MN/m(2)) was obtained for joints of polished surfaces without any distance elements, brazed at a temperature of 1273 K for 7.2 ks (2 h) and aged at a temperature of 723 K for 7.2 ks (2 h). (C) 2002 Elsevier Science B.V. All rights reserved.