Analysis of the Structure, Phase Composition and Mechanical Properties of a Tubular Welded Joint from Refractory Alloy HP40NbTi

The methods of optical and electron microscopy and x-ray spectrum microanalysis are used to study the microstructure and phase composition of a tubular welded joint from alloy HP40NbTi based on the Fe – 25Cr – 35Ni system. Short-term and long-term mechanical properties of the alloy are determined. The joint is characterized by structural inhomogeneity and formation of silicon segregations and G-phase in the structure of the metal in the heat-affected zone. It is shown that the special features of the structure of the welded joint from alloy HP40NbTi lower considerably its mechanical properties at the operating temperatures of pyrolysis facilities.