Usage of microscopic methods in analysis of non-conforming nickel alloy products

Abstract

The process of creating products with the required utility properties is a multi-stage process determined by a number of factors that determine the resulting quality. Today, given the pressure on the economic side of production, companies have limited input control to the minimum possible. Spectral analysis, material hardness evaluation, or layer thickness control are most often performed. They carry out other analyses in companies sporadically. Common input analyses often do not reveal the actual state of the microstructure such as the presence of undesirable phases, their size, phase distribution, their heterogeneity, etc. These factors affect the weldability and cold formability of the workpiece, and consequently affect the resulting product quality and product life. In the case of bellows production, the input semi-finished products are subject to requirements in terms of technological division of production, which includes input cutting, welding, forming and calibration of the finished product. Even in nickel alloys, the more chemically and structurally complicated the material, the lower its formability. An important factor influencing the formability of these alloys is the occurrence of inclusions. The negative influence of inclusions on cold formability depends on the chemical composition, mechanical properties, their morphology, frequency and distribution in the base matrix. In terms of weldability, nickel alloys are very well weldable. Their weldability is dependent on chemical purity, especially sulphur, carbon and chromium content. The influence of other alloying elements on the weldability of nickel alloys is minimal. Only precipitation-hardened alloys are more difficult to weld. Almost all welding methods as with steel can be used. The paper presents the use of microscopic methods for detecting the causes of non-conforming bellows from nickel alloys.