Analysis of bimetal pipe bends with a bend of 0.7D with a cladding layer of Inconel 625

Abstract

Bimetal pipes are highly stressed composite components that must resist corrosion in a chemically aggressive environment. The production of pipe bends with a supercritical bend of 0.7D, which form the part of serpentine systems, is very complex and technologically demanding, because very often undesired cracks occur. To increase the service life of these serpentine systems, the use of a 16Mo3 base steel pipe with a cladding layer of Inconel 625 material was proposed for their production in order to signi cantly increase their corrosion resistance. For this reason, an extensive analysis of the production of pipe bends with a supercritical bend of 0.7D from bimetal pipes with Inconel 625 cladding was performed, which addressed not only the bend but also the mechanical properties of the pipe with Inconel 625 cladding. It was found out that the production of the pipe bend with a bend of 0.7D of a bimetal pipe is feasible completely without defects with perfectly satisfactory mechanical properties.

Processing of Bimetallic Inconel 625-16Mo3 Steel Tube via Supercritical Bend: Study of the Mechanical Properties and Structure

“…The material changes in the layer hardness are related to detected changes in the shape and morphology of γ dendrites. The results of the presented investigation also correspond to the authors' previous study of the strength properties in various areas within the whole substrate layer system, including the heat-affected zone [13].…”

“…The coated tube is bent by supercritical bending (d ≤ 0.7D; d is the diameter of the bend; D is the diameter of the tube) as part of the manufacturing process of the incinerator component [13,14]. The parameters and mechanical properties of the bend were analyzed, and a specific procedure was developed to cold-bend the tube with the use of sand filling inside to bend it without cracking and excessive deformation of its cross-section [13,14].…”

“…Previous works by the authors' collective [13,14] were focused on the study of the ability to create critical and supercritical bends in bimetal pipes (i.e., bends smaller than 1D, specifically 0.7D) with Inconel 625 cladding, and this solution has not been published in any other study so far. While these previous studies mainly dealt with the technological parameters of the bending process in relation to the presence of possible defects, this work is focused on the detailed material investigation of the microstructure and nanomechanical properties (nanohardness, reduced modulus) of an Inconel 625 cladding layer in different areas affected by stresses caused by the bending process.…”