Pipe-to-pipe friction welding of dissimilar Al-SS joints for cryogenic applications

Abstract

In the present investigation, dissimilar materials such as AA6063 and SS304L having pipe dimensions of 60.33 mm outer diameter and 3.9 mm wall thickness were friction-welded with different conditions of process parameters. Nondestructive tests such as radiography test (RT) and liquid penetration test (LPT) were carried out on the welded pipes in order to qualify weld joint. Thermal shock test and helium leak tests were performed on the successful welded samples in order to check its ability to work with cryogenic application. The results revealed that the pipe-to-pipe configuration of dissimilar Al-SS joints was produced successfully by friction welding using continuous drive. There were no defects presented in the joint area as revealed by RT and LPT. Thermal shock test and helium leak tests have also confirmed the soundness of joints. Higher deformation of Al base material results in the huge flash formation of Al that results in the sleeve formation of Al pipe on SS pipe. The helium leak test has confirmed the soundness of joints without any defects after its testing at 1.2 psi pressure. More than 60% of joint efficiency was obtained from Al-SS friction-welded joints.

Processing and evaluation of dissimilar Al-SS friction welding of pipe configuration: Nondestructive inspection, properties, and microstructure

“…The flash formation from the Al side was observed in all the conditions, whereas no macroscopic deformation of SS was observed. This is quite obvious and in line with the large softening behavior of Al compared to SS, which was also noticed in the previous literature of [10,22,36,37]. However, differences in flash formation have suggested parametric variations of experiments with different conditions.…”

“…The maximum obtained UTS of 194.79 MPa was 72% of the AA6063-T6 material, which can be considered as an acceptable range of dissimilar pipe welded joints of AA6063-T6 and SS304L combination. So far, in pipe friction welding of Al-SS combination, the obtained joint efficiency of 72% in the present investigation was highest as compared to published literature of [10,27,34]. The presence of IMCs at the interface may be the reason for less joint efficiency as they were known for the deterioration of mechanical properties.…”

“…These constant parameters were selected based on the previous study of Vyas et al [10]. The variations in friction time, friction force, upset pressure, and burn off length are shown in Table 3, which were varied based on visual inspection of flash one by another.…”

“…However, they used a 14 mm diameter of pipe with inappropriate testing methods without removing flash from the welds. In another study of Al-SS pipe friction welding by Vyas et al [10], the diameter of the pipe was around 60 mm, wherein the obtained joint efficiency was 60 %. The improvement in the joint efficiency and friction welding for higher diameter applications is still an active area of research.…”

“…The solidstate joining is helpful to build high quality joint for dissimilar materials due to capabilities to handle metallurgical complexities [8][9]. Dissimilar materials combination of aluminum (Al) and stainless steel (SS) is one of those interesting bimetal joints applied in various industries with a variety of applications such as cryogenic heat exchangers' transition joint, automotive structural joints, vacuum applications, rocket's propulsion systems and many more [10]. Cost and weight reduction benefits can be greatly obtained with density differences of Al and SS along with an advantage of hybrid properties of components [11][12].…”