Effect of friction welding parameters on the tensile strength and microstructural properties of dissimilar AISI 1020-ASTM A536 joints

Radosław Winiczenko

doi:10.1007/s00170-015-7751-5

Abstract

This paper presents an effect of friction welding parameters on the tensile strength and microstructural properties of dissimilar AISI 1020-ASTM A536 joints. A hybrid response surface methodology (RSM) and genetic algorithm (GA)-based technique were successfully developed to model, simulate, and optimise the welding parameters. Direct and interaction effects of process parameters on the ultimate tensile strength (UTS) were studied by plotting graphs. Friction force and friction time have a positive effect on tensile strength. As friction force and friction time increase, the tensile strength also increases. The maximum tensile strength of the friction-welded low carbon steel-ductile iron joints was 87 % of that of the base metal. The tensile properties, microstructure, Vickers hardness distribution, and fracture morphology of the welded specimen have been studied and presented in this study. Additionally, the distribution of carbon element on both sides of the interface was estimated using energy-dispersive spectroscopy (EDS). The results of the metallographic study show clearly that the friction welding process was accompanied by a diffusion of carbon atoms from ductile iron to steel. This process causes the formation of a carbon-rich zone at the interface and decarburization zone in the ductile iron close to the bond interface.

Highlights

Ductile iron castings are used for many structural applications, those requiring strength and toughness combined with good machinability and low cost
The relationship between ultimate tensile strength (UTS) of the friction-welded low carbon steel (LCS)-ductile iron (DI) joint is a function of the friction welding parameters such as a friction force (F), Table 2 Mechanical properties of the base materials
The results clearly showed that the friction welding process is inherent to the process of carbon transport through the DI-LCS steel interface

Summary

Introduction

Ductile iron castings are used for many structural applications, those requiring strength and toughness combined with good machinability and low cost. Special materials and techniques are available for the repair welding of ductile iron castings or for joining ductile iron to itself or to other ferrous materials, such as mild steel, austenitic steel, and grey, nodular or malleable iron [3]. Ductile irons contain higher amounts of carbon compared to steels which diffuse into the austenite during welding, forming hard brittle phases at the weld interface, namely martensite and carbides. These give rise to poor elongation properties and high hardness values, as reported by Pascual et al [5]. The main objective is to avoid the formation of cementite in the matrix material, which makes the welded region brittle, but in ductile iron, an additional objective is of almost equal importance, concerning the retention of a nodular form of graphite [7]

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Conclusion