Abstract
An integrated experimental-theoretical approach to the metallurgical characterization of the interfaces in steel plates clad by hot rolling is proposed. Three different couplings of materials have been studied: ASTM A 515 Gr.60 low carbon steel clad with austenitic stainless steel AISI 304L; extra low carbon steel ASTM A283 clad with high Ni content Alloy 59; and, low carbon steel AISI 1010 clad with Cu-Ni Monel 400. Experimental investigations, which are addressed to analyse the microstructural changes near the interfaces and identify the present phases, have been carried out through scanning electron microscopy (SEM) observations, microanalytical measurements by energy dispersive spectroscopy (EDS), and Vickers microhardness tests. In all of the cases examined, the zones that are affected by detrimental microstructural changes results in being considerably less thick than the overall cladding layer. Simulations that are based on theoretical diffusion modelling have been integrated to the experimental characterization by introducing a cladding parameter that acts on the diffusion bonding efficiency, in order to evaluate the effects of process temperature and time variations on diffusion bonding efficiency and stability. In particular, this analytical investigation has shown how the shorter is the duration of the diffusion transient and the higher the temperature, the lower results the sensitivity of the diffusion processes to temperature fluctuations.
Highlights
Low carbon steel plates or tubes, clad with different types of alloys, represent an economic solution to the growing demand for quality materials
In the zone that was affected by carbide precipitation, chromium depletion near the grain boundaries results in the austenite sensitization to the intercrystalline corrosion, as highlighted by the micrograph in Figure 7 that was taken after having carried out the ASTM Test A262-Practice E
Assuming that the diffusivity does not change with concentration, it is possible to calculate the D·t parameter in Equation (1) that gives a good fit of the energy dispersive spectroscopy (EDS) experimental profiles, as shown in Figure 15 for Ni diffusion at the interface ASTM A515 Gr.60/AISI 304 L
Summary
Low carbon steel plates or tubes, clad with different types of alloys, represent an economic solution to the growing demand for quality materials They benefit from having the peculiar properties of both base and clad metal, achieving good results in terms of mechanical performance, corrosion resistance, and lower cost if compared to the use of a massive high alloyed metal. For this reason, clad steels have been utilized with great success for several decades in process vessels, heat exchangers, chemical tanks, besides a variety of storage facilities [1], representing a great potential for applications in structural engineering [2] and shipbuilding [3]. The bonding interface that was obtained by explosion welding is wavy [9], so that shear strength of the interface is high, but this process needs specific requirements, as a dedicate place for explosion, and it results in serious pollution
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