A novel arc heat treatment technique for producing graded microstructures through controlled temperature gradients

Hosseini, Vahid A.; Karlsson, Leif; Hurtig, Kjell; Choquet, Isabelle; Engelberg, Dirk; Roy, Matthew; Kumara, Chamara

doi:10.1016/j.matdes.2017.02.042

Cited by 22 publications

(17 citation statements)

References 19 publications

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“…2.2. Figure3 shows that the thermal properties of the 2507 type base material and the 2509 type filler material are nearly identical why the existing model [17] could be applied to the weld metal samples. Equilibrium phase fractions and TTP diagrams were calculated using JMatPro, version 6.2.1, for the actual chemical composition of the filler material (Table 1).…”

Section: Temperature Field Modeling and Thermodynamic Calculationsmentioning

confidence: 80%

“…However, these methods are timeconsuming when used to cover a large range of times and temperatures. Hosseini et al [17] recently introduced a novel heat treatment technique where a stationary TIG arc is applied on a disk-shape specimen. This method makes it possible to cover the full range of temperatures from room temperature to liquidus in a single specimen, thereby greatly reducing the number of samples needed and also the characterization time required.…”

Section: Recommended For Publication By Commission IX -Behaviour Of Mmentioning

confidence: 99%

“…An arc current of 100 A and an arc length of 3 mm were used to heat treat two samples for 1 and 10 min, respectively. More details about the arc heat treatment technique can be found in [17].…”

Section: Arc Heat Treatmentmentioning

confidence: 99%

“…The steady-state temperature distribution around the fusion zone has previously been modeled using the open source computational software OpenFOAM® [17,20]. The existing model was used but adapted to the actual geometries of the fusion zones in the 1-and 10-min arc heat-treated samples.…”

Section: Temperature Field Modeling and Thermodynamic Calculationsmentioning

confidence: 99%

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Time-temperature-precipitation and property diagrams for super duplex stainless steel weld metals

et al. 2018

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Super duplex stainless steel (SDSS) weld metal microstructures, covering the complete temperature range from ambient to liquidus, were produced by arc heat treatment for 1 and 10 min. Temperature modeling and thermodynamic calculations complemented microstructural studies, hardness mapping and sensitization testing. After 1 min, intermetallics such as sigma and chi phase had precipitated, resulting in moderate sensitization at 720-840°C. After 10 min, larger amounts of intermetallics resulted in hardness up to 400 HV0.5 and more severe sensitization at 580-920°C. Coarse and fine secondary austenite precipitated at high and low temperatures, respectively: The finer secondary austenite was more detrimental to corrosion resistance due to its lower content of Cr, Mo, and N as predicted by thermodynamic calculations. Increased hardness and etching response suggest that 475°C embrittlement had occurred after 10 min. Results are summarized as time-temperature-precipitation and property diagrams for hardness and sensitization.

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Section: Temperature Field Modeling and Thermodynamic Calculationsmentioning

confidence: 80%

Section: Recommended For Publication By Commission IX -Behaviour Of Mmentioning

confidence: 99%

Section: Arc Heat Treatmentmentioning

confidence: 99%

Section: Temperature Field Modeling and Thermodynamic Calculationsmentioning

confidence: 99%

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Time-temperature-precipitation and property diagrams for super duplex stainless steel weld metals

et al. 2018

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“…Hosseini et al [13] introduced a novel heat treatment technique to fabricate FGMs that are suitable to study the microstructures forming over a wide range of temperatures. With this method, a stationary tungsten inert gas (TIG) arc creates a steady-state temperature gradient for chosen times ranging from a few seconds to several hours.…”

Section: Introductionmentioning

confidence: 99%

Effect of Sigma Phase Morphology on the Degradation of Properties in a Super Duplex Stainless Steel

et al. 2018

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Sigma phase is commonly considered to be the most deleterious secondary phase precipitating in duplex stainless steels, as it results in an extreme reduction of corrosion resistance and toughness. Previous studies have mainly focused on the kinetics of sigma phase precipitation and influences on properties and only a few works have studied the morphology of sigma phase and its influences on material properties. Therefore, the influence of sigma phase morphology on the degradation of corrosion resistance and mechanical properties of 2507 super duplex stainless steel (SDSS) was studied after 10 h of arc heat treatment using optical and scanning electron microscopy, electron backscattered diffraction analysis, corrosion testing, and thermodynamic calculations. A stationary arc was applied on the 2507 SDSS disc mounted on a water-cooled chamber, producing a steady-state temperature gradient covering the entire temperature range from room temperature to the melting point. Sigma phase was the major intermetallic precipitating between 630 °C and 1010 °C and its morphology changed from blocky to fine coral-shaped with decreasing aging temperature. At the same time, the average thickness of the precipitates decreased from 2.9 µm to 0.5 µm. The chemical composition of sigma was similar to that predicted by thermodynamic calculations when formed at 800–900 °C, but deviated at higher and lower temperatures. The formation of blocky sigma phase introduced local strain in the bulk of the primary austenite grains. However, the local strain was most pronounced in the secondary austenite grains next to the coral-shaped sigma phase precipitating at lower temperatures. Microstructures with blocky and coral-shaped sigma phase particles were prone to develop microscale cracks and local corrosion, respectively. Local corrosion occurred primarily in ferrite and in secondary austenite, which was predicted by thermodynamic calculations to have a low pitting resistance equivalent. To conclude, the influence of sigma phase morphology on the degradation of properties was summarized in two diagrams as functions of the level of static load and the severity of the corrosive environment.

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Nanoscale phase separations in as-fabricated thick super duplex stainless steels

et al. 2021

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Nanoscale phase separations, and effects of these, were studied for thick super duplex stainless steel products by atom probe tomography and mechanical testing. Although nanoscale phase separations typically occur during long-time service at intermediate temperatures (300–500° C, our results show that slowly cooled products start to develop Fe and Cr separation and/or precipitation of Cu-rich particles already during fabrication. Copper significantly slowed down the kinetics at the expense of Cu-rich particle precipitation, where the high-copper material subjected to hot isostatic pressing (HIP), with Δt500–400 of 160 s and the low-copper hot-rolled plate with Δt500–400 of 2 s had the same level of Fe and Cr separation. The phase separations resulted in lower toughness and higher hardness of the HIP material than for hot-rolled plate. Therefore, both local cooling rate dependent and alloy composition governed variations of phase separations can be expected in as-fabricated condition.

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A novel arc heat treatment technique for producing graded microstructures through controlled temperature gradients

Cited by 22 publications

References 19 publications

Time-temperature-precipitation and property diagrams for super duplex stainless steel weld metals

Time-temperature-precipitation and property diagrams for super duplex stainless steel weld metals

Effect of Sigma Phase Morphology on the Degradation of Properties in a Super Duplex Stainless Steel

Nanoscale phase separations in as-fabricated thick super duplex stainless steels

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