Hydrogen diffusion in creep-resistant 9% Cr P91 multi-layer weld metal

Rhode, Michael; Richter, Tim; Mayr, P.; Nitsche, Alexander; Mente, Tobias; Böllinghaus, Thomas

doi:10.1007/s40194-019-00828-8

Cited by 8 publications

(12 citation statements)

References 44 publications

(87 reference statements)

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“…SA with increased wire feed speed can cause longer diffusion paths for the hydrogen into the crack-critical areas. In addition, a changed direction of solidification of weld metal is possible with deeper penetration which can influence the hydrogen diffusion in terms of preferred direction and therefore time [58]. Consequently, TTF of the implant specimens increases significantly.…”

Section: Discussionmentioning

confidence: 99%

Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

et al. 2020

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High-strength structural steels are used in machine, steel, and crane construction with yield strength up to 960 MPa. However, welding of these steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of microstructure, local stress/strain, and local hydrogen concentration. In addition to the three main factors, the used arc process is also important for the performance of the welded joint. In the past, the conventional transitional arc process (Conv. A) was mainly used for welding of high-strength steel grades. In the past decade, the so-called modified spray arc process (Mod. SA) has been increasingly used for welding production. This modified process enables reduced seam opening angles with increased deposition rates compared with the Conv. A. Economic benefits of using this arc type are a reduction of necessary weld beads and required filler material. In the present study, the susceptibility to HAC in the heat-affected zone (HAZ) of the high-strength structural steel S960QL was investigated with the externally loaded implant test. For that purpose, both Conv. A and Mod. SA were used with same heat input at different deposition rates. Both conducted test series showed same embrittlement index “EI” of 0.21 at diffusible hydrogen concentrations of 1.3 to 1.6 ml/100 g of arc weld metal. The fracture occurred in the HAZ or in the weld metal (WM). However, the test series with Mod. SA showed a significant extension of the time to failure of several hours compared with tests carried out with Conv. A.

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Section: Discussionmentioning

confidence: 99%

Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

et al. 2020

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“…This chemical element is a factor with significant impact on the properties of welded joints. A phenomenon of hydrogen embrittlement is characteristic for low-carbon structural steel also in the air [28,29]. This type of embrittlement can occur even with the cathodic protection conditions [30].…”

Section: Introductionmentioning

confidence: 99%

Underwater In Situ Local Heat Treatment by Additional Stitches for Improving the Weldability of Steel

Tomków

Janeczek

2020

Applied Sciences

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In this paper the influence of in situ local heat treatment performed by additional stitches on the weldability of high-strength low-alloy (HSLA) S355J2C+N steel was tested. The investigated steel is characterized by high susceptibility to cold cracking. It is necessary to find a method to improve the quality of welded joints. The local heat treatment was applied as an effect of bead-on plate welding made on the face of a Tekken test joint. The specimens were made by the use of covered electrodes in the water environment. For testing weldability, Tekken test specimens were made. Then, the different number of the pad welds with different overlapping were laid on the face of the tested welds. Non-destructive (NDT) visual and penetrant tests were undertaken. During the NDT, imperfections like shape mistakes and spatters were found. Then, metallographic macro- and microscopic testing were performed. The macroscopic observations proved that water environment can generate imperfections like cracking and pores. However, for specimens with additional stitches the number of imperfections decreased. Microscopic tests proved that the proposed technique affected the structure of the heat-affected zone (HAZ). The specimens without the application of additional stitches are characterized by brittle bainitic and martensitic structure. Specimens, in which the additional stitches were applied, contain tempered martensite, fine ferrite and fine pearlite in their HAZ. It was also observed that the number of cracks decreased for in situ local heat-treatment specimens. The final step was Vickers HV10 hardness measurement. These measurements confirmed previous results. The heat from additional stitches affected the steel by significantly decreasing the hardness by 80–100 HV10. The results of experiments showed that the heat from pad welds provided microstructural changes in heat-affected zones and a decrease in the susceptibility to cold cracking, which results in improvement in the weldability of HSLA steel in wet welding conditions.

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“…Temperature dependence of diffusion where "D 0 " is a material-specific constant, "D" is the temperature dependent diffusion coefficient, and the exponential factor is the Boltzmann factor with "E A " as activation energy for diffusion (in kJ/mol), "R" is the universal gas constant (8.3145 J/mol*K), and "T" is the absolute temperature in K. Diverse diffusion coefficients are available in literature for low alloyed Cr-Mo(-V) steels [10,13,[18][19][20][21]. They are used, e.g., for DHT-recommendations (temperature and holding times [22][23][24][25][26]). Diffusion coefficients for 9% Cr steels are limited [10,[26][27][28][29] in particular for the weld metal (WM).…”

Section: Hydrogen Diffusion In 9% Cr Steelsmentioning

confidence: 99%

“…They are used, e.g., for DHT-recommendations (temperature and holding times [22][23][24][25][26]). Diffusion coefficients for 9% Cr steels are limited [10,[26][27][28][29] in particular for the weld metal (WM). Table 1 shows selected minimum and maximum diffusion coefficients of low-and high-alloyed Cr-Mo steels.…”

Section: Hydrogen Diffusion In 9% Cr Steelsmentioning

confidence: 99%

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Thickness and microstructure effect on hydrogen diffusion in creep-resistant 9% Cr P92 steel and P91 weld metal

et al. 2021

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Martensitic 9% Cr steels like P91 and P92 show susceptibility to delayed hydrogen assisted cracking depending on their microstructure. In that connection, effective hydrogen diffusion coefficients are used to assess the possible time-delay. Limited data on room temperature diffusion coefficients reported in literature vary widely by several orders of magnitude (mostly attributed to variation in microstructure). Especially P91 weld metal diffusion coefficients are rare so far. For that reason, electrochemical permeation experiments had been conducted using P92 base metal and P91 weld metal (in as-welded and heat-treated condition) with different thicknesses. From the results obtained, diffusion coefficients were calculated using to different methods, time-lag, and inflection point. Results show that, despite microstructural effects, the sample thickness must be considered as it influences the calculated diffusion coefficients. Finally, the comparison of calculated and measured hydrogen concentrations (determined by carrier gas hot extraction) enables the identification of realistic diffusion coefficients.

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Hydrogen diffusion in creep-resistant 9% Cr P91 multi-layer weld metal

Cited by 8 publications

References 44 publications

Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

Underwater In Situ Local Heat Treatment by Additional Stitches for Improving the Weldability of Steel

Thickness and microstructure effect on hydrogen diffusion in creep-resistant 9% Cr P92 steel and P91 weld metal

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