Cladding of Ni-alloy UNS N08825 in pressure vessel ......cladding has a major effect on the cost of the vessel production. Per-forming Ni-alloy overlay cladding in a controlled manner

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546 Rivista Italiana della Saldatura • 4 • Luglio / Agosto 2017

Biryulin Denis,Esab Saldatura, [email protected].

Strip overlay cladding of Ni-alloys is one of the most cost sensitive applications in pressure vessel fabrication. Compared with clad-ding of austenitic alloys, Ni-alloy cladding has a major effect on the cost of the vessel production. Per-forming Ni-alloy overlay cladding in a controlled manner is essential to meet cost targets and optimize efficiencies. The cladding consum-ables, the actual cladding proce-dure and the equipment used are critical process parameters for fabricators seeking success in this application.The following key factors affecting cost efficiency will be discussed:• The cladding process (elec-

tro-slag or submerged arc) used.

• Total overlay thickness applied. • Optimization of bead overlaps.• Control of dilution to achieve

the technical requirements.• Productivity of the methods

used.This paper will discuss single and double layer cladding and the suitability against actual require-ments for Ni-base clad layers of alloy UNS N08825 / EQ NiFeCr-1 on both P355NL1 and CrMo steels.

1. INTRODUCTION

Application of Ni-base corrosion resistant overlay is one of the most cost sensitive applications in pres-sure vessel fabrication. Compared with, for example, austenitic alloy overlay, Ni-one has bigger effect on the overall cost of the vessel production. Therefore, it is that im-portant to perform Ni-overlay in a controlled way to ensure the effi-ciency of the process and the cost of it. From this perspective not only

Cladding of Ni-alloy UNS N08825 in pressure vessel applications: optimized efficiency with a complete solution

the right choice of cladding con-sumables but also used cladding procedure and equipment (power source) are essential and should be taken into account by fabrica-tors.First of all, it is worth to mention that there are a number of ways to apply internal corrosion resist-ant lining of the pressure vessel: weld, roll bond and explosive bond cladding. With this being said, weld cladding still is preferred to be used in most applications while in some cases usage of other meth-ods are not even recommended (e.g. use of roll bond clad for pres-sure vessel base material thick-nesses > 100 mm).When weld strip cladding (or sim-ply “strip cladding” hereafter) is used, the following key factors will ultimately effect the cost efficiency of Ni-alloy cladding:• The cladding process (elec-

tro-slag or submerged arc) used.

• Total overlay thickness.• Productivity (in m2/hour).• Amount of cladded material

lost in overlaps.• Percentage of dilution with

base material.Apart from the above, the factors like cladding speed and repair rate of the applied clad layer are also to be considered by a manufactur-er in order to achieve the desired productivity level and, as a result, to bring down the overall produc-tion cost.All the factors above can be ad-dressed not only through the careful choice of cladding con-sumables: strip and, most impor-tantly, flux. Well-designed, proved welding procedure and cladding



equipment (first of all, a power source) also play an important role in control of the mentioned fac-tors. Overall, total package solution (strip/flux + cladding procedure + equipment) are to be looked at to ensure good control over the pro-duction costs when cladding.Overlay thickness is one of the main drivers for the overall clad-ding cost. The thinner the overlay the less expensive it will be. Therefore, in this paper the focus is made on this specific aspect.Depending on the application, de-signer and manufacturer’s experi-ence, an 825 alloy overlay can be built in 1 or 2 layers. The current paper is considering both cases.

2. ESW vs SAW

825 clad overlay can be obtained with either SAW or ESW cladding process. Due to high dilution with base metal determined by electric arc presence in the process, SAW

normally requires 2 or, sometimes 3 layers to obtain required chem-istry in the overlay. At this respect ESW, due to much lower dilution (approximately half compared with SAW), is more preferable to use as it allows to clad in single layer which is not possible to do with SAW. If required, 2 layers are also applicable with ESW but this can be done with much higher speed than with SAW and thus, higher productivity (Figure 1). This makes up the choice of ESW in preference to SAW even when the overlay is to be clad with 2 layers.

3. Obtaining 825 overlay with high speed ESW in 2 layers

3.1 Overlay requirements

The key requirement from the cus-tomer was to obtain 825 overlay using neutral flux only.The main customer’s objective is to obtain as minimum as it possi-

ble thickness of the overlay which should meet the requirements be-low.Typical requirement for corrosion resistant overlay is to obtain alloy 825 (UNS N08825) chemistry at the level of 3 mm from the top of the cladding surface.Non Destructive Examination (NDE) like ultrasonic (UT) and pen-etrant (PT) examinations are to be performed:• UT on the top of the 2nd layer

after 610 °C x 14 h PWHT• PT on the 1st layer at AW condi-

tion and on the 2nd layer at AW and after 610 °C x 14 h PWHT.

Guided side bend test: 4 x trans-verse specimens and 4 x longitu-dinal specimens. Both after 610 °C x 14 h PWHT.Hardness of base metal HAZ be-neath overlay to be measured and be < 248 HV10. This requirement is typical for pressure vessels oper-ating in sour (H2S containing) ser-vice.

3.2 ESW cladding procedure qualification

In order to fulfil customer’s require-ments above the flux/strip combi-nation in Table 1 was chosen: ESW cladding was performed on 50 mm C-Mn plate – see testing condi-tions’ summary (Table 2).In Ni-base cladding, it is not only properly done welding parameter settings but also setting of proper stick-out, flux height and position of steering magnets play signifi-cant role and have a big impact on achieving the good result (Figure 2). It is especially true when clad-ding Ni-base strips of 0,5 x 90 mm.After a number of pre-trials aiming to achieve as thin as it possible 825 overlay thickness obtained in 2 layers, the optimum parameter settings have been found (Table 3).As the fusion line is showing not a flat profile (Figure 3 and 4), the overlay thickness has a range, as indicated in the column to the far right in Table 3.Figure 1 - Productivity (m2/h) comparison ESW vs SAW.

OK Flux 10.11 OK Band NiFeCr1

Neutral flux for single and multilayer ESW cladding of Ni-base and high, full

austenitic type strip grades.EN ISO 14174: ES A FB 2B 56 44 DC

Basicity index: 5.4Density: ~ 1,0 kg/dm3

Grain size: 0,2-1,0 mmSlag type: very high basic

Nickel-iron-chromium welding strip with small quantities of molybde-

num, copper and titanium. The weld deposit chemistry corresponds to UNS

N08825 (so called Alloy 825).EN ISO 18274 - B Ni 8065

(NiFe30Cr21Mo3)SFA/AWS A5.14 - EQNiFeCr-1

Table 1 - Consumables.



Test number 4312: strip dimensions 60x0,5 mm4460: strip dimensions 90x0,5 mm

Project 825, ESW 2 layers strip cladding

Process ESW

Equipment Cladding head: ESW 90; power sources: 2 x LAF1601 (parallel connection)

Consumables1. OK Band NiFeCr1 (825 strip), dimensions 60x0,5 mm2. OK Band NiFeCr1 (825 strip), dimensions 90x0,5 mm

3. OK Flux 10.11

Base material P355NL1, thk 50 mm

PWHT conditionsHeating rate: 55 °C/hour (free up to 300 °C)

Holding temperature/time: 610 ± 15 °C/14 hours Cooling rate: 55 °C/hour (free under 300 °C)

Table 2 - ESW 825 cladding test conditions summary (2 layers). Further increase of cladding speed with an aim to further reduce over-lay thickness did not show stability of ESW cladding process, so it was decided to not go this direction.Chemical composition was analyz-ed at the level of 3 mm from the top of the cladding surface, reveal-ing results meeting alloy 825 (UNS N08825) chemistry requirements (Table 4). The only exceptions are Ti% and Si% values which are out-side of the required chemistry but this deviation is commonly accept-ed by the customers.Test results of NDE (Table 5), Bend test (Table 6) and Hardness test (Table 7) have reviled no issues in the clad weld deposit. For ref-erence purposes, hardness were measured not only in base metal HAZ beneath clad overlay but also in base metal and in overlay itself. All hardness results (including HAZ ones) are < 248 HV10 (< 240 HB30) as required by the customer speci-fication – see results in Table 7. As a conclusion, the solution has been found to obtain minimum possible

Test Layer Strip width (mm)

Current(A)

Voltage(V)

Speed(cm/min)

Overlay thickness(mm)

4312 1st 60 1250 24 30 3,0÷4,0

4312 1st & 2nd 60 1250 24 30 6,0÷7,0

4460 1st 90 1800 24 30 3,0÷4,0

4460 1st & 2nd 90 1800 24 30 6,0÷7,0

Note: Stick-out 25 mm – Flux Height 20 mm.

Table 3 - Parameters settings and obtained overlay thickness.

Figure 2 - Cladding head and magnets position.

Figure 3 - Thickness of the 1st & 2nd layer. Figure 4 - Thickness of the 1st layer.



thickness of 6,0-7,0 mm for 2 lay-er ESW cladding to get 825 alloy overlay and it has been proved to meet customer’s requirements.Productivity and strip/flux con-sumption summary for the 2 layer ESW 825 cladding (Table 8). The table shows obvious productivity

C Si P S Ni Cr Mo Mn Ti Cu Al Fe

Strip(Heat:537566) 0,014 0,28 0,013 0,005 43 22,5 2,98 0,56 0,97 2,17 0,16 27,6

Overlay(60x0,5 mm) 0,018 0,89 0,013 0,003 42 21,9 2,92 0,54 0,13 2,15 0,04 29,6

Overlay(90x0,5 mm) 0,025 0,91 0,014 0,006 42 21,6 2,90 0,55 0,12 2,14 0,04 30,3

RequirementAWS/SFA 5.14:

EQNiFeCr-1< 0,05 < 0,50 < 0,03 < 0,03 38-46 19,5-23,5 2,3-3,5 < 1,0 0,6-1,2 1,5-3,0 < 0,20 > 22

Table 4 - Chemical analysis of the ESW weld overlay (%) at 3 mm below the surface of 2nd layer.

NDT summary

Test n. Test method Test standard Test location Weld overlay condition Result

4312 PT ASME IX/ASME VIII D2 7.5.8 1st layer As welded Acceptable

4312 PT ASME IX/ASME VIII D2 7.5.8 2nd layer As welded Acceptable

4312 PT ASME IX/ASME VIII D2 7.5.8 2nd layer PWHT Acceptable

4312 UT ASME SA 578 2nd layer PWHT Acceptable

4460 PT ASME IX/ASME VIII D2 7.5.8 1st layer As welded Acceptable

4460 PT ASME IX/ASME VIII D2 7.5.8 2nd layer As welded Acceptable

4460 PT ASME IX/ASME VIII D2 7.5.8 2nd layer PWHT Acceptable

4460 UT ASME SA 578 2nd layer PWHT Acceptable

Table 5 - NDE summary.

increase (by 50%) and also con-sumables cost savings (by 3,5%) due to reduction of material losses in overlaps when switching from 60x0,5 mm to 90x0,5 mm strip. The savings will be particularly visible when pressure vessel area is to be clad.

Bend test: test standard ASME IX, ed. 2015 (tested in PWHT conditions)

Test n. Type Thickness (mm)

Former diameter

(mm)

Distance rollers (mm)

Bend Angle

(°)Results Com-

ment

60 mm, PWHT SBT 10 40 63,2 180 Accep-

tableNo re-marks

60 mm, PWHT SBL 10 40 63,2 180 Accep-

tableNo re-marks

90 mm, PWHT SBT 10 40 63,2 180 Accep-

tableNo re-marks

90 mm, PWHT SBL 10 40 63,2 180 Accep-

tableNo re-marks

Note: SBT: Side Bend Transverse, SBL: Side Bend Longitudinal.

Table 6 - Bend test summary.

4. Obtaining 825 overlay in 1 layer

4.1 Overlay thickness restriction factors

As it was mentioned in Clause 2 of the current paper, the typical requirement for corrosion resistant overlay is to obtain alloy 825 (UNS N08825) chemistry at the level of 3 mm from the top of the cladding surface. So, the main challenge when qualifying 825 overlay ob-tained in 1 layer is, from one hand, to achieve overlay thickness as thin as it possible, on the other hand deliver 825 alloy chemistry at 3 mm below the top surface. This ob-jective is getting especially difficult to achieve taking into account the fact that fusion line of clad deposit and base metal does not normal-ly have flat profile which leads to



Hardness test: EN ISO 6506-1

Test number Location Single values (HV10) Average Measurement uncertainty

60 mm, PWHT 1st layer 169 175 169 171 ± 3.5%

60 mm, PWHT 2nd layer 180 180 177 179 ± 3.5%

60 mm, PWHT HAZ 174 180 176 177 ± 3.5%

60 mm, PWHT BM 163 163 169 165 ± 3.5%

90 mm, PWHT 1st layer 156 160 156 157 ± 3.5%

90 mm, PWHT 2nd layer 160 159 161 160 ± 3.5%

90 mm, PWHT HAZ 191 186 189 189 ± 3.5%

90 mm, PWHT BM 164 158 161 161 ± 3.5%

Table 7 - Hardness test summary.

High speed ESW 2 layers


Strip width (mm) 60 90

# layers 2 2

Cladding speed (cm/min) 30 30

Strip feed speed (cm/min) 160 150

Overlay thk (mm) 6.5 6.5

Productivity (m2/h) 0,54 0,81

Productivity (kg/h) 23 33

# Overlap/m2 31 20

Material losses in overlap (kg/m2) 4 3

Strip consumption (kg/m2) 57 55

Flux consumption (kg/m2) 34 33

Note: overlap is 5 mm.

Table 8 - ESW 825 productivity & consumption summary (2 layers).

overlay thickness variations up to 0,7 mm (Figure 5). Another factor which should be considered when optimum overlay thickness is to be defined is diffusion effect that hap-pens when heterogeneous fusion takes place in the base metal & clad Ni-alloy metal interface. Ener-gy-dispersive X-ray spectrometry (EDX) analysis reviles that diffusion of alloying elements from overlay into base metal and iron from base metal into weld metal takes place at the distance of approximately 0,4-0,5 mm from fusion line (for carbon steel & 825 alloy).

The diffusion area/depth is deter-mined by both type of base mate-rial and clad metal and does not depend on welding parameters (Figures 6 and 7).Both factors (irregular fusion line profile and diffusion effect) define the overlay thickness where clad metal can be considered as being homogeneous and thus, clad met-al chemical composition can be guaranteed. Therefore, taking into account thickness variations due to irregu-lar fusion line (up to 0,7 mm) and diffusion area (about 0,5 mm), we can state that beyond 1,5 mm distance from fusion line, to be on the safe side, homogeneous clad

Figure 5 - Variations of thickness in ESW 825 clad overlay.



Figure 6 - EDX line analysis: 825 ESW cladding, 24 cm/min.

Figure 7 - EDX line analysis: 825 ESW cladding, 30 cm/min.

metal having uniform chemical composition is to be obtained for the given base metal and clad metal types (carbon steel and 825 alloy clad metal).

4.2 Obtaining 825 overlay in single layer (normal speed)

Based on the above conclusion, the customer has decided to put 5,0 mm as a minimum over-lay thickness with 825 chemistry to be obtained at 3 mm below the clad overlay surface. The key requirement, as in the previous case, was to obtain 825 clad overlay with neutral flux only. Taking this key requirement into account a num-ber of pre-trail clad tests have been performed to identify the optimum parameter settings with an objective to obtain 5,0-5,5 mm overlay thickness in 1 layer using ESW cladding (Figure 6 showing self-lifting slag of 90x0,5 mm strip and Figure 7 the resulted overlay).Test conditions are provided in Table 9.The found parameter settings and resulted chem-istry at the level of 3 mm from the top surface of 1 layer 825 cladding are presented in Table 10 and Table 11 correspondingly.NDE, bend test and hardness tests have been performed with the results shown in Tables 12-14.The above shows that ESW 825 cladding with 90x0,5 mm strip provides overlay that is on the low end of the customer’s thickness require-ment, meets 825 alloy chemical composition at 3 mm below surface and fulfils other tests’ re-quirements.

Figure 8 - Self-lifting slag of ESW clad with OK Band NiFeCr1 (90 mm)/OK Flux 10.11. Figure 9 - 825 overlay done in 1 layer ESW.



Test conditions summary

Test 825, ESW 1 layer strip cladding

Test number

4966: Strip dimensions 90x0,5 mm, subjected to PWHT 655 °C /8 h 4967: Strip dimensions 90x0,5 mm, subjected to PWHT 655 °C /28 h

Process ESW


Consumable 1. OK Band NiFeCr1 (825 strip), dimensions 90x0,5 mm2. OK Flux 10.11

Base material SA 387 P22/10CrMo9-10, thk 50 mm

PWHT conditions

1. (Test n. 4966)- Heating rate: 55 °C/hour (free up to 300 °C)- Holding temperature/time: 655 ± 10 °C/8 hours- Cooling rate: 55 °C/hour (free under 300 °C)


Testing scope

1. 100% PT Examination, acc. to ASME IX 2. 100% UT Examination, acc. to ASME SA-578 3. Transverse Hardness survey (WM+HAZ+BM), HV10, ISO

6507-14. 4x Side bend transverse, ASME IX/AWS B4.0-2007 5. Chemical analysis located at 3 mm subsurfaceNote: All tests performed in PWHT conditions

Table 9 - ESW 825, 90x0,5 mm test conditions summary (single layer).

Productivity and strip/flux con-sumption of ESW 825 single layer vs 2 layers are the following (Table 15). As it can be seen from the ta-ble above, switching from 2 layers to single layer ESW cladding even

Test n. Current(A)

Voltage (V)

Speed (cm/min)

Heat input (kJ/mm)

Overlay thickness

(mm)

4966, 4967 1800 25 17 15,9 5,0÷5,5

Nota: stick-out 25 mm.

Test n. C Si P S Ni Cr Mo Mn Ti Cu Al Fe

Strip 90x0,5 mm

(Heat: 537566)0,014 0,28 0,013 0,005 43 22,5 2,98 0,56 0,97 2,17 0,16 27,6

Overlay 3 mmsubsurface 4966, 4967

0,027 0,94 0,014 0,009 40 21,1 2,87 0,5 0,1 2,06 0,03 32,7


EQNiFeCr-1< 0,05 < 0,50 < 0,03 < 0,03 38-46 19,5-23,5 2,3-3,5 < 1,0 0,6-1,2 1,5-3,0 < 0,20 > 22

Table 10 - ESW 825, 90x0,5 mm parameters settings and obtained overlay thickness.

Table 11 - Chemical analysis of clad overlay (%) at 3 mm below the surface (single layer).

if the cladding speed is sacrificed still give 14% increase in productiv-ity and 22%/21% reduction in strip/flux consumption. Both factors will positively influence cost reduction – increased productivity will drive

reduction of production costs while consumables consumption decrease will bring down costs of welding consumables per square meter and, correspondingly, per clad pressure vessel.

4.3 Obtaining 825 overlay in single layer (high speed)

Despite of obvious improvement in both production and consuma-bles cost reduction cladding with single layer vs 2 layers, it has been realized that there is still a room for further improvement. Being locked within the min 5,0 mm overlay thickness requirement from an-other customer, the work has been continued to further optimize the parameters and thus, improve pro-ductivity using ESW 825 cladding with single layer. As above, the key requirement was to obtain 825 clad overlay with neutral flux only.The following trials have been car-ried out – see the test conditions and scope: in Table 16.The following optimized parame-ters have been found (Table 17).The visual inspection has revealed even bead profile (Figure 10), smooth inter-bead transition and overlaps with no appearance of ridges (Figure 11). No surface de-fects. The resulted 825 overlay was tested with the following results (Tables 18-21).All test results obtained with ESW 825 optimized cladding parame-ters are meeting the customer’s requirements. The following param-eter optimization have been also



NDT Summary

Test n. Test method Test standard Test location Treatment condition Result

PWHT 655 °C/8 h PT ASME IX 100% overlay surface area PWHT Acceptable

PWHT 655 °C/8 h UT ASME SA 578 100% overlay surface area PWHT Acceptable

PWHT 655 °C/8 h PT ASME IX 100% overlay surface area PWHT Acceptable

PWHT 655 °C/28 h UT ASME SA 578 100% overlay surface area PWHT Acceptable

Table 12 - ESW 825, 90x0,5 mm NDE summary.

Bend test: test standard ASME IX, edition 2015/AWS B4.0-2007 (tested in PWHT conditions)

Test n. Type Thickness (mm)

Former diameter (mm)

Distance rollers (mm)

Bend Angle (°) Results Comment

PWHT 655 °C/8 h SBT 10 40 63,2 180 Acceptable No remarks

PWHT 655 °C/28 h SBT 10 40 63,2 180 Acceptable No remarks

Note: SBT: Side Bend Transverse

Table 13 - ESW 825, 90x0,5 mm bend test summary.

Hardness test: ISO 6506-1

Location Single values (Hv10) Average Measurement uncertainty

PWHT 655 °C/8 h WM 165 162 164 164 ±3.5%

PWHT 655 °C/8 h HAZ 227 222 226 225 ±3.5%

PWHT 655 °C/8 h BM 161 160 159 160 ±3.5%

PWHT 655 °C/28 h WM 260 277 275 271 ±3.5%

PWHT 655 °C/28 h HAZ 232 232 229 231 ±3.5%

PWHT 655 °C/28 h BM 171 169 175 172 ±3.5%

Table 14 - ESW 825, 90x0,5 mm hardness test summary.



ESW single layer

Strip width (mm) 60 90 90

# layers 2 2 1

Cladding speed (cm/min) 30 30 17

Strip feed speed (cm/min) 160 150 150

overlay thk (mm) 6,5 6,5 5,0

Productivity (m2/h) 0,54 0,81 0,92

Productivity (kg/h) 23 33 33

# Overlap/m2 31 20 10

Material losses in overlap (kg/m2) 4 3 2

Strip consumption (kg/m2) 57 55 43

Flux consumption (kg/m2) 34 33 26

Note: overlap is 5 mm.

Table 15 - ESW 825, productivity & consumption (single vs 2 layers).



done with 90x0,5 mm strip – see the test conditions and scope in Table 22. In Tables 23 and 24 are presented parameters used and chemical composition of the ob-tained 825 overlay.

Test conditions summary

Test 825, ESW 1 layer high productivity solution, overlay thickness 5,0-5,5 mm

Test number 5570: Strip dimensions 60x0,5 mm, subjected to PWHT 620 °C/3,5 h 5571: Strip dimensions 60x0,5 mm, subjected to PWHT 620 °C/5x3,5 h

Process ESW


Consumables 1. OK Band NiFeCr1 (825 strip), dimensions 60x0,5 mm2. OK Flux 10.11

Base material P355NL1 (SA516 Gr. 60), thk 50 mm

PWHT conditions

1. (Test n. 5570) Thermal cycle:- Heating rate: 55 °C/hour (free up to 300 °C)- Holding temperature/time: 620 ± 10 °C/3,5 hours- Cooling rate: 55 °C/hour (free under 300 °C)

2. (Test n. 5571) Thermal cycle (cycle repeated 5 times, providing total holding time 17,5 h @ 620 °C)- Heating rate: 55 °C/hour (free up to 300 °C)- Holding temperature/time: 620 ± 10 °C/3,5 hours- Cooling rate: 55 °C/hour (free under 300 °C)

Testing scope

1. Optimization of process meeting requirements in overlay 5,0-5,5 mm2. 100% PT Examination, acc. to ASME IX, in PWHT conditions3. 100% UT Examination, acc. to ASME SA-578, in PWHT conditions4. Transverse Hardness survey (WM+HAZ+BM), Hv10, ISO 6507-1:20065. 4x Side bend transverse, ASTM E190-92: 2008, in PWHT conditions6. Chemical analysis located at 3 mm from the top of the surface

Table 16 - ESW 825 cladding with optimized parameters (single layer): test conditions summary.

Test n. Current (A)

Voltage (V)

Speed (cm/min)

Heat input (kJ/mm)

Overlay thickness (mm)

5570/5571 1660 25 27 9,2 5,0÷5,5

Note: stick-out 25 mm.

Table 17 - Optimized parameters for ESW 825, 60x0,5 mm cladding (single layer).

Analysis scope C Si P S Ni Cr Mo Mn Ti Cu Al Fe

Strip 60x0,5 mm (Heat: 537566) 0,014 0,28 0,013 0,005 43 22,5 2,98 0,56 0,97 2,17 0,16 27,6

5570/5571 (Top surface) 0,026 0,90 0,015 0,004 39,6 20,9 2,83 0,53 0,10 1,87 0,04 33,4

5570-1 (3 mm surface) 0,021 0,89 0,015 0,003 39,5 20,8 2,85 0,51 0,13 1,86 0,05 32,6

AWS/SFA 5.14: EQNiFeCr-1 < 0,05 < 0,50 < 0,03 < 0,03 38-46 19,5-23,5 2,3-3,5 < 1,0 0,6-1,2 1,5-3,0 < 0,20 > 22

Table 18 - ESW 825 optimized parameters: chemical analysis.

Figure 10 - ESW 825: smooth overlap transition. Figure 11 - ESW 825: overlay appearance (no defect detected by VT/PT).



Hardness test: ISO 6507-1:2006

Location Single values (Hv10) Average Measurement uncertainty

PWHT 620 °C/3,5 h WM 147 155 149 150 ±3.5%

PWHT 620 °C/3,5 h HAZ 201 217 215 211 ±3.5%

PWHT 620 °C/3,5 h BM 160 162 163 162 ±3.5%

PWHT 5x620 °C/3,5 h WM 151 156 152 153 ±3.5%

PWHT 5x620 °C/3,5 h HAZ 208 210 208 209 ±3.5%

PWHT 5x620 °C/3,5 h BM 158 150 153 154 ±3.5%

NDT summary

Test method Test standard Test location Result

PWHT 620 °C/3,5 h PT ASME IX 100% overlay surface area Acceptable

PWHT 620 °C/3,5 h UT ASME SA 578 100% overlay surface area Acceptable

PWHT 5x620 °C/3,5 h PT ASME IX 100% overlay surface area Acceptable

PWHT 5x620 °C/3,5 h UT ASME SA 578 100% overlay surface area Acceptable

Bend test: test standard ASTM E190-92: 2008 (tested in PWHT conditions)

Type Thickness(mm)

Former diameter (mm)

Distancerollers (mm)

Bend angle (°) Results

PWHT 620 °C/3,5 h SBT 10 40 63,2 180 Acceptable

PWHT 5x620 °C/3,5 h SBT 10 40 63,2 180 Acceptable

Note: SBT: Side Bend Transverse.

Table 19 - ESW 825 optimized parameters: NDT summary.

Table 20 - ESW 825 optimized parameters: bend test results.

Table 21 - ESW 825 optimized parameters: hardness test.

All other tests have been per-formed with satisfactory results.Now let’s have a look at how much the cladding with optimized pa-rameters will give us in terms of productivity (Table 25).Parameter optimization led to clad-ding speed increase from 17 up to 26 cm/min (for 90x0,5 mm strip) which has given additional 52% productivity boost.

5. Conclusions

When production is in concern, ESW is the process to be selected for 825 overlay cladding of pres-

sure vessels. It has been proved that both 60x0,5 and 90x0,5 mm strip dimensions can be success-fully used without any major issues for Ni-based ESW cladding (name-ly for 825 alloy) both in 2-layer and 1-layer applications. This is despite the fact that it has been consid-ered so far that 90x0,5 mm strip cladding is not easy to perform.Switch from 60x0,5 to 90x0,5 mm strip, will give 50% boost in pro-ductivity and 3,5% consumables cost reduction due to less losses on overlap areas.When Ni-base ESW cladding is performed and there is a require-

ment to obtain as thin as it possi-ble overlay, especially when single layer is to be clad, a precaution should be made to not go too close to fusion line. Due to both diffusion effect and irregular fusion line pro-file, it is recommended to stay at about 1,5 mm from fusion line to ensure homogeneous clad met-al is obtained. Single layer ESW cladding has shown strong advan-tage over 2 layers cladding from both consumables and production costs perspective. The consuma-bles cost reduction (less kg/m2 of strip & flux are consumed) is main-ly driven by the reduction of over-lay thickness. Production costs are reduced due to less time needed to complete the overlay with single layer compared with 2 layers clad-ding. Optimized cladding parame-ters (for 90x0,5 mm), have allowed to deliver faster cladding speed as much as 26 cm/min but still fulfill-ing 5,0 mm thickness requirement, are capable to deliver 52% pro-ductivity increase compared with conventional speed in 90x0,5 mm strip. It should be noticed that all cladding tests presented in this paper, including high speed 30 cm/min and thin overlay in single layer, have been performed with neutral flux that is in preference by major pressure vessel customers.


Test n. Current (A) Voltage (V) Speed (cm/min) Heat input (kJ/mm) Overlay thickness (mm)

6234/6235 2300 25 26 13,3 5,0÷5,5

Note: see WPS for detailed parameters and settings.

Analysis scope C Si P S Ni Cr Mo Mn Ti Cu Al Fe

Strip 90x0,5 mm(Heat: 537566) 0,014 0,28 0,013 0,005 43 22,5 2,98 0,56 0,97 2,17 0,16 27,6

6234 (Top surface) 0,029 0,78 0,013 0,002 38,2 20,1 2,6 0,62 0,08 1,91 0,02 36,2

6234-1 (3 mm surface) 0,029 0,79 0,014 0,002 38,2 20,1 2,66 0,64 0,12 1,88 0,04 35,9


EQNiFeCr-1< 0,05 < 0,50 < 0,03 < 0,03 38-46 19,5-23,5 2,3-3,5 < 1,0 0,6-1,2 1,5-3,0 < 0,20 > 22



ESW single layer

High speedESW single layer

High speedESW single layer

Strip width (mm) 60 90 90 60 90

# layers 2 2 1 1 1

Cladding speed (cm/min) 30 30 17 27 26

Strip feed speed (cm/min) 160 150 150 250 230

overlay thk (mm) 6,5 6,5 5,0 5,0 5,0

Productivity (m2/h) 0,54 0,81 0,92 0,97 1,40

Productivity (kg/h) 23 33 33 37 51

# Overlap/m2 31 20 10 16 10

Material losses in overlap (kg/m2) 4 3 2 3 2

Strip consumption (kg/m2) 57 55 43 44 43

Flux consumption (kg/m2) 34 33 26 26 26

Nota: overlap is 5 mm.

Table 23 - ESW 825 cladding, 90x0,5 mm (single layer, optimized parameters).

Table 24 - Chemical analysis.

Table 25 - ESW 825 productivity & consumption (single layer; optimized parameters).

Test summary

Project 825, ESW 1 layer high productivity solution, overlay thickness 5,0-5,5 mm.

Test number 6234: Strip dimensions 90x0,5 mm, subjected to PWHT 620 °C/8 h 6235: Strip dimensions 90x0,5 mm, subjected to PWHT 620 °C/28 h

Process ESW

Consumable 1. OK Band NiFeCr1 (825 strip), dimensions 90x0,5 mm2. OK Flux 10.11

Base material SA 387 P22/10CrMo9-10, thk 50 mm

PWHT conditions


2. (Test n. 6235)- Heating rate: 55° C/hour (free up to 300 °C)- Holding temperature/time: 655 ± 10 °C/28 hours- Cooling rate: 55 °C/hour (free under 300 °C)

Testing scope

1. Optimization of process meeting requirements in overlay 5,0-5,5 mm 2. 100% PT Examination, acc. to ASME IX, in PWHT conditions 3. 100% UT Examination, acc. to ASME SA-578, in PWHT conditions 4. Transverse Hardness survey (WM+HAZ+BM), Hv10, ISO 6507-1:20065. 4x Side bend transverse, ASTM E190-92: 2008, in PWHT conditions6. Chemical analysis located at top and 3 mm below the surface

Table 22 - ESW 90x0,5 mm 825 strip cladding with optimized parameters.

Documents

Cladding of Ni-alloy UNS N08825 in pressure vessel ......cladding has a major effect on the cost of the vessel production. Per-forming Ni-alloy overlay cladding in a controlled manner