Effect of Stainless Steel Weld Overlay Deposit on the Hardness of API

5L Pipes

Adhe Aryswan

, Nurul Laili Arifin, Hanifah Widiastuti and Dois Ditya Wahyu Kirana

Mechanical Engineering, Politeknik Negeri Batam, Batam, Indonesia

Keywords: Weld Overlay, Vickers Hardness, Corrosion Resistant Alloys.

Abstract: To improve the corrosion resistance of API 5 L pipe, we applied a weld overlay of UNS S31603 stainless steel

as filler metal. To confirm the modified material’s quality, we determine the hardness of the material to be

compared to API 5LD specification. We performed Vickers hardness tests at the corrosion-resistant alloy

(CRA) area and the base metal and heat-affected zone. The tests show that the deposition improves the material

hardness by 7.32%. The average Vickers hardness number at the CRA area was 212.32 HV, with 230 HV.

Referring to API 5LD qualification, the maximum hardness allowed at the CRA area is 300 HV. Thus, the

material processed by weld overlay has an acceptable quality.

1 INTRODUCTION

One of the most advantageous ways to transport oil

and natural gas to date is by pipeline due to its low

cost and large capacity (Zhou et al., 2016). Line pipes

are predominantly controlled by API 5L, which is

now also an ISO specification (ISO 3183), regulating

their manufacturing, testing, and classification

(Singh, 2017). However, the corrosive impurities like

water, hydrogen sulfide, and carbon dioxide during

extraction cannot be completely removed during

processing and transportation (Li et al., 2017). These

impurities could potentially cause material

deterioration due to serious corrosion damages

(Obanijesu, 2009). Switching the materials to the one

with higher resistance to corrosion is not considered

a possible solution since they generally possess lower

strength.

A possible solution to provide a material that

possesses high strength and corrosion resistance is to

perform the weld overlay with metallurgically

compatible corrosion resistant alloy to clad the steel

(Kannan and Murugan, 2006). The term weld

overlay, also known as weld cladding, is a method to

improve properties of a base metal by applying a

relatively thick layer of dissimilar weld metal (Rao,

Reddy, and Nagarjuna, 2011). Austenitic stainless

steels (ASS) are well known for their great corrosion

resistance (Gupta and Birbilis, 2015; Lapechenkov et

al., 2020) and are proven to be successfully added to

high strength low alloy steel (Rao, Reddy, and

Nagarjuna, 2011). Hence, they are good candidates to

be applied by weld overlay in this study. Lima et al.,

2020 reported that samples cladded by GTAW-

hotwire show an impressive corrosion resistance.

Nevertheless, after the steel is cladded, its

physical properties also change. Therefore, it is

required to investigate whether the fabricated

material still meets the standard's qualifications. One

significant property of materials directly related to its

lifetime is hardness (Lewis et al., 2019). Hardness

measurement is a mandatory step in manufacturing

many products, and one of the standard hardness tests

is Vickers (Daemi, Tomkowski, and Archenti, 2020).

This study reported a weld overlay by depositing

austenitic stainless steel on API 5L pipe by the

GTAW process. The fabricated material was then

examined by the Vickers hardness tests to ensure that

the resulting material has still complied with API

5LD specification, a standard for seamless and

welded clad steel pipe with enhanced corrosion-

resistant properties (American Petroleum Institute,

2015). It is shown that the resulting material could

meet the related standard. Hence, the weld overlay

proposed in this study could be performed on

pipelines to improve their resistance against

corrosion.

Aryswan, A., Ariﬁn, N., Widiastuti, H. and Kirana, D.

Effect of Stainless Steel Weld Overlay Deposit on the Hardness of API 5L Pipes.

DOI: 10.5220/0010352801190123

In Proceedings of the 3rd International Conference on Applied Engineering (ICAE 2020), pages 119-123

ISBN: 978-989-758-520-3

119

2 MATERIALS AND METHODS

2.1 Base Metal

Specimens was prepared in accordance with API 5L

specification. Seamless pipes was used as base metal,

with specification API 5L Gr.L450Q PSL 2, P-No 1

Gr. No 2, thickness 8.18 mm, outside diameter 219.1

mm (8” NPS), heat number J7K5650, length 1000

mm, heat treatment condition: quenched and

tempered, chemical composition (%): C = 0.06; CE

(PCM) = 0.14; CE (IIW) = 0.31. Weld overlay length

= 1000 mm.

2.2 Filler Metal

Filler metal applied in this study was austenitic

stainless steel (ASS) UNS S31603. The welding

process used two variant of filler metal, namely:

 Daiko ER309LMo size 1.2 mm with

specifications EN ISO 14343-A: G 23 12 2 L

AWS A5.9 (ER309LMo) modified, heat

number: 547158, SFA-5.9, F-No.6, A-No.8.

 Novametal ER316L size 1.2 mm with

specifications ASME II PART C: SFA-5.9

AWS A5.9/A5.9: ER316L EN ISO 14343-A:

19 12 3 L, heat number: 59583, SFA-5.9, F-

No.6, A- No.8.

The elemental contents of base metal and filler

metals can be seen in the following Table 1, while the

mechanical properties in Table 2.

The weld overlay application was illustrated in the

following Figure 1, with filler metal Daiko 309LMo

as the inner first layer and Novametal 316L as the

outer one.

Table 1: Elemental contents of materials.

Elemental

Contents

(%)

Material

Base

Metal

Daiko

309LMo

Novametal

316L

C 0.06 0.0009 0.010

Si 0.21 0.300 0.310

Mn 1.24 1.430 1.940

P 0.007 0.018 0.019

S 0.001 0.004 0.009

Cu 0.01 0.087 0.140

Cr 0.17 21.240 18.540

Ni 0.02 14.740 11.800

Mo 0.01 2.570 2.580

Table 2: Mechanical properties of materials.

Mechanical

Properties

Base

Metal

Daiko

309LMo

Novametal

316L

Tensile Strength

(MPa)

581 600 510

Yield Strength (MPa) 506 430 320

Elongation (%) 34 35 25

Impact Energy (J) N/A 100 80

2.3 Welding Process

Welding process was conducted by DCEN pulsed gas

tungsten arc welding (GTAW) without hot wire. The

welding position was 1G, with the pipe placed

horizontally and rotated counterclockwise. Welding

travel was performed step-back and moved around

2.8 – 3.6 mm. The tungsten was 3.2 mm EWLa-2type,

and the welding machine was Fronius 4500A. The

welding parameters were carried out according to

PQR shown in Table 3.

The weld overlay application was illustrated in the

following Figure 1, with filler metal Daiko 309LMo

as the inner first layer and Novametal 316L as the

outer one.

2.4 Vickers Hardness Tests

The examination performed by Vickers hardness

tester Mitutoyo model HV-113 S/N 500041203, with

diamond indenter (face angle 136

), and load 10 kgf.

The method used in this study complies with ASTM

E92 (ASTM International, 2017), that is a standard

method for testing Vickers's hardness of a metallic

material. This study conducted a Vickers hardness

test on two specimens, following the code that refers

to ASME Section IX Qualification (American

Society of Mechanical Engineers, 2010). Each of

them tested at specific test location points based on

API 5LD specification for CRA Clad or Lined Steel

Pipe (American Petroleum Institute, 2015), and

Aramco Drawing AB-036386, respectively. Those

points are illustrated in the following Figure 2 and

Figure 3.

Figure 1: Weld overlay layout.

ICAE 2020 - The International Conference on Applied Engineering

120

Table 3: Welding parameters.

Weld

Pass/

Layer

Process, Current

Type, Polarity

Filler Metal

Amps

Range (A)

Volts Range

(V)

Travel Speed

(mm/min)

Preheat and

Interpass

(°C)

Heat Input

(kJ/mm)

Classification

Size

(mm)

Speed

Range

Min Max

Layer 1 GTAW/DCEN ER309LMo 1.2 2 × 1000 190 – 230 13.1 – 14.5 400 32 – 160 0.37 0.50

Layer 2 GTAW/DCEN ER316L 1.2 2 × 1300 200 – 240 12.5 – 13.5 400 40 – 178 0.38 0.49

As shown in the previous Figure 2, the test

consists of 5 lines and each line was composed of 4

points, specifically: No. 1 at layer 1, No. 2 at HAZ,

No. 3, and No. 4 at base metal. Figure 2 also shows

the distances among lines. Those points out where the

exact positions are. However, each line is 13 mm

apart. Layer 1 and fusion line are 1 mm apart, the

same as fusion line and HAZ.

Specimen 2 was tested by 5 lines with 4 points

each, as shown in Figure 3. The points No. 1 located

at layer 2, No. 2 at layer 1, No. 3 at HAZ, and No. 4 at

base metal. The distances of lines and points, as

shown in Figure 3, are similar to Figure 2, except the

distance between fusion line and HAZ is a maximum

0.2 mm apart. Acceptance criteria of the examination

were obtained from API 5LD specification

(American Petroleum Institute, 2015) that covers the

cladded API 5L pipe qualifications. The hardness test

requirements are shown in Table 4.

Figure 2: Specific test location points of specimen 1 based

on API 5LD specification for CRA Clad or Lined Steel

Pipe.

Figure 3: Specific test location points of specimen 2 based

on Aramco Drawing AB-036386.

Since austenitic stainless steel was used as filler

metals in this study, the maximum HV allowed at the

CRA area is 300 HV10, while the hardness measured

at base metal and HAZ area should be less than 248

HV10. The number 10 following HV scale represents

the applied test force of 10 kgf (ASTM International,

2017).

3 RESULTS AND DISCUSSION

Data collected from the Vickers hardness test of both

specimens are shown in Table 5 and Table 6. As

demonstrated by Table 5, the average hardness of

specimen 1 in the CRA area, HAZ, and base metal

were 208 HV; 196.8 HV; and 195 HV, respectively.

Table 6 shows that specimen 2 had average hardness

in the outer layer 2, inner layer 1, HAZ and base metal

sequentially were 213.8 HV; 219.6 HV; and 203.4

HV for the latter two. It can be calculated that the

average hardness in the CRA area if both specimens

are added is 212.35 HV. Referring to Table 4, the

Vickers hardness number of CRA area in both

specimens followed the acceptance criteria since the

HV obtained was lower than 300 HV. On the other

hand, HAZ and the base metal area was qualified with

hardness numbers not exceeding 248 HV.

According to the measured data, it was recognized

that the material hardness was increased due to the

weld overlay. Comparing the HV at CRA and base

metal, it is known that the hardness of specimen 1 was

improved by 6.67%, while specimen 2 had

increments of 5.11 % at layer 2 and 7.96% at layer 1.

Hence, weld overlay increases the material’s hardness

around 7.32%. This observation might be due to the

carbon diffusion hardens the weld metal through solid

solution strengthening (Akhatova et al., 2020). The

fact that layer 1 was having the highest HV is

expected due to being sandwiched between the base

metal and layer 2, so the area contains more diffusion

then more defects. However, it is required for further

study to confirm the chemical composition in each

layer.

Effect of Stainless Steel Weld Overlay Deposit on the Hardness of API 5L Pipes

121

Table 4: Acceptance criteria for Vickers hardness test (American Petroleum Institute, 2015).

Material Maximum HV allowed

Ferritic steel base metal 248 HV10 at all locations unless otherwise agreed

Austenitic stainless steels 300 HV10 in all locations

22% Duplex stainless steels 300 HV10 in the parent material and 334 HV10 in the weld and HAZ

25% Duplex stainless super

duplex steels

300 HV10 in the parent material and 378 HV10 in the weld and HAZ

Nickel base alloys 345 HV10 in all locations

Table 5: Measured hardness of specimen 1.

Test

Location

Vickers Hardness Number (HV)

Line 1 Line 2 Line 3 Line 4 Line 5 Average

CRA 1 206 221 204 205 204 208

HAZ 2 192 196 202 196 198 196.8

Base

Metal

3 189 188 197 199 193

195

4 202 190 198 199 195

Table 6: Measured hardness of specimen 2.

Test

Location

Vickers Hardness Number (HV)

Line 1 Line 2 Line 3 Line 4 Line 5 Average

CRA

1 203 220 217 219 210 213.8

2 208 219 228 230 213 219.6

HAZ 3 208 210 201 196 202 203.4

Base

Metal

4 207 205 206 204 195 203.4

As seen in Table 6, the hardness of layer 2

relatively lower than layer 1. Apart from the intrinsic

mechanical properties of Novametal 316L that have

the most insufficient tensile strength among materials

used, we expect its position relative to fusion line lead

to carbon diffusion in that area was lower than the

layer 1. Consequently, the outer layer of the clad had

lower hardness than the inner one. The following

Figure 4 and Figure 5 represent the measured HV

numbers of specimen 1 and 2.

Figure 4: Graphical representation of specimen 1 measured

Vickers hardness number (HV).

Those graphs show that the layer 1 consistently

being the hardest part of material. However, it is yet

unclear why the hardness of HAZ and base metal

being alternately fluctuate.

Figure 5: Graphical representation of specimen 2 measured

Vickers hardness number (HV).

4 CONCLUSIONS

In this study, seamless pipes were cladded with two

different filler metals to increase CRA’s corrosion

resistance. The hardness values on the CRA are

higher than those for the untreated metal.

ICAE 2020 - The International Conference on Applied Engineering

122

Nevertheless, the fabricated material could meet the

acceptance criteria in API 5LD standard. However,

further study is required to confirm whether the

stainless steel overlay could improve the material’s

corrosion resistance properties.

ACKNOWLEDGEMENTS

The authors thank PT. Cladtek Bi-Metal

Manufacturing Batam and PT. Hi-Test Laboratory of

Mechanical Testing Batam for their technical

supports.

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