PSI - Issue 14

A. Poonguzhali et al. / Procedia Structural Integrity 14 (2019) 705–711 Poonguzhali et al. / Structural Integrity Procedia 00 (2018) 000–000 Poonguzhali et al. / Structural Integrity Procedia 00 (2018) 000–000 Poonguzhali et al. / Structural Integrity Procedia 00 (2018) 000–000 Poonguzhali et al. / Structural Integrity Procedia 00 (2018) 000–000 Poonguzhali et al. / Structural Integrity Procedia 00 (2018) 000–000

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composition, inclusions, heat treatment, grain size, sensitisation and secondary precipitates (Sedriks A.J, 1985). Cold deformation is invariably present in components due to fabrication techniques that are known to affect the corrosion resistance due to deformed substructures like dislocation networks, twins and deformation bands. Many of these components are subjected to static, cyclic, thermo-mechanical and flow induced vibrational loads, which induce different kinds of damage like a creep, fatigue, creep-fatigue interaction and high cycle fatigue etc. For the structural integrity assessment, fatigue properties are essential as cyclic loading over the period leading to crack nucleation, growth and final failure. It is known that 90% of fatigue life is consumed for crack initiation and remaining 10% for crack growth under high cycle fatigue condition, which is generated by Wohler/S-N curve to determine the endurance limit. Multiple endurance limits were classified as HCF, VHCF and giga cycle fatigue which are influenced by shot-peening, cold work, strain rate, temperature, surface finish, coatings, residual stress etc. The present study is to evaluate the relationship between differences in the localised corrosion resistance and corrosion fatigue behaviour of AISI type 316 LN SS under a different cold-worked condition in an acidified chloride environment. composition, inclusions, heat treatment, grain size, sensitisation and secondary precipitates (Sedriks A.J, 1985). Cold deformation is invariably present in components due to fabrication techniques that are known to affect the corrosion resistance due to deformed substructures like dislocation networks, twins and deformation bands. Many of these components are subjected to static, cyclic, thermo-mechanical and flow induced vibrational loads, which induce different kinds of damage like a creep, fatigue, creep-fatigue interaction and high cycle fatigue etc. For the structural integrity assessment, fatigue properties are essential as cyclic loading over the period leading to crack nucleation, growth and final failure. It is known that 90% of fatigue life is consumed for crack initiation and remaining 10% for crack growth under high cycle fatigue condition, which is generated by Wohler/S-N curve to determine the endurance limit. Multiple endurance limits were classified as HCF, VHCF and giga cycle fatigue which are influenced by shot-peening, cold work, strain rate, temperature, surface finish, coatings, residual stress etc. The present study is to evaluate the relationship between differences in the localised corrosion resistance and corrosion fatigue behaviour of AISI type 316 LN SS under a different cold-worked condition in an acidified chloride environment. composition, inclusions, heat treatment, grain size, sensitisation and secondary precipitates (Sedriks A.J, 1985). Cold deformatio is invariably present in components due to fabrication techniques that are known to affect the corrosi n resistance due to deformed substructures like dislocation networks, twins and deformation bands. any of these co ponents are subjected to static, cyclic, thermo- echanical and flow induce vibrational loads, which induce different kinds of damage like a creep, fatigue, creep-fatigue interaction and high cycle fatigue tc. For the structural integrity assessment, fatigue properties are essential as cyclic loading over the period leading to crack nucleation, gr wth and final failur . It is known that 90% of fatigue life is consumed for crack initiation and remaining 10% for crack growth under high cycle fatigue condition, which is generated by ohler/S-N curve to deter ine the endurance li it. ultiple endurance li its were classified as HCF, VHCF and giga cycle fatigue which are influenced by sh t-peening, cold work, strain rate, temperature, surface finish, coatings, residual stress etc. The present study is to evaluate the relationship between differences in the localis c rrosi resist nce and corrosion fatigue behaviour of AISI type 316 LN SS under a different cold-worked condition in an acidified chloride environ ent. composition, inclusions, heat treatment, grain size, sensitisation and secondary pr cipitates (Sedriks A.J, 1985). Cold deformation is invariably present in components due to fabrication techniques that are known to affect the corrosion resistance due to deformed substructures like dislocation networks, twins and defor ation bands. Many of these components are subjected to static, cyclic, thermo-mechanical and flow induced vibrational loads, hich induce different kinds of damage like a creep, fatigue, creep-fatigue intera tion nd high cycl fatigue etc. For the structural integrity assessment, fatigue properties are essential as cyclic loading over the period leading to crack nucleation, growth and final failure. It is known that 90% of fatigue life is consu for crack initiation and re aining 10 for cr ck growth under high cycle fatigue condition, which i generated by Wohler/S-N curve to determine the endurance limit. Multiple endurance limits were classified as HCF, VHCF and giga cycle fatigue hich are influenced by sh t-peening, cold work, strain rate, temperature, surface finish, coatings, residual stress etc. The present study is to evaluate the relationship bet een differences in the localis rrosi resist nce and corrosion fatigue behaviour of AISI type 316 LN SS under a different cold-worked condition in an acidified chloride environment. c mposition, inclusions, heat treat ent, grain size, sensitisation and secondary pr cipitates (Sedriks A.J, 1985). C ld deformatio is invariably present in components due to fabrication techniques that are known to affect the corrosion resistance due to deformed subs ruc ures like dislocation networks, twins and deformation bands. M ny of these components are subjected to static, cyclic, ther o- echanical and flow induce v brational loads, which induce different kinds of da age like a creep, fatigue, creep-fatigue interaction nd high cycl fatigue tc. For the structural integrity assess ent, fatigue properties are essential as cyclic loading over the period leading to crack nucleation, growth and final failure. It is known that 90% of fatigue l fe is consum for crack initiation and remaining 10% for c ck growth under high cycle fatigue condition, which is generated by Wohler/S-N curve to determine the endurance li it. ultiple endurance li its were classified as HCF, VHCF and giga cycle fatigue which are influenced by shot-peening, cold work, strain rate, te perature, surface finish, coatings, residual stress etc. The present study is to evaluate the relationship between differences in the localis rros resist nce an corrosion fatigue behaviour of AISI type 316 LN SS under a different cold-worked condition in an acidified chloride environ ent.

Nomenclature σ min Nomenclature σ min No enclature σ in Nomenclature σ in ini Nomenclature σ in minimum stress σ max maximum stress R ratio stress ratio (σ min /σ max ) η frequency σ mean minimum stress σ max maximum stress R ratio stress ratio (σ min /σ max ) η frequency σ mean ini u stress σ max aximu stress R ratio stress ratio (σ min /σ max ) η frequency σ mean stress σ max maximum stress ratio stress ratio (σ min /σ max ) η fr quency σ mean minimum stress σ max maximum stress R ratio stress ratio (σ min /σ max ) η fr quency σ mean pitting potential pitting potential pitting potential pitting potential pitting potential E pit E pit E pit E pit E pit

mean stress (σ min + σ max )/2 mean stress (σ min + σ max )/2 ean stress (σ min + σ max )/2 mean stress (σ min + σ max )/2 mean stress (σ min + σ max )/2

2. Experimental procedure Mill-annealed plates of AISI Type 316 LN SS with 0.11 wt.% nitrogen were cold-rolled at ambient temperature to various levels of reduction in thickness ranging from 5 to 20% and the chemical composition is listed in Table 1. Specimens of size 10 X 10 mm were polished up to lμm finish using diamond paste and electrolytically etched in 10% ammonium persulphate solution at a current density of 1 A/cm 2 for 5 min as per ASTM A262 Practice A test for observing the changes in the microstructure due to cold working. Hardness values of the cold worked specimens were measured using a micro hardness tester of OMNI TECH make (Model –SAUTO) with 500g normal load, 10s loading time on the polished region. An average microhardness value was determined based on five indentation measurements. Potentiodynamic anodic polarization experiments were carried out in acidified deaerated 1 M NaCl and 5M NaCl + 0.15M Na 2 SO 4 solution by purging nitrogen gas through the solution before and during the experiment to avoid oxygen contamination. The potentials were measured against saturated calomel electrode (SCE) and were started from a cathodic potential of -600 mV (SCE) at a scan rate of 0.1 mV/s, till the specimens showed the current value of 0.1 mA due to pitting corrosion attack. Tensile tests were carried out at an initial strain rate of 10 -4 /s both in air to evaluate yield strength (YS), ultimate tensile strength (UTS) and ductility (% total elongation). Corrosion fatigue tests were carried out using round tensile specimen at a (η) of 0.1 Hz using a servo hydraulic system of 25 kN capacity under axial loading in load controlled mode in boiling aqueous solution of 5M NaCl + 0.15M Na 2 SO 4 + 2.5 ml/l HCl (b.p = 381.5 K, pH = 1.3) at different σ mean values and R-ratio of 0.5. Number of cycles to total failure (N f ) was used as the assessment criterion for determining the susceptibility to corrosion fatigue. The CF tested specimens were observed using Mini-SEM (SNE-3000M, M/s. SEC Co, Korea) to investigate the crack morphology. Crack initiation mechanism of CF tested specimen at a mean stress of 375 MPa was studied using atomic force microscopy (AFM). Corrosion products formed on the fractured surfaces after CF tests were characterized using LR spectra with an HR 800 (Jobin Yvon) Raman spectrometer with 1800 grooves/mm holographic grating and a 633 nm He-Ne laser as an excitation source. 2. Experimental procedure Mill-annealed plates of AISI Type 316 LN SS with 0.11 wt.% nitrogen were cold-rolled at ambient temperature to various levels of reduction in thickness ranging from 5 to 20% and the chemical composition is listed in Table 1. Specimens of size 10 X 10 mm were polished up to lμm finish using diamond paste and electrolytically etched in 10% ammonium persulphate solution at a current density of 1 A/cm 2 for 5 min as per ASTM A262 Practice A test for observing the changes in the microstructure due to cold working. Hardness values of the cold worked specimens were measured using a micro hardness tester of OMNI TECH make (Model –SAUTO) with 500g normal load, 10s loading time on the polished region. An average microhardness value was determined based on five indentation measurements. Potentiodynamic anodic polarization experiments were carried out in acidified deaerated 1 M NaCl and 5M NaCl + 0.15M Na 2 SO 4 solution by purging nitrogen gas through the solution before and during the experiment to avoid oxygen contamination. The potentials were measured against saturated calomel electrode (SCE) and were started from a cathodic potential of -600 mV (SCE) at a scan rate of 0.1 mV/s, till the specimens showed the current value of 0.1 mA due to pitting corrosion attack. Tensile tests were carried out at an initial strain rate of 10 -4 /s both in air to evaluate yield strength (YS), ultimate tensile strength (UTS) and ductility (% total elongation). Corrosion fatigue tests were carried out using round tensile specimen at a (η) of 0.1 Hz using a servo hydraulic system of 25 kN capacity under axial loading in load controlled mode in boiling aqueous solution of 5M NaCl + 0.15M Na 2 SO 4 + 2.5 ml/l HCl (b.p = 381.5 K, pH = 1.3) at different σ mean values and R-ratio of 0.5. Number of cycles to total failure (N f ) was used as the assessment criterion for determining the susceptibility to corrosion fatigue. The CF tested specimens were observed using Mini-SEM (SNE-3000M, M/s. SEC Co, Korea) to investigate the crack morphology. Crack initiation mechanism of CF tested specimen at a mean stress of 375 MPa was studied using atomic force microscopy (AFM). Corrosion products formed on the fractured surfaces after CF tests were characterized using LR spectra with an HR 800 (Jobin Yvon) Raman spectrometer with 1800 grooves/mm holographic grating and a 633 nm He-Ne laser as an excitation source. 2. Experi ental procedure ill-anne led plates of AISI Type 316 LN SS with 0.11 wt.% nitrogen were cold-rolled at ambient te perature to various levels of reduction in thickness ranging fro 5 to 20% and the che ical co position is listed in Table 1. Speci ens of size 10 X 10 were polished up to lμm finish using dia ond paste and electrolytically etched in 10% ammonium persulphate solution at a current density of 1 A/cm 2 for 5 min as per ASTM A262 Practice A test for observing the changes in the microstructure due to cold working. H rdness values of the cold worked speci ens were easured using a icro hardness tester of OMNI TECH ake (Model –SAUTO) with 500g normal l ad, 10s loading time on the polished region. An average microh rdness value was determined based on five indentation easure ents. Potentiodyna ic anodic polarization experi ents were carried out in acidified deaerated 1 NaCl and 5 NaCl + 0.15 Na 2 SO 4 solution by purging nitrogen gas through the solution before and during the experiment to avoid oxygen ontamination. The potentials were easured ag inst saturated calomel electrode (SCE) and were started from a cathodic potential of -600 V (SCE) at a scan rate of 0.1 mV/s, till the speci ens showed the current value of 0.1 mA due to pitting corrosion attack. Tensile t sts were carried out at an initial strain rate of 10 -4 /s both in air to evaluate yield strength (YS), ulti ate t il strength (UTS) and ductility ( total elongation). Corrosion fatigue tests were carried out using round tensile specimen at a (η) of 0.1 Hz using a serv hydraulic system of 25 kN capacity under axial loading in load controlled mode in boiling aqueous solution of 5M NaCl + 0.15M Na 2 SO 4 + 2.5 ml/l HCl (b.p = 381.5 K, pH = 1.3) at different σ mean values and R-ratio of 0.5. Nu ber of cycles to total failure (N f ) was used as th assessment criterion for determining the susceptibility to corrosion fatigue. The CF tested speci ens were observed using ini-SE (SNE-3000 , /s. SEC Co, Korea) to investigate the crack morphology. Crack initiation mechanism of CF tested speci en at a ean stress of 375 Pa was studied using atomic force microscopy (AF ). Corrosion pr ducts for ed on the fractured surfaces after CF tests were characterized using LR spectra with an HR 800 (Jobin Yvon) Raman spectrometer with 1800 grooves/mm holographic grating and a 633 nm He-Ne laser as an excitation source. 2. Experimental procedure Mill-annealed plates of ISI Type 316 LN SS with 0.11 t. nitr gen ere cold-rolled at ambient temperature to various levels of reduction in thickness ranging from 5 to 20% and the che ical composition is listed in Table 1. Specimens of size 10 X 10 mm were polished p to lμm finish using diamond paste and electrolytically etched in 10% ammonium persulp te solution at a current density of 1 /c 2 for 5 in as per S 262 Practice A test for observing the changes in the icrostructure due to cold working. Hardness values of the cold worked specimens were measured using a micro hardness test r f OMNI TECH make (Model –SAUT ) ith 500g nor al l ad, 10s loading ti e on the polished region. n average icroh rd ess value was deter ined based on five indentation measurements. Potentiodynamic anodic polarization experiments were carried out in acidified deaerated 1 M NaCl and 5M NaCl + 0.15M Na 2 SO 4 s lution by purging nitrogen gas through the solution before and during the experiment to avoid oxygen contamination. The potentials were measured against saturated calomel electrode (SCE) and w re started from a cathodic potential of -600 mV (SCE) at a scan rate of 0.1 mV/s, till the specimens showed the current value of 0.1 due to pitting corrosion attack. ensile t sts ere carried out at an nitial strain rate of 10 -4 /s both in air to evaluate yield strength (YS), ultimate tensile strength (UTS) and ductility (% total elongation). Corrosion fatigue tests were carried out using round tensile speci en at a (η) of 0.1 Hz using a serv hydraulic system of 25 k capacity under axial loading in load controlled mode in boiling aqueous soluti n of 5M NaCl + 0.15M Na 2 SO 4 + 2.5 ml/l HCl (b.p = 381.5 K, pH = 1.3) at different σ mean values and R-ratio of 0.5. Number of cycles to total failure ( f ) as used as th assess ent criterion for deter ining the susceptibility to c rrosion f igue. The CF tested specimens were observed using Mini-SEM (SNE-3000M, M/s. SEC o, orea) to investigate the crack orphol gy. rack initiation echanis f F tested specime at a mean stre s of 375 MPa was studied using atomic force microscopy (AFM). Corrosion products formed on the fractured surfaces after CF tests were characterized using LR spectra with an HR 800 (Jobin Yvon) a an spectro eter ith 1800 grooves/ holographic grating and a 633 nm He-Ne laser as an excitation source. 2. Experi ental procedure Mill-anne led plat s of AISI Type 316 LN SS with 0.11 wt.% nitr gen were cold-rolled at amb ent temperature to various levels of reduction in thickness ranging fro 5 to 20 and the che ical co position is listed in Table 1. Speci ens of size 10 X 10 were polished up to lμ f nish using diam nd paste and electrolytically etched in 10 a oniu persulphate solution at a current density of 1 A/cm 2 for 5 min as per ASTM A262 Practice A test for observing the changes in the microstructure due to cold working. H rdness values of the cold worked speci ens were measured using a micro hardness test r f OMNI TECH make ( odel –SAUTO) with 500g normal load, 10s loading time on the polished region. An average microhardness value was d termined based on five indentation measurements. Potentiodynamic anodic polarization experi ents were c rried out in acidified deaerated 1 NaCl and 5 NaCl + 0.15 Na 2 SO 4 s lution by purging nitrogen gas through the solution before and during the experi ent to avoid oxygen contamination. The potentials were measured ag inst saturated calo el electrode (SCE) and were started from a cathodic potential of -600 mV (SCE) at a scan rate of 0.1 mV/s, till the specimens showed the current value of 0.1 mA due to pitting corrosion attack. Tensile tests were carried out at an nitial strain rate of 10 -4 /s both in air to evaluate yi ld strength (YS), ulti ate strength (UTS) and ductility ( total elongation). Corrosion fatigue tests were car ied out using round tensile speci en at a (η) of 0.1 Hz using a serv hydraulic syste of 25 kN capacity under axial loading in load controlled ode in boiling aqueous solution of 5M NaCl + 0.15M Na 2 SO 4 + 2.5 l/l HCl (b.p = 381.5 K, pH = 1.3) at different σ mean values and R-ratio of 0.5. Nu ber of cycles to total failure (N f ) was used as the asses ment criterion for determining the susceptibility to c rrosion f igue. The CF tested speci ens were observed using ini-SEM (SNE-3000M, M/s. SEC Co, Korea) to investigate the crack m rphol gy. Crack initiation mechanism of CF tested specime at a mean stress of 375 MPa was studied using ato ic force microscopy (AFM). Corrosion pr ducts formed on the fractured surfaces after CF tests were characterized using LR spectra with an HR 800 (Jobin Yvon) Raman spectrometer with 1800 grooves/mm holographic grating and a 633 nm He-Ne laser as an excitation source.

Table 1. Chemical Composition of 316LN SS (0.11wt. % of nitrogen ). Table 1. Chemical Composition of 316LN SS (0.11wt. % of nitrogen ). Table 1. Chemical Composition of 316LN SS (0.11wt. % of nitrogen ). Table 1. Chemical Composition of 316LN SS (0.11wt. of nitrogen ). Table 1. Chemical Composition of 316LN SS (0.11wt. % of nitrogen ).

Designation Designation Designation Designation Designation 11N 11N 11N 11N 11N

C C C C C 0.03 0.03 0.03 0.03 0.03

Mn Mn Mn Mn Mn 1.78 1.78 1.78 1.78 1.78

Cr Cr Cr Cr Cr 17.62 17.62 17.62 17.62 17.62

Mo Mo Mo Mo Mo 2.51 2.51 2.51 2.51 2.51

Ni Ni Ni Ni Ni 12.27 12.27 12.27 12.27 12.27

Si Si Si Si Si 0.21 0.21 0.21 0.21 0.21

S S S S S

P P P P P

N N N N N 0.11 0.11 0.11 0.11 0.11

Fe Fe Fe Fe Fe Bal Bal Bal Bal Bal

0.005 0.005 0.005 0.005 0.005

0.015 0.015 0.015 0.015 0.015

3. Results and discussions 3. Results and discussions 3. Results and discussions 3. Results and discussions 3. Results and discussions

Fig. 1(a & b) shows the potentiodynamic anodic polarization curves of type 316L SS with 0.11 wt.% nitrogen in acidified two chloride concentrations (1M NaCl) and (5M NaCl + 0.15 M Na 2 SO 4 ) at room temperature. The critical pitting potential (E pit ) and the passivity range drastically decreased with increase in Fig. 1(a & b) shows the potentiodynamic anodic polarization curves of type 316L SS with 0.11 wt.% nitrogen in acidified two chloride concentrations (1M NaCl) and (5M NaCl + 0.15 M Na 2 SO 4 ) at room temperature. The critical pitting potential (E pit ) and the passivity range drastically decreased with increase in Fig. 1(a & b) shows the potentiodyna ic anodic polarization curves of type 316L SS with 0.11 wt. nitrogen in acidified two chloride concentrations (1 NaCl) and (5M NaCl + 0.15 M Na 2 SO 4 ) at room temperature. The critical pitting potential (E pit ) and the passivity range drastically decreased with increase in Fig. 1(a & b) shows the pot nti dynamic anodic pol rization curves of type 3 6L SS with 0.11 wt.% nitrogen in acidified t o chloride concentrations (1M NaCl) and (5 aCl + 0.15 M Na 2 SO 4 ) at room temperature. The critical pitting potential (E pit ) and the passivity range drastically decreased with increase in Fig. 1(a b) shows the pot ntiodynamic anodic polarization curves of type 316L SS with 0.11 wt.% nitrogen in acidified two chloride concentrations (1 NaCl) and (5M NaCl + 0.15 Na 2 SO 4 ) at roo temperature. The critical pitting potential (E pit ) and the passivity range drastically decreased with increase in