Study of micro structure, mechanical properties & corrosion behavior of weld overlay of super duplex stainless steel on carbon steel substrate by Shielded metal Arc welding

Abstract        

In today’s  industrialization world, there is very common problem faced in every industry from long time where the material wear and tear is happened and required to eliminate as soon as possible to get the more utilization of equipment and avoid the shutdown timing to increase the productivity and earn more and more money for getting good growth in company as well as nation.   The wear and tear mainly occurs due to corrosion, abrasion and erosion. This happens in the chemical process industries, refineries, oil –gas industry, offshore plate forms, steel  mills,  Logistic  industry  etc.  In  these  industries  the  equipment  may  be  statics pressure  equipments,  boilers,  heat  transfer  equipments,  hydro  equipment,  etc.  are working on higher temperatures and getting always the corrosion problems inside the equipment by its processing.  To  achieve  the  good  corrosion  resistance  properties  any of  stainless  steel  category material like austenitic stainless steel, ferritic stainless steel, martensitic stainless steel duplex stainless steel, super duplex stainless steel etc. can be used.  From these all above material super duplex is having very good corrosion resistance properties, higher mechanical strength than the other steel as mentioned, due to rich chemical composition  of  chromium,  Nickel,  molybdenum  and  nitrogen  &  SDSS  is having higher pitting resistance greater than 40 PREN compared to ferritic stainless steel 15 PREN, austenite stainless steel 25 PREN and duplex stainless steel 35 PREN.                   PREN = Wt- %Cr + 3.3 (Wt-%Mo) +16 % (Wt-%N)   

v        To acquires the good corrosion resistance properties in any of the equipment, it can be fabricated for full thickness stainless steel material ,duplex or super duplex stainless steel material but it is not feasible always due to its higher material cost. So regularly it is tried to fabricate from the carbon steel or low alloy steel material as a base metal due to its lower cost with good strength properties with inside lining/cladding/weld overlay of stainless steel material by bonding of different processing methods where the reactive fluid will be come in contact and creates the wear and tear problems due to its corrosive nature. For this bonding process,  different methods  are used based on  the type of material thickness and sizes. Bonding can be done by any of the process like explosive, roll bonding or by weld overlay method.  Weld overlay can be done by different welding process like SMAW, GTAW, SAW, and FCAW  or by ESSC.  Each and  every process  is  having  their own  benefits  and limitations. SMAW is a most commonly used process which is a portable and having lower cost than the other process. This process is very easy to operate even by semi skilled welder. This process is the best due to its approach to work in any position, non accessible areas and at the confined areas averse to other process.       In study work, weld overlay of Super duplex-2594 on SA 516 grade 70 carbon steel using barrier and clad layer of E-2594 welding electrode. Microstructure analysis, bend test,  hardness  test  &  corrosion  testing  were  performed  to  characterization  of  Super duplex-2594 material by SMAW process.    

Table of contents    

 1. Introduction   1-       

 1.1 Cladding/Weld overlay 1        

1.2 Dilution 2        

1.3 Material Used 

2-3 1.3.1 Super Duplex Stainless Steel 3       

 1.4.Characterstic of  Super Duplex Stainless Steel 4 

1.5 Weld Overlay Process for Super Duplex Stainless Steel 5-8             

 1.5.1 Welding Process Used for Weld overlay 5 

1.5.2 Shielded Metal Arc Welding (SMAW) process 6 

1.5.2.1 Principal of process 6

 1.5.2.2 SMAW Polarity 7

 1.5.2.3 SMAW Electrodes 7                     

 1.5.2.4 SMAW Equipment’s  8         

1.5.2.4.1 SMAW Power Source 8         

1.5.2.4.2 SMAW Electrode Holder and Cable 9         

1.5.2.4.3 Cable Lugs 10         

1.5.2.4.4 Hand and head shield  10 

1.5.2.5 Advantages of SMAW 10 

1.5.2.6 Disadvantage of SMAW  11

 1.5.2.7 Applications 11 

2. Literature Review  2.1 Introduction 12-15 

2.2 Literature Survey 16-18 

2.3 Research Gap 18 

2.4    Objectives                                                                                                18   

xi   3.  Experiment and Testing  

3.1  Steps of Experiments          17 

3.2  Base Material and welding electrode 17 

3.3 Welding Machine 18 

3.4 Welding Parameters  19

 3.5 Working Procedure 20 

3.6 Sample Preparation 21

 3.7 Testing of Super Duplex Stainless Steel Weld Overlay 22  

 3.7.1  Non Destructive Examination-NDE  22         

3.7.1.1  Visual Examination 23          

3.7.1.2  Dye Penetrate Testing (DPT) 23                     

 3.7.1.2.1 Principle 23                   

  3.7.1.2.2 Inspection Steps                                               23         

3.7.1.3  Ultrasonic Testing 23  

3.7.2  Bend Testing                                                                                26          

3.7.2.1 Guided Bend Test 26        

 3.7.2.2  Side Bend Test 26  

3.7.3  Macro Examination 28                 

  3.7.3.1 Macro Examination Results 28   

3.7.4  Chemical Analysis of Super Duplex Stainless Steel 28        

 3.7.4.1 Chemical Results of Super Duplex Weld Overlay  28  

3.7.5 Hardness Measurement   30                   

3.7.5.1 Micro Hardness Measurement result 30  

 3.7.6 Micro structural Examination by SEM 30         

3.7.6.1 Introduction                                                                                                                          30  

3.7.7 Chloride stress corrosion cracking test as per ASTM G-36 31      

  3.7.7.1 Introduction                                                                                  35                                     

3.7.8  Corrosion testing as per ASTM G-48 32 

3.7.8.1  Crevice corrosion  32                                                                                                                                       3.7.8.2  Crevice corrosion mechanism 33  

3.8   Result & Discussion 35         

3.8.1   Dye penetrant test & result 35         

3.8.2  Ultrasonic testing 36                   

3.8.2.1  Ultrasonic test result 36        

 3.8.3  Bend test 36                

  3.8.3.1  Side bend test 36                  

3.8.3.2  Side bend test result 37       

 3.8.4  Macro test result 37        

3.8.5  Chemical test result of super duplex 2594 weld overlay                 38        

3.8.6  Hardness measurement result 39        

3.8.7  Micro structural examination result                                                                          40       

 3.8.8  Chloride stress corrosion cracking test 40            

3.8.9  Crevice corrosion test result 41  

4.  Conclusion  42  

 5.  Future Scope 42  

6.  References 43