Martensitic (AISI 410) stainless steels are heat treatable type of steel and contain 11.5% to 13% chromium. The combination of strength, toughness, hardness, corrosion resistance, wear resistance and good weldability makes the alloys attractive for the industrial applications such as steam turbine blades, hydraulic turbine blades, valves, bearings, pressure vessels and cutting tools. The metallurgical performance and mechanical performance of the martensitic stainless steels can be modified by heat treatments. The properties of the welded joints are further depends on the various factors like welding process, welding parameters (heat input), filler material, shielding medium, joint design etc. Different post weld heat treatments (annealing, tempering, quenching etc) effect the metallurgical behaviour and mechanical properties of the welded joints
Furthermore, the pre heating temperature and heat treatment parameters (temperature, soaking period and cooling rate) are also affecting the properties of the joints
During the solidification mechanism of martensitic stainless steel the delta ferrite starts to transform into austenite at around 1300 °C and ends at around 1200 °C in thermodynamically equilibrium conditions. At lower temperature the austenite transforms to martensite. During these transformations the small amount of retained ferrite and retained austenite present in the microstructure between the martensite laths
Several experimental studies have conducted and reported on the welding of martensitic stainless steel using various welding processes. However, no such studies on the influence of heat treatments on the pitting and impact toughness behaviour of the AISI 410SS welded joints have been reported. So with the aim of to overcome this research gap, the effect of post weld heat treatments (annealing, quenching and Plasma Nitriding) on the pitting and energy absorption behaviour of the gas tungsten arc welded martensitic stainless steel joint was investigated.
In the present work the martensitic stainless steel (AISI 410SS) was used as a base material (300 mm length, 75mm width and 6mm thick) in the form of rolled plates. The spectroscopy report (chemical composition) of the base plates and filler materials are reported in the
Elements |
C |
Cr |
Ni |
Mn |
S |
Si |
Mo |
P |
Fe |
Base Material (AISI 410 SS) |
0.01 |
11.50 |
0.60 |
1.27 |
0.01 |
0.44 |
0.20 |
0.02 |
Balance |
Filler Material (ER 304LSS) |
0.02 |
18.52 |
9.53 |
1.39 |
0.032 |
1.12 |
-- |
0.04 |
Balance |
Filler Material (ER 410 SS) |
0.12 |
12.51 |
0.55 |
0.61 |
0.035 |
0.51 |
0.60 |
0.03 |
Balance |
Weld Pass number |
Welding Current (ampere) |
Arc Voltage (volt) |
Arc travel Speed (mm/min) |
Heat Input (J/mm.) |
Total Heat Input (kJ/mm) |
Root Pass |
110 |
13 |
0.8333 |
1372.80 |
6.326 |
Cover pass 1 |
125 |
14 |
0.7692 |
1820.00 |
|
Cover pass 2 |
135 |
15 |
0.7018 |
2308.50 |
|
Back cover pass |
130 |
15 |
1.8927 |
824.20 |
The edges of the base plates were thoroughly cleaned before starting the welding operation to avoid any type of contamination like rust, oil, dust particles, moisture etc. the edges of the base plates were pre-heated at 140 to 150 ˚C and inter-pass temperature 240˚C to 250˚C was maintained. The single-v groove design was used and the geometry of the groove design is shown in
S.No. |
Post Weld Heat Treatments |
PT0 |
As received/as welded condition |
PT1 |
Annealing ( 1050 ⁰C for 50 min. followed by slow cooling i.e., furnace cooling) |
PT2 |
Quenching ( 1050 ⁰C for 50 min. followed by water quenching) |
PT3 |
Plasma Nitriding |
In order to determine the pitting behaviour of the weld in as welded condition and different post weld heat treated conditions, a pitting corrosion test was performed on the prepared specimens. As per ASTM G48 standard procedure, the specimens were immersed in the solution of ferric chloride and ionized water for 72 hours
Specimen Condition |
Specimen Name |
Initial mass (mg) |
After pitting test mass (mg) |
Mass loss (mg) |
As Welded |
PT 0 |
24.7691 |
23.519 |
1.2501 |
Annealing ( 1050 ⁰C for 50 min. followed by slow/furnace cooling) |
PT 1 |
21.4224 |
20.7172 |
0.7052 |
Quenching ( 1050 ⁰C for 50 min. followed by water quenching) |
PT 2 |
22.5972 |
22.0281 |
0.5691 |
Plasma Nitriding |
PT 3 |
24.5428 |
24.032 |
0.5108 |
Based on the experimental results charpy V-notch impact test, it was noticed that the maximum toughness in as welded condition/ without any post weld heat treatment of 48 joules. The impact toughness test was performed at room temperature as per the ASTM E23 standard procedure
Specimen Condition |
Specimen Name |
Impact Toughness (CVN) Value in Joules |
As Welded |
PT 0 |
48 |
Annealing ( 1050 ⁰C for 50 min. followed by slow/furnace cooling) |
PT 1 |
62 |
Quenching ( 1050 ⁰C for 50 min. followed by water quenching) |
PT 2 |
26 |
Plasma Nitriding |
PT 3 |
50 |
To evaluate the micro-hardness across the different zones of the weldment, a micro-hardness test was performed on DHV-1000 hardness tester at 4.903 N (500gf) load and 15 sec dwell period. The variation of micro-hardness of the welded joint in as received and different post weld heat treated conditions is shown in
The specimens were machined out from the welded plate and polished up to 2500 grit sized emery papers for microstructural examination of joint. After polishing process, manual etching was done by using etchant of hydrochloric acid (5cc), picric acid (1gram) ethanol (100cc) and few drops of 3% H2O2
On the basis of present experimental work, the following conclusions can be drawn
Pitting resistance of the welded joint is significantly affected by the post weld heat treatments. The maximum pitting resistance is possessed by the plasma nitrided welds.
Post weld heat treatments have the significant effect on the impact toughness behaviour of the joints. Based on the results, the maximum impact toughness (CVN value of 62 joules) was achieved in annealing heat treatment.
Micro-structural studies of the welded joint in as received and post weld heat treated conditions, show that significant microstructural changes were observed in weld metal zones.
The microhardness variations were also observed in the welds. These microhardness variations are due to the microstructural changes.
The authors gratefully acknowledge the research facilities provided by I.K.G. Punjab Technical University, Kapurthala, Punjab, India and Sant Longowal Institute of Engineering and Technology, Longowal (SLIET).