scholarly journals Mechanical Properties and Hydrogen Embrittlement of Laser-Surface Melted AISI 430 Ferritic Stainless Steel

Coatings ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 140 ◽  
Author(s):  
W. K. Chan ◽  
C. T. Kwok ◽  
K. H. Lo
Keyword(s):  
Stainless Steel ◽  
Hydrogen Embrittlement ◽  
Strain Rate ◽  
Ferritic Stainless Steel ◽  
Laser Scanning ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Scanning Speed ◽  
Laser Surface ◽  
Aisi 430

In the present study, the feasibility of laser surface melting (LSM) of AISI 430 ferritic stainless steel to minimize hydrogen embrittlement (HE) was investigated. LSM of AISI 430 steel was successfully achieved by a 2.3-kW high power diode laser (HPDL) with scanning speeds of 60 mm/s and 80 mm/s (the samples are designated as V60 and V80, respectively) at a power of 2 kW. To investigate the HE effect on the AISI 430 steel without and with LSM, hydrogen was introduced into specimens by cathodic charging in 0.1 M NaOH solution under galvanostatic conditions at a current density of 30 mA/cm2 and 25 °C. Detail microstructural analysis was performed and the correlation of microstructure with HE was evaluated. By electron backscatter diffraction (EBSD) analysis, the austenite contents for the laser-surface melted specimens V60 and V80 are found to be 0.6 and 1.9 wt%, respectively. The amount of retained austenite in LSM specimens was reduced with lower laser scanning speed. The surface microhardness of the laser-surface melted AISI 430 steel (~280 HV0.2) is found to be increased by 56% as compared with that of the substrate (~180 HV0.2) because of the presence of martensite. The degree of embrittlement caused by hydrogen for the charged and non-charged AISI 430 steel was obtained using slow-strain-rate tensile (SSRT) test in air at a strain rate of 3 × 10−5 s−1. After hydrogen pre-charging, the ductility of as-received AISI 430 steel was reduced from 0.44 to 0.25 while the laser-surface melted AISI 430 steel showed similar tensile properties as the as-received one. After LSM, the value of HE susceptibility Iδ decreases from 43.2% to 38.9% and 38.2% for V60 and V80, respectively, due to the presence of martensite.

The Effect of Sample Preparation on the Microstructure of Austenitic-Ferritic Stainless Steel

2016 ◽  
Vol 879 ◽  
pp. 873-878 ◽  
Author(s):  
Timo Juuti ◽  
Sampo Uusikallio ◽  
Antti J. Kaijalainen ◽  
Esa Heinonen ◽  
Nyo Tun Tun ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Sample Preparation ◽  
Ferritic Stainless Steel ◽  
Laser Scanning ◽  
Focused Ion Beam ◽  
Electron Backscatter Diffraction ◽  
Ion Beam ◽  
Sample Surface ◽  
Laser Scanning Confocal Microscopy ◽  
Mechanical Polishing

Sample preparation of metastable austenitic-ferritic steels can have a significant effect on the apparent microstructure due to the transformation of austenite to martensite (γ - α'). As a result, these steels often have a complex microstructure with ferrite and martensite, which have relatively similar crystal structures, making it very difficult to analyse. However, the quantitative analysis of such microstructures and the effect of the sample preparation are very important for the further study of the steel. In this research, the effect of sample preparation in metastable austenitic-ferritic stainless steel was studied by using three different sample preparation methods. In addition to conventional mechanical etching with colloidical silica and electropolishing, focused ion beam (FIB) milling was used to create an optimal sample surface to be further analysed with electron backscatter diffraction (EBSD). Micrographs were obtained from each sample before and after sample preparation using field emission scanning electron microscopy (FESEM) and laser scanning confocal microscopy (LSCM), and the microstructure was analysed using EBSD. The surface flatness required for good EBSD analysis was significantly better using FIB milling than mechanical polishing, while electropolishing results in the greatest topography and an arched sample surface. The amount of martensite was found to be dependent on the sample preparation: least martensite was formed during electropolishing, while surprisingly mechanical polishing and FIB milling resulted in equal amounts of martensite.

Grains and Sub Grains Identification in AISI 430 Stainless Steel with Atomic and Magnetic Force Microscopies

2005 ◽  
Vol 11 (S03) ◽  
pp. 150-153 ◽  
Author(s):  
J. M. C. Vilela ◽  
N. J. L. de Oliveira ◽  
M. L. Talarico ◽  
M. S. Andrade ◽  
R. A. N. M. Barbosa ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Magnetic Force ◽  
Electron Backscatter Diffraction ◽  
Polarized Light ◽  
Force Microscopy ◽  
430 Stainless Steel ◽  
Anisotropic Plastic ◽  
Backscatter Diffraction ◽  
Aisi 430

Cold rolled sheets of AISI 430 ferritic stainless steel have been widely used in kitchen utensils, ornamental articles, among other products due to their corrosion resistance and good formability. However, a localized increase of the surface roughness, known as ridging, develops during ferritic stainless steel forming [1]. The ridging is caused by anisotropic plastic flow of the material containing alternated bands of different crystallographic textures. These bands, or grain colonies, are formed during hot rolling fabrication step. During this step, the deformed grains can undergo dynamic recrystallization and/or recovery. In the regions where recovery takes place these texture bands are formed. In order to study ridging, it is necessary to identify the recovered regions (regions containing sub grains with nearly the same crystal orientation) and recrystallized regions (regions containing grains with different crystal orientations). Two well established techniques are applied to the characterization of recrystallized and recovered grains: the optical microscopy with polarized light, normally done in samples prepared with colored etching, and the electron backscatter diffraction (EBSD). In this work, atomic force microscopy (AFM) and magnetic force microscopy (MFM) were used to study the recrystallization and the recovery of the deformed specimens.

Recrystallization of Coarse-Grained Nb-Containing AISI-430 Ferritic Stainless Steel

2010 ◽  
Vol 638-642 ◽  
pp. 3009-3014 ◽  
Author(s):  
Rodrigo P. Siqueira ◽  
Hugo Ricardo Zschommler Sandim ◽  
Tarcisio R. Oliveira
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Electron Backscatter Diffraction ◽  
Secondary Recrystallization ◽  
Coarse Grained ◽  
Ferritic Stainless Steels ◽  
Coarse Grains ◽  
Cold Rolled ◽  
Backscatter Diffraction ◽  
Aisi 430

Ferritic stainless steels (FSSs) have excellent corrosion resistance and good mechanical properties. Applications include heaters, houseware, and automotive exhaust systems. Alloying, even in small amounts, affects the recrystallization behavior of FSSs by selective dragging or pinning effects. In the present study, we present the main results regarding the recrystallization of a coarse-grained Nb-containing AISI 430 ferritic stainless steel. The material was processed by hot rolling and further annealed at 1250oC for 2 h to promote secondary recrystallization. Following, the material was cold rolled to a 80% reduction in thickness and annealed at 400-1000oC for 15 min. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to characterize the microstructure. Recrystallization of this steel begins at 700oC. Important orientation effects were observed in both as-rolled and annealed conditions. Recrystallization kinetics was strongly dependent on the initial orientation of the coarse grains. Results show that grain boundaries, transition bands and coarse Nb(C,N) particles are preferential sites for nucleation at moderate annealing temperatures.

Continuous drive friction welding studies on AISI 430 ferritic stainless steel

2003 ◽  
Vol 8 (3) ◽  
pp. 184-193 ◽  
Author(s):  
V. V. Satyanarayana ◽  
G. Madhusudhan Reddy ◽  
T. Mohandas ◽  
G. Venkata Rao
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Friction Welding ◽  
Aisi 430

scholarly journals Effect of Hot Isostatic Pressing on Porosity and Mechanical Properties of 316 L Stainless Steel Prepared by the Selective Laser Melting Method

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4377
Author(s):  
Tomas Cegan ◽  
Marek Pagac ◽  
Jan Jurica ◽  
Katerina Skotnicova ◽  
Jiri Hajnys ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Hot Isostatic Pressing ◽  
Microstructural Analysis ◽  
Scanning Speed ◽  
High Yield ◽  
Laser Method ◽  
Preparation Conditions ◽  
Lower Porosity ◽  
316 L Stainless Steel

The manufacturing route primarily determines the properties of materials prepared by additive manufacturing methods. In this work, the microstructural features and mechanical properties of 316 L stainless steel prepared by the selective laser method have been determined. Three types of samples, (i) selective laser melted (SLM), (ii) selective laser melted and hot isostatic pressed (HIP) and (iii) selective laser melted and heat treated (HT), were characterized. Microstructural analysis revealed that SLM samples were formed by melt pool boundaries with fine cellular–dendritic-type microstructure. This type of microstructure disappeared after HT or HIP and material were formed by larger grains and sharply defined grain boundaries. The SLM-prepared samples contained different levels of porosity depending on the preparation conditions. The open interconnected LOF (lack of fusion) pores were observed in the samples, which were prepared with using of scanning speed 1200 mm/s. The blowhole and keyhole type of porosity were observed in the samples prepared by lower scanning speeds. The HIP caused a significant decrease in internal closed porosity to 0.1%, and a higher pressure of 190 MPa was more effective than the usually used pressure of 140 MPa, but for samples with open porosity, HIP was not effective. The relatively high yield strength of 570 MPa, tensile strength of 650 MPa and low ductility of 30–34% were determined for SLM samples with the lower porosity content than 1.3%. The samples after HIP showed lower yield strengths than after SLM (from 290 to 325 MPa) and relatively high ductility of 47.8–48.5%, regardless of the used SLM conditions.

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