Huey Test Research Articles

Additive manufacturing of duplex stainless steel by DED-LB/M and PBF-LB/M – process-material-property relationships

PurposeAdditive manufacturing (AM) of duplex stainless steels (DSS) is still challenging in terms of simultaneously generating structures with high build quality and adequate functional properties. This study aims to investigate comprehensive process-material-property relationships resulting from both laser-directed energy deposition (DED-LB/M) and laser powder bed fusion (PBF-LB/M) of DSS 1.4462 in as-built (AB) and subsequent heat-treated (HT) states.Design/methodology/approachCuboid specimens made of DSS 1.4462 were generated using both AM processes. Porosity and microstructure analyses, magnetic-inductive ferrite and Vickers hardness measurements, tensile and Charpy impacts tests, fracture analysis, critical pitting corrosion temperature measurements and Huey tests were performed on specimens in the AB and HT states.FindingsCorrelations between the microstructural aspects and the resulting functional properties (mechanical properties and corrosion resistance) were demonstrated and compared. The mechanical properties of DED-LB/M specimens in both material conditions fulfilled the alloy specifications of 1.4462. Owing to the low ductility and toughness of PBF-LB/M specimens in the AB state, a post-process heat treatment was required to exceed the minimum alloy specification limits. Furthermore, the homogenization heat treatment significantly improved the corrosion resistance of DED- and PBF-processed 1.4462.Originality/valueThis study fulfills the need to investigate the complex relationships between process characteristics and the resulting material properties of additively manufactured DSS.

The Effect of Severe Plastic Deformation on the Corrosion Resistance of AISI Type 304L Stainless Steel

The AISI type 304L stainless steel (SS) was solution annealed at 1050 °C and cryo-rolled at liquid nitrogen (L-N2) temperature (77 K) under severe plastic deformation (SPD). The thickness reduction through cryo-rolling plastic deformation was carried out up to 90% (designated as CR-90) of initial thickness. The cryo-rolling during rolling at liquid N2 temperature (77 K), resulted in transformation induced plastic deformation of the austenite γ-phase into α’- martensite phase. The phase transformation was characterized by x-ray diffraction (XRD) and saturation magnetization (Ms) measurement. The microstructure was measured by using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD peak positions confirmed the martensite (α’) phase formation. Saturation magnetization (Ms) value of the cryo-rolled specimens shows increasing linearity with cryo-rolling, and transformed to bct martensite (α’). The measured corrosion rate of the cryo-rolled specimens as per ASTM A-262 practice-C test (Huey test) ranges from 6.6 mpy or 0.167 mm/yr (CR 0) to 12.9 mpy or 0.328 mm/yr (CR 90), indicating the effects of severe deformation of strain-induced martensite with the cryo-rolling. Further, the role of severe deformation of strain-induced martensite with the cryo-rolling on AISI type 304L SS and also influence on the corrosion resistance are investigated in detail. The deformation microstructure roles, i.e., the phases and volume percentage induced by the different percentage of the cryo-rolling that influences the corrosion resistance properties and corresponding corrosion resistance in nitric acid have been investigated.

Effect of heat treatment on the microstructure and corrosion resistance behavior of ENiCrFe-7 weld overlay cladding material

The effect of heat treatment on the microstructure and corrosion resistance behavior of alloy ENiCrFe-7 had been investigated. The results showed there were more and bigger transgranular niobium carbide with increasing heat treatment time, the effect of heat treatment on (Al–Ti–O)-rich transgranular precipitates was not obvious. Heat treatment promoted formation of the intergranular precipitates. Huey test showed there were more and more severe intergranular corrosion, which resulted from intergranular precipitates, and more serious interdendritic corrosion were induced by niobium carbide precipitated with increasing heat treatment time. (Al–Ti–O)-rich phase was Al2O3 and niobium carbide phase was NbC, the intergranular precipitates consisted of Nb5Si3 and a small amount of Cr23C6, Cr3C2 and Cr7C3 phase. The corrosion product was a mixture of SiO2 amorphous and oxynitride, the microvoid was formed in corrosion product.

Effect of The Degree of Cold Work and Sensitization Time on Intergranular Corrosion Behavior in Austenitic Stainless Steel

Abstract Present paper deals with the influence of a wide range of cold rolling (5, 10, 15 and maximum 40% cold deformation) and the sensitization time (aging at 700°C for 0.12, 0.5, 1, 4, 16 and 32 hours) on intergranular corrosion (IGC). Intergranular corrosion of commercial stainless steel type X6CrNiTi18-10 (1.4541, AISI 321) is frequently observed in several process environments. These localized attacks are normally attributed to the carbide precipitation and concomitant depletion of chromium near grain boundary due to steel exposure to sensitization temperature. Such undesirable microchemistry is expected to be changed further if the material undergoes deformation prior to sensitization. The consequences of deformation on IGC have been investigated by using EN ISO 3651-1methods (Huey test – Corrosion test in nitric acid medium by measurement of loss in mass). Introducing deformation to the investigated stainless steel seems to change the kinetics of carbide precipitation M23C6 and thereby changes it resistance to IGC. Cold deformation before sensitization reduces the intensity of intergranular corrosion of this steel. The deformed structure created during the cold work process, numerous slip planes and the twins boundaries are just like the grain boundaries and the places where the chromium carbides preferentially precipitates. Due to the more evenly occurring precipitation processes within the whole deformed grains, there is no phenomenon of local grain boundary carbide precipitation, and thus there is no decrease in the resistance of this steel to intergranular corrosion. The assessment of the degree of intergranular corrosion was based on the measurement of mass loss and observation of corroded surfaces on optical and electron transmission and scanning microscopes.

Influence of filler material composition on the microstructural evolution, mechanical properties and corrosion behaviour of nickel-based super alloy C-276

The microstructural evolution, mechanical properties and corrosion resistance of nickel-based-Super Alloy C-276 joints were examined in the current investigation. Four different filler materials (ERNiCrMo-4, ERNiCrMo-10, ERNiCrMo-3 and ERNiCr-3) in combination with pulsed current gas tungsten arc welding were used to join 6 mm thick sheets of Alloy C-276. The better understanding of evolution of microstructures and their subsequent effect on the properties would be beneficial for employing such joints in practical applications. The microstructural analysis showed transition in the solidified structure for different filler materials. Furthermore, SEM-EDS analysis clearly revealed the precipitation of Mo or Nb-rich precipitates in the welds (or close to fusion boundary) for all the weldments. This situation caused a reduction in the mechanical properties and the initiation of corrosion pits (or cracking) during modified Huey test. However, the segregation of TCP phases (P or μ) was found to be in a lesser amount in the ERNiCrMo-4 weld followed by ERNiCrMo-10 weld (which needs further investigation) and hence resulted in a better mechanical properties and superior corrosion resistance as compared to the weld fabricated using ERNiCr-3 filler material. Therefore, the authors recommend the use of ERNiCrMo-4 filler material for joining of Alloy C-276 (followed by ERNiCrMo-10 filler material) in corrosive industrial applications.

Consumable selection for pulsed current gas tungsten arc welded bimetallic joints between Super C-276 alloy and Ti -stabilized Grade 321

The present work investigates the influence of filler materials composition on the bimetallic joints between nickel based Super C-276 alloy and Ti-stabilized Grade 321 using multi-pass pulsed current gas tungsten arc welding process. The analysis was carried out to determine the correlationship between the morphology of the weld metals and the resultant mechanical properties and corrosion resistance. Four different filler materials including ERNiCrMo-4, ERNiCrMo-3, ERNiCr-3 and ER347 were employed. The microstructural analysis revealed fully austenitic structure along with variation in the dendritic morphology from cellular/columnar to an equiaxed structure near weld center line for different filler materials. SEM-EDS point analysis results displayed the existence of white particles (both Mo and Nb-rich) in the weld as well as at the weld boundaries occupying the interdendritic regions on account of their low solubility in the matrix. Compositional analysis revealed that the ERNiCr-3 weld had greater degree of Nb-rich precipitation occurred along the migrated grain boundaries which causes cracking in the weld during modified Huey test. Mechanical test results indicates that amongst all dissimilar weldments, welds fabricated by employing ERNiCrMo-4 and ERNiCrMo-3 showed the optimum properties. In conclusion, for the dissimilar joining of Super C-276 alloy and Ti stabilized Grade 321, ERNiCrMo-4 filler material (followed by ERNiCrMo-3) offers superior properties compared to other filler materials employed.

Diagnostics of the effect of prior cold deformation and aging time on intergranular corrosion resistance in case of austenitic stainless steel

Intergranular corrosion of commercial stainless steel type X6CrNiTi18-10 (1.4541, AISI 321) is frequently observed in several process environments. These localized attacks are normally attributed to the carbide precipitation and concomitant depletion of chromium near grain boundary due to steel exposure to sensitization temperature. Such undesirable microchemistry is expected to be changed further if the material undergoes deformation prior to sensitization. Present paper deals with the influence of a wide range of cold rolling (5, 10, 15 and maximum 40% cold deformation) and the sensitization time (aging at 700°C for 0.12, 0.5, 1, 4, 16 and 32 hours) on intergranular corrosion (IGC). The assessment of the degree of intergranular corrosion was based on the measurement of mass loss and observation of corroded surfaces on optical microscope. The consequences of deformation on IGC have been investigated by using EN ISO 3651-1methods (Huey test). Cold deformation before sensitization reduces the intensity of intergranular corrosion of this steel. The deformed structure created during the cold work process, numerous slip planes and the twins boundaries are just like the grain boundaries and the places where the chromium carbides preferentially precipitates.

Optimization of the Double Loop Electrochemical Potentiokinetic Reactivation Method for Detecting Sensitization of Nickel Alloy 690

Nickel alloy 690 (UNS N06690) is one of the current choices for nuclear power plant steam generator tubing. The severity of certain stress corrosion cracking submodes in Ni-Cr-Fe alloys, such as Alloy 690, may be a function of the alloy sensitization condition. Sensitization results from chromium carbide precipitation at or near grain boundaries when the alloy is exposed to temperatures from 500°C to 800°C, which causes local chromium depletion in the adjacent matrix. The objective of this work was to study the parameters that control the double loop electrochemical potentiokinetic reactivation (DL-EPR) method and to develop an optimized test routine for Alloy 690. Alloy 690 specimens were tested under different thermal treatments, tailored to obtain a variety of concentrations of chromium in solid solution near the grain boundary (GB) region. The DL-EPR method was applied to Alloy 690 in solutions with different concentrations of sulfuric acid and potassium thiocyanate, at 30°C and 50°C. The optimal condition for detecting sensitization of Alloy 690 was 0.5 M H2SO4 + 0.001 M KSCN, at 30°C. Optical micrographs confirmed an intergranular type of attack under thermally aged (sensitized) conditions. The ratio of the reactivation to the activation peak intensities (Ir/Ia) obtained in the DL-EPR test agreed well with mass loss obtained in boiling nitric acid solution with Cr(VI) additions (modified Huey test). Chromium depletion profiles near the GB of thermally treated specimens under different conditions were measured with the energy dispersive x-ray spectroscopy technique, performed on a transmission electron microscope. A model available in the literature was fitted to those results. The Ir/Ia ratio for Alloy 690, obtained when using the optimal DL-EPR testing conditions, correlated well with the Cr depletion zone width and depth near the GB.

Effect of cooling condition on the intergranular corrosion resistance of UNS S32506 duplex stainless steel

The effect of cooling condition on the intergranular corrosion resistance of UNS S32506 duplex stainless steel was investigated by means of Huey test and microstructural observation. It was found that quenching at a temperature below 800°C after air cooling at a fixed rate from solutionization temperature enhances the intergranular corrosion rate. No precipitation has been found at all cooling conditions. Formation of Cr-depletion zone on the γ phase side of the α/γ interface due to local chemical change accompanying α-γ phase transformation during air cooling is responsible for the intergranular corrosion degradation of the UNS S32506 duplex stainless steel.

Effect of Nb on the Corrosion Resistance of Ni-Cr-Fe-Based Weld Metals

The localized corrosion behaviors (intergranular corrosion, pitting, and interdendritic corrosion) of Ni-Cr-Fe-based weld metals with different niobium concentrations were investigated both in the as-welded and heat-treated conditions using the modified Huey test (ASTM A262-2010). Results indicated that Nb could reduce the intergranular corrosion susceptibility of Ni-Cr-Fe-based weld metals by preventing Cr carbides from precipitating at grain boundaries. However, the degree of pitting corrosion became more severe with the increase of Nb. The Laves phase could be corroded easily in the oxidizing environment, which increased the pitting corrosion sensitivity of weld metals. Interdendritic corrosion became the main corrosion type of weld metals that were heat treated at 620°C for 29 h. The depletions of elements Cr and Ni occurred in the interdendritic region, which resulted in the interdendritic corrosion of the heat-treated weld metals. With increasing Nb, the degree of Cr and Ni depletions became higher ...

원자력발전소용 316 스테인리스강 배관의 부식특성에 미치는 유도가열벤딩공정의 영향

Recently, the application of bending products has been increased since the industries such as automobile, aerospace, ships, and plants greatly need the usage of pipes. For facility fabrication, bending process is one of key technologies for pipings. Induction heat bending process is composed of bending deformation by repeated local heat and cooling. Because of local heating and compressive strain, detrimental phases may be precipitated and microstructural change can be induced. This work focused on the effect of induction heat bending process on the properties of ASME SA312 TP316 stainless steel. Evaluation was done on the base metal and the bended areas before and after heat treatment. Microstructure analysis, intergranular corrosion test including Huey test, double loop electropotentiokinetic reactivation test, oxalic acid etch test, and anodic polarization test were performed. On the base of microstructural analysis, grain boundaries in bended extrados area were zagged by bending process, but there were no precipitates in grain and grain boundary and the intergranular corrosion rate was similar to that of base metal. However, pitting potentials of bended area were lower than that of the base metal and zagged boundaries was one of the pitting initiation sites. By re-annealing treatment, grain boundary was recovered and pitting potential was similar to that of the base metal.

Effects of Cr - Ni 18/9 Austenitic Cast Steel Modification by Mischmetal

Abstract This paper presents the results of Cr - Ni 18/9 austenitic cast steel modifications by mischmetal. The study was conducted on industrial melts. Cast steel was melted in an electric induction furnace with a capacity of 2000 kg and a basic lining crucible. .The mischmetal was introduced into the ladle during tapping of the cast steel from the furnace. The effectiveness of modification was examined with the carbon content of 0.1% and the presence of δ ferrite in the structure of cast steel stabilized with titanium. The changes in the structure of cast steel and their effect on mechanical properties and intergranular corrosion were studied. It was found that rare earth metals decrease the sulfur content in cast steel and above all, they cause a distinct change in morphology of the δ ferrite and non-metallic inclusions. These changes have improved mechanical properties. R02, Rm, and A5 and toughness increased significantly. There was a great increase of the resistance to intergranular corrosion in the Huey test. The study confirmed the high efficiency of cast steel modification by mischmetal in industrial environments. The final effect of modification depends on the form and manner of placing mischmetal into the liquid metal and the melting technology, ie the degree of deoxidation and desulfurization of the metal in the furnace.

UNS N08810 합금의 입계부식손상과 원인 분석

Corrosion failure of petrochemical facilities is one of the difficulties in maintenance, since operating conditions of crude oil production, storage, and refinement are very aggressive. UNS N08810, which has been used for crude oil transportation pipes and storage tanks in petrochemical industries, shows good resistance to general corrosion and localized corrosion in several environments. Among its environments, UNS N08810 showed better corrosion resistance in fuel gas containing sulfuric acid and phosphoric acid and sulfur. However, ductility and toughness at high temperature over about <TEX>$500^{\circ}C$</TEX> were greatly reduced due to microstructural change. In general, welding process is the representative method to join the parts in industrial components. Because the alloy by welding can be sensitized and corroded, the manufacturing process should be controlled. In this work, UNS N08810 was used and heat treatment conditions including solution and stabilization treatments were controlled. Oxalic acid etch test by ASTM A262 Practice A was done to evaluate the qualitative sensitization in room temperature. Huey test by ASTM A262 Practice C was done to evaluate the intergranular corrosion rate in boiling 65% <TEX>$HNO_3$</TEX> solution. Also, the microstructure by thermal history was analyzed. Experimental alloy showed high intergranular corrosion rate and its corrosion mechanism was elucidated.

Effects of beam offset on mechanical properties and corrosion resistance of Alloy 690–SUS 304L EBW joints for nuclear power plant

The current study investigates the effect of the beam offset (BOF) on the microstructure, mechanical properties, and the corrosion resistance of the fusion zone (FZ) of Alloy 690–SUS 304L stainless steel (SS) dissimilar metal butt joints formed by electron beam welding (EBW). The experimental results showed that as the value of the BOF increased from 0 to 0.30 mm, i.e. the electron beam shifted progressively toward the Alloy 690 base metal (BM), the tensile strength of the FZ fell from 582.1 to 541.2 MPa. However, the modified Huey test results indicated that the interdendritic corrosion resistance of the FZ was significantly enhanced. Pit nucleation potential value ( E np) was raised from 385 to 1050 mV. An offset of 0.30 mm appears to be the optimal BOF setting when fabricating Alloy 690–SUS 304L SS dissimilar metal butt joints using the EBW technique.

Pitting of 316L stainless steel in flare piping of a petrochemical plant

Pitting was observed on a 6-in. (15 cm) flare piping made of stainless steel ASTM A312 Gr. Tp 316L, prior going into service in a petrochemical plant. The pits were in the heat-affected zone (HAZ) and fusion zone (FZ) boundary of the pipe seam welds. The FZ was also uniformly corroded. The SEM photomicrographs showed large inclusions in the welded area, while EDS analysis indicated that the inclusions were rich in Al, Si, and S. The Streicher test indicated no sensitization in the welded area. The Huey test confirmed that the corrosion rate of samples from welded area were higher that of samples from base metal in a boiling nitric acid test.

Silicon Influence on Corrosion Properties of Austenitic Stainless Steels

In the present paper there are presented results concerning comparative corrosion resistance of some austenitic stainless steels, with or without silicon content. The silicon content is varying in the range of 1-5 %, in a matrix of alloyed austenite, containing 20% Cr and 15-18%Ni and with very low carbon contents (lower than 0,03% C). There are investigated different types of corrosion resistance: intergranular corrosion in nitrogen media, stress corrosion resistance in chloride media, and transpassive behaviour in sulphuric media. The testing media contained nitrogen, as it follows: Huey test (65% HNO3, at boiling temperature, 244 hours maintain), and 5N HNO3 +1g/l Cr6+ (144 h, at boiling temperature). The media containing chloride is 45% MgCl2 at boiling temperature, with a period of 1000 hours. The transpassive behaviour is tested in 10% HSO4. The investigations were made by optic and electronic microscope, and the corroded surfaces were examined by scanning electron microscopy.

Precipitated Phases and Corrosion Behavior in the Dissimilar Alloy 690-SUS 304L Joints Formed by EBW and GTAW

This study investigates the correlation between the microstructure and the corrosion resistance properties of the fusion zone of Alloy 690-SUS 304L stainless steel dissimilar weldments formed by electron beam welding (EBW). The effects of the EBW process are evaluated by comparing the microstructure and corrosion resistance properties of the EBW weldment with those of Alloy 690-SUS 304L weldment formed by gas tungsten arc welding (GTAW). The experimental results reveal that the interdendritic region of the fusion zone of the EBW weldment contains fine TiN precipitates and Cr-Ni rich phases. The TiN precipitates are originated from the Alloy 690 base metal, while the Cr-Ni rich phases, a new formation of precipitates, is precipitated in the region around TiN during solidification. Microscopic analysis of the samples following a modified Huey test indicates that the matrix around TiN precipitate and the Cr-Ni rich phase precipitate provide the preferred sites for corrosion pit initiation. Due to the rapid cooling in the EBW process, relatively fewer and smaller TiN precipitates and Cr-Ni rich phases are formed in the weldment. Consequently, only limited corrosive pitting is observed which indicates better interdendritic corrosion resistance properties in comparison to joints with GTAW process. Furthermore, rapid solidification in the fusion zone results not only the suppression of chromium carbide precipitation but also the chromium depletion at the grain boundaries. As a result, the intergranular corrosion resistance and interdendritic corrosion resistance of the EBW weldment are significantly higher than that of the GTAW weldment.

Development of EPR Test Technique for Alloy 800

The degree of sensitization (DOS) of austenitic stainless steels and some nickel-based alloys (e.g., alloy 600) is evaluated by the electrochemical potentiokinetic reactivation (EPR) test. In this study a number of test solutions based on H2SO4 + KSCN composition have been evaluated to establish a reliable EPR test method for alloy 800. Different passivation (vertex) potentials are also tested. It has been shown that dilute test solutions with lower vertex potentials resulted in single loop (SL) and double loop (DL) EPR test methods that distinguished between different sensitized samples and also between sensitized and desensitized samples. It has been shown that an SL-EPR test in 1 M H2SO4 + 0.002 M KSCN (de-aerated) at 26 °C at a scan rate of 3 mV/s from a vertex potential of 700 mVSCE (180 s hold time) gave results that matched with the DOS indicated by microstructures and the Huey test results. Similarly, the DL-EPR test in 1 M H2SO4 + 0.002 M KSCN (de-aerated) at 26 °C, forward scanning from the OCP to + 700 mVSCE and then backward scanning from there to the OCP at a scan rate of 2 mV/s produced a good measure of DOS as indicated by the Huey test results. The effectiveness of the EPR test was ascertained by testing on alloy 800 containing Ti and Al (alloy 800 HT) and Nb (alloy 800 Nb).

Role Of M23C6 Carbide Precipitation and Phosphorus Grain Boundary Segregation in Intergranular Fracture and Corrosion of 18Cr-12Ni Austenitic Stainless Steel

The effects of intergranular precipitation (size of precipitates) and phosphorus grain boundary segregation on fracture and corrosion behaviours of the 18Cr-12Ni steel were investigated. In the investigation, techniques of light microscopy, SEM, TEM, AES, EDX, electron diffraction, and the Huey test were used. A good correlation was found between the average size of intergranular particles and the portion of intergranular fracture for samples impact loaded at 173 K. The equilibrium values of phosphorus grain boundary concentration showed the close correlation with the values of weight loss (penetration depth) measured during the Huey test.

Corrosion resistance of sintered austenitic stainless steels in boiling nitric acid

A comparative study of the corrosion resistance in boiling nitric acid has been carried out for P/M and cast AISI 304L and AISI 316L stainless steels. The influence of sensitization and acid concentration on the corrosion rate have been determined. The results are discussed with reference to ASTM A262 (Huey test). Scanning electron microscopy was used to study the microstructural characteristics and the corrosion products. It is shown that the corrosion phenomenon in P/M steels is almost entirely due to pore induced crevices; a possible corrosion mechanism for the materials is proposed.