Moderate Corrosion Resistance Research Articles

Effect of shot peening and treatment temperature on wear and corrosion resistance of sequentially plasma treated AISI 316L steel

Austenitic stainless steels exhibit excellent corrosion resistance but relatively poor wear resistance. Previous investigations have demonstrated that surface treatments consisting of plasma carburizing and plasma nitriding were able to successfully increase the wear resistance of austenitic stainless steels. In this work, the effect of a prior shot peening (SP) process on wear and corrosion resistance of sequentially plasma carburized and plasma nitrided AISI 316L austenitic stainless steel was investigated. Triode plasma carburizing (TPC) and triode plasma nitriding (TPN) were sequentially carried out at two temperatures: 400°C and 475°C. SP processing prior to sequential plasma treatments led to a significant increase in the near-surface hardness. The sequential plasma treatment at 475°C in combination with a SP pre-treatment promoted a further increase in thicknesses of carburized and nitrided layers, leading to a greater hardening depth. The best wear resistance exhibited by austenitic AISI 316L samples subjected to SP and sequential plasma processing at higher temperature could be attributed to their high surface hardness and greater treatment depth. However, this treatment at higher temperature yielded CrN precipitates that impaired the corrosion resistance in aerated 0.5M H2SO4 aqueous solution. Electrochemical tests also revealed that the use of shoot peening prior to sequential plasma treatments at 475°C could partially counteract the deleterious reduction in corrosion resistance promoted by chromium nitride precipitation at this higher processing temperature. Although the precipitation of chromium nitrides at higher plasma processing temperatures promoted a reduction in corrosion resistance in such acidic environment, results indicate that austenitic stainless steels modified by shot peening (SP) followed by sequential plasma treatments at high processing temperatures could be potentially used in applications where high wear resistance and moderate corrosion resistance in specific environments are required.

Microstructural Evolution and Mechanical Properties of Simulated Heat-Affected Zones in Cast Precipitation-Hardened Stainless Steels 17-4 and 13-8+Mo

Cast precipitation-hardened (PH) stainless steels 17-4 and 13-8+Mo are used in applications that require a combination of high strength and moderate corrosion resistance. Many such applications require fabrication and/or casting repair by fusion welding. The purpose of this work is to develop an understanding of microstructural evolution and resultant mechanical properties of these materials when subjected to weld thermal cycles. Samples of each material were subjected to heat-affected zone (HAZ) thermal cycles in the solution-treated and aged condition (S-A-W condition) and solution-treated condition with a postweld thermal cycle age (S-W-A condition). Dilatometry was used to establish the onset of various phase transformation temperatures. Light optical microscopy (LOM), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS) were used to characterize the microstructures, and comparisons were made to gas metal arc welds that were heat treated in the same conditions. Tensile testing was also performed. MatCalc thermodynamic and kinetic modeling software was used to predict the evolution of copper (Cu)-rich body center cubic precipitates in 17-4 and β-NiAl precipitates in 13-8+Mo. The yield strength was lower in the simulated HAZ samples of both materials prepared in the S-A-W condition when compared to their respective base metals. Samples prepared in the S-W-A condition had higher and more uniform yield strengths for both materials. Significant changes were observed in the matrix microstructure of various HAZ regions depending on the peak temperature, and these microstructural changes were interpreted with the aid of dilatometry results, LOM, SEM, and EDS. Despite these significant changes to the matrix microstructure, the changes in mechanical properties appear to be governed primarily by the precipitation behavior. The decrease in strength in the HAZ samples prepared in the S-A-W condition was attributed to the dissolution of precipitates, which was supported by the MatCalc modeling results. MatCalc modeling results for samples in the S-W-A condition predicted uniform size of precipitates across all regions of the HAZ, and these predictions were supported by the observed trends in mechanical properties. Cross-weld tensile tests performed on GMA welds showed the same trends in mechanical behavior as the simulated HAZ samples. Welding in the S-W-A condition resulted in over 90 pct retention in yield strength when compared to base metal strengths. These findings indicate that welding these PH stainless steels in the solution-treated condition and using a postweld age will provide better and more uniform mechanical properties in the HAZ that are more consistent with the base metal properties.

Effect of Heat Treatment on the Microstructure and Mechanical Properties of a Welded AISI 410 Martensitic Stainless Steel

2 Abstract: Although martensitic stainless steel materials are not used in large quantities compared to austenitic and ferritic grades, they play a huge and often unseen part in our modern world due to their combination of strength, toughness and moderate corrosion resistance. However, after welding the martensitic stainless steel tend to lose their mechanical/microstructural integrity. In this study, the microstructures and mechanical properties of a welded AISI 410 martensitic stainless steel after different heat treatments were studied, with aims to restore the hardness and improve grain refinement of the materials. The results show that the structures of the steel after austenitizing treatment at 1020°C are of lath martensite mixed with a small amount of retained austenite. Apart from TP2 specimen, where martensite phase was transformed into ferrite structure, the structures of the tempered steel are mixtures of tempered martensite, carbides and reversed austenite dispersed in the martensite matrix. The result indicated that the tempering regimens (500, 600 and 700°C) carried out improved the hardness and grain refinement leading to the existence of finely distributed carbides in the materials. TheTP3 specimen experienced secondary hardening phenomenon, displays the best comprehensive mechanical properties and has the highest hardness value of 370.7 HV close to the parent metal after tempering at 700 °C.

Advanced characterization study of commercial conversion and electrocoating structures on magnesium alloys AZ31B and ZE10A

The local metal-coating interface microstructure and chemistry formed on commercial magnesium alloys Mg–3Al–1Zn (AZ31B) and Mg–1Zn–0.25Zr–<0.5Nd (ZE10A, ZEK100 type) were analyzed as-chemical conversion coated with a commercial hexafluoro-titanate/zirconate type + organic polymer based treatment (Bonderite® 5200) and a commercial hexafluoro-zirconate type + trivalent chromium Cr3 + type treatment (Surtec® 650), and after the same conversion coatings followed by electrocoating with an epoxy based coating, Cathoguard® 525. Characterization techniques included scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and cross-section scanning transmission electron microscopy (STEM). Corrosion behavior was assessed in room temperature saturated aqueous Mg(OH)2 solution with 1 wt.% NaCl. The goal of the effort was to assess the degree to which substrate alloy additions become enriched in the conversion coating, and how the conversion coating was impacted by subsequent electrocoating. Key findings included the enrichment of Al from AZ31B and Zr from ZE10A, respectively, into the conversion coating, with moderate corrosion resistance benefits for AZ31B when Al was incorporated. Varying degrees of increased porosity and modification of the initial conversion coating chemistry at the metal-coating interface were observed after electrocoating. These changes were postulated to result in degraded electrocoating protectiveness. These observations highlight the challenges of coating Mg, and the need to tailor electrocoating in light of potential degradation of the initial as-conversion coated Mg alloy surface.

Technological intervention for continuously cast billet of martensitic stainless ultra high strength steel

Substantial market exists for martensitic stainless Ultra High Strength Steel (UHSS) with 12–13 wt% Cr due to its high hardness and strength, moderate temperature tolerance and corrosion resistance. However, columnar crystals, center porosity, shrinkage cavity and surface quality of martensitic stainless UHSS depend on special continuous casting (CC) technology parameters. In order to control the quality of billets, an industrial plant trial for optimizing the process parameters in a square bloom continuous casting was performed, in which influences of caster parameters (such as casting speed, temperature, electromagnetic stirring (EMS), mold flux, secondary cooling) on the surface quality and solidification macrostructure of martensitic stainless UHSS were investigated. The results indicated that an excellent surface quality and a good billet solidification structure of martensitic stainless steel could be obtained with appropriate measures, in which all of subsurface crack and depression have disappeared, and the equiaxial crystals in the center of the martensitic stainless UHSS billet was up to 50%, even to the maximum of 57%, the central porosity was below level 1.5 and more than 90% of the central shrinkage cavities have reached to level 1.0.

Sliding Friction and Wear Characteristics of Grade 410 Martensitic Stainless Steel

Present work aimed at investigating the friction and wear of martensitic stainless steel of grade 410. This steel is used in nuclear industry for various moving components due to its high strength and moderate corrosion resistance. Properties of this material depend upon the heat treatment to which subjected to. The wear tests by sliding were performed on a pin on disk apparatus whose pin is in normalized and tempered condition. The counter face disc was machined from EN24 steel of high hardness in nature. The AISI 410 stainless steel wear rates were evaluated using Pin-on Disc Tribometer at various load and sliding speed. The worn pins were investigated by using scanning electron microscopy and surface profilometer.

Effect of Extrusion Ratio on Microstructure, Mechanical and Degradation Properties of Mg-2Zn-0.2Mn Biomedical Alloy

Magnesium is a biocompatible and biodegradable metal, which has attracted much interest in biomedical engineering. Cast magnesium alloy shows the low strength and plasticity at ambient temperature. Microstructure, mechanical properties and degradation properties of the extrusion pressed magnesium alloy have been investigated for biomedical application in detail by optical microscopes, mechanical properties testing and corrosion testing. The magnesium alloy ingot were extrude into bar at the different extrusion ratio. Optical microscopy observation has indicated that the grain size of the extruding has been significantly decreased from extrusion rate is 25, which has mainly contributed to the high tensile strength and good elongation. Hot extruding has provided moderate corrosion resistance, which has opened a new window for materials design, especially for biomedical.

Microstructure, mechanical and degradation properties of equal channel angular pressed pure magnesium for biomedical application

Magnesium is a biocompatible and biodegradable metal, which has attracted much interest in biomedical engineering. Pure magnesium shows the low strength and plasticity at ambient temperature. Microstructure, mechanical properties and degradation properties of the equal channel angular pressed pure magnesium have been investigated for biomedical application in detail by optical microscopes, mechanical properties testing and corrosion testing. The results have revealed that the processing temperature and routes are important factors that affect the properties of pure Mg by equal channel angular pressing. The two-step equal channel angular pressing processing (one pass at 360°C and three passes at 200°C) has been successfully applied to control the microstructure, mechanical and degradation properties of the pure Mg. Optical microscopy observation has indicated that the grain size of the as cast pure magnesium has been significantly decreased after equal channel angular extrusion, which has mainly contributed to the high tensile strength and good elongation. Equal channel angular pressed pure magnesium has provided moderate corrosion resistance, which has opened a new window for materials design, especially for biomedical.

The effect of heat treatment on mechanical properties and corrosion behavior of AISI420 martensitic stainless steel

Martensitic stainless steels are widely used for their good mechanical properties and moderate corrosion resistance. However, the need for superior properties in specific applications (e.g. steam generators, mixer blades, etc.) led to wide researches on the performance improvement of these steels. Heat treatment was recommended as one of the best ways to this regard hence the effects of astenitizing temperature and time, and tempering temperature on the microstructure, mechanical and corrosion properties of AISI420 have been studied. In the current work the experimental results showed that the austeitizing temperature significantly affects mechanical properties. The increase of tempering temperature led to precipitation of M7C3 and secondary hardening in the range of 400–500°C. SEM micrographs of the fracture surfaces showed a mixed fracture mechanism (brittle and ductile) at 200°C and 700°C and brittle mechanism at 500°C. The Polarization curves were not significantly affected by the increment of austenitizing temperature.

Some Major Features in Texture and Anisotropy Field

Some Major Features in Texture and Anisotropy Field

A New Austenitic FeMnAlCrC Alloy with High-Strength, High-Ductility, and Moderate Corrosion Resistance

In this study, a new austenitic Fe-28%Mn-9%Al-6%Cr-1.8%C (in mass%) alloy is developed. Because the alloy contains a high density of fine (Fe,Mn)3AlC carbides within the austenite matrix, the alloy in the as-quenched condition exhibits an excellent combination of strength and ductility comparable to that of the aged FeMnAlC alloys. In addition, owing to the formation of a layer of Cr and Al oxides in the passive film formed on the alloys, the corrosion potential Ecorr (−538 mV) and the pitting potential Epp (−25 mV) of the present alloy in 3.5% NaCl solution are considerably higher than the Ecorr (−920∼−789 mV) and Epp (−500∼−240 mV) values of the as-quenched and aged FeMnAlC alloys. Whereas the tensile strength of the present alloy is almost the same as that of conventional AISI 410 martensitic stainless steel, the present alloy possesses superior ductility than AISI 410 martensitic stainless steel. Furthermore, in 3.5% NaCl solution, the Epp (−25 mV) of the present alloy is noticeably higher than that (−250∼−100 mV) of the conventional AISI 410 martensitic stainless steel. These results indicate that the present alloy in the as-quenched condition can possess high-strength and high-ductility as well as moderate corrosion resistance.

English

The bio-degradability issue of polymer composites is studied to focus more on the use of the natural fibers such as bagasse, coir, sisal, jute etc. This has resulted in creation of more awareness about the use of natural fibers based materials mainly composites. In past decade there have been many efforts to develop composites to replace non decaying materials based products. The abundant availability of natural fiber in India gives attention on the development of natural fiber composites primarily to explore value-added application avenues. Reinforcement with natural fiber in composites has recently gained attention due to low cost, easy availability, low density, acceptable specific properties, ease of separation, enhanced energy recovery, CO2 neutrality, bio-degradability and recyclable in nature. Isophthalic polyester resin are a broad class of resins specification is selected to impart desired properties and corrosion resistance. These resins can be used for moderate corrosion resistance applications to a temperature range around 180 ₒ F. Isophthalic resins exhibits good resistance to water, acid, weak bases and hydrocarbons such as gasoline and oil. Agricultural wastes can be used to prepare fiber reinforced polymer composites for commercial use. Although glass and other synthetic fiber-reinforced plastics possess high specific strength, their fields of application are very limited because of their inherent higher cost of production. In this connection, an investigation has been carried out to make use of coir; a natural fiber abundantly available in India. This investigation discusses the use of coir fiber and its current status of research. Many references to the latest work on properties, processing and application have cited in this paper.

Hybrid corrosion‐resistant coatings analyzed using electrochemical noise

PurposeThe purpose of this paper is to study the corrosion of carbon steel without coating and when protected using three different hybrid coatings, i.e. a bi‐component polyurethane with nano‐particles of SiO2 with and without sacrificial anode particles, and a mono‐component polyurethane with SiO2 particles.Design/methodology/approachIn this investigation three different nano‐structured coatings are developed and applied to steel substrates and then tested for their corrosion resistance (defined as “Rn”), under a very aggressive medium (pH=1.5) in a dynamic system (loop reactor). Their performance is evaluated using an electrochemical noise (EN) resistance technique. The electrodes are connected to a potentiostat and measurements are recorded as per the EN technique over a 2,048 s duration at 0, 24, and 48 h intervals. Scanning electron microscopy (SEM) are obtained before and after the corrosion trials to characterize the control and the different coating systems.FindingsThe results show that a bicomponent coating, made up of alkyd resin and silica nanoparticles demonstrated the best performance, whereas the coating formed by SiO2 nanoparticles and polyurethane resin showed relatively low corrosion resistance. The inclusion of zinc nanoparticles in a third coating as sacrificial nano‐anodes led to segregation and resulted in moderate corrosion resistance. These results are confirmed by SEM observations.Originality/valueThe results obtained in this paper provide an insight to the understanding of the anticorrosion properties of three different hybrid coatings in a dynamic system (loop reactor).

Corrosion behaviour of Mg-alloy AZ91E with atypical alloying additions

Magnesium alloys are the lightest of all the structural metals with good strength/weight ratio and castability, however their application continues to be severely limited by relatively poor resistance to corrosion. Unlike most passivating metallic materials which develop their own protective surface oxide, magnesium suffers continued dissolution in neutral chloride solutions. AZ91E is a widely used magnesium-based alloy, which exhibits a balance between mechanical properties and moderate corrosion resistance; this work explores the affect of atypical alloying additions on the corrosion behaviour of this alloy. Results are presented in the form of a survey, along with an ensuing discussion of electrochemical test results and microscopy. It is noted that several elements are beneficial in improving corrosion resistance of AZ91E, while others accelerate corrosion rather dramatically.

Effect of Porosity on Ductility Variation in Investment Cast 17-4PH

The stainless steel alloy 17-4PH contains a martensitic microstructure and second phase delta ({delta}) ferrite. Strengthening of 17-4PH is attributed to Cu-rich precipitates produced during age hardening treatments at 900-1150 F (H900-H1150). For wrought 17-4PH, the effects of heat treatment and microstructure on mechanical properties are well-documented [for example, Ref. 1]. Fewer studies are available on cast 17-4PH, although it has been a popular casting alloy for high strength applications where moderate corrosion resistance is needed. Microstructural features and defects particular to castings may have adverse effects on properties, especially when the alloy is heat treated to high strength. The objective of this work was to outline the effects of microstructural features specific to castings, such as shrinkage/solidification porosity, on the mechanical behavior of investment cast 17-4PH. Besides heat treatment effects, the results of metallography and SEM studies showed that the largest effect on mechanical properties is from shrinkage/solidification porosity. Figure 1a shows stress-strain curves obtained from samples machined from castings in the H925 condition. The strength levels were fairly similar but the ductility varied significantly. Figure 1b shows an example of porosity on a fracture surface from a room-temperature, quasi-static tensile test. The rounded features represent the surfaces ofmore » dendrites which did not fuse or only partially fused together during solidification. Some evidence of local areas of fracture is found on some dendrite surfaces. The shrinkage pores are due to inadequate backfilling of liquid metal and simultaneous solidification shrinkage during casting. A summary of percent elongation results is displayed in Figure 2a. It was found that higher amounts of porosity generally result in lower ductility. Note that the porosity content was measured on the fracture surfaces. The results are qualitatively similar to those found by Gokhale et al. and Surappa et al. in cast A356 Al and by Gokhale et al. for a cast Mg alloys. The quantitative fractography and metallography work by Gokhale et al. illustrated the strong preference for fracture in regions of porosity in cast material. That is, the fracture process is not correlated to the average microstructure in the material but is related to the extremes in microstructure (local regions of high void content). In the present study, image analysis on random cross-sections of several heats indicated an overall porosity content of 0.03%. In contrast, the area % porosity was as high as 16% when measured on fracture surfaces of tensile specimens using stereology techniques. The results confirm that the fracture properties of cast 17-4PH cannot be predicted based on the overall 'average' porosity content in the castings.« less

Formation and characterization of borohydride reduced electroless nickel deposits

The present work aims to study the formation of electroless Ni-B deposits and evaluation of their characteristic properties. An alkaline bath having nickel chloride as the source of nickel and borohydride as the reducing agent was used to prepare the electroless Ni-B deposits. The influence of variation in bath constituents as well as operating conditions on the plating rate, and, the nickel and boron content, of the resultant Ni-B deposits were studied. Selected deposits were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), evolved gas analysis (EGA), vibrating sample magnetometer (VSM) and transmission electron microscope (TEM), respectively, for assessing the phase content, phase transformation behaviour, liberation of hydrogen during crystallization, saturation magnetic moment and micro-structural features. The corrosion resistance of Ni-B deposits, in 3.5% sodium chloride solution, both in as-plated and heat-treated (450 °C/1 h) conditions, was also evaluated by potentiostatic polarization and electrochemical impedance studies. XRD patterns reveal that Ni-B deposits of the present study are amorphous in as-plated condition and undergo phase transformation to crystalline nickel and nickel borides upon heat-treatment. DSC traces exhibit two exothermic peaks at 306 and 427 °C, corresponding to the phase transformation of amorphous Ni-B to crystalline nickel and Ni 3B phases and the transformation of a higher phase compound to Ni 3B and Ni 2B, respectively. TEM microstructures and EGA strongly support the occurrence of phase transitions at 306 and 427 °C. Electroless Ni-B deposits demonstrate a moderate corrosion resistance in 3.5% sodium chloride solution. The extent of corrosion resistance offered by electroless Ni-B deposits is relatively less compared to electroless Ni-9 wt.% P deposit.

AVESTA SHEFFIELD 248 SV

Abstract Avesta Sheffield 248 SV is a high-strength martensitic stainless steel. It combines high strength with good weldability and high toughness after welding. 248 SV is intended for applications that require high strength and toughness, good weldability, and moderate corrosion resistance. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-725. Producer or source: Avesta Sheffield AB.

Structure and properties of corrosion and wear resistant Cr-Mn-N steels

Steels containing about 12 pct Cr, 10 pct Mn, and 0.2 pct N have been shown to have an unstable austenitic microstructure and have good ductility, extreme work hardening, high fracture strength, excellent toughness, good wear resistance, and moderate corrosion resistance. A series of alloys containing 9.5 to 12.8 pct Cr, 5.0 to 10.4 pct Mn, 0.16 to 0.32 pct N, 0.05 pct C, and residual elements typical of stainless steels was investigated by microstructural examination and mechanical, abrasion, and corrosion testing. Microstructures ranged from martensite to unstable austenite. The unstable austenitic steels transformed to α martensite on deformation and displayed very high work hardening, exceeding that of Hadfield’s manganese steels. Fracture strengths similar to high carbon martensitic stainless steels were obtained while ductility and toughness values were high, similar to austenitic stainless steels. Resistance to abrasive wear exceeded that of commercial abrasion resistant steels and other stainless steels. Corrosion resistance was similar to that of other 12 pct Cr steels. Properties were not much affected by minor compositional variations or rolled-in nitrogen porosity. In 12 pct Cr-10 pct Mn alloys, ingot porosity was avoided when nitrogen levels were below 0.19 pet, and austenitic microstructures were obtained when nitrogen levels exceeded 0.14 pct.

Blackening of aluminium-zinc (galvalume) coatings for solar energy utilization

The authors have reported a method for immersion blackening of Galvalume coatings for use as a selective surface for solar collectors. Such coatings have a solar absorptance (α) of 0.90–0.92 and thermal emittance (ϵ) of 0.25–0.40. The coating has moderate corrosion resistance. In order to improve this, a post-treatment is necessary. The post-treated coatings in dichromate solution offer good corrosion resistance. Thermal cycling tests show that the coatings are stable to 220°C. Tape tests show that the coating is strongly adherent.

METGLAS MBF-17/MBF-17A

Abstract METGLAS MBF-17A is a brazing foil in ductile, flexible metallic-glass form (A similar grade, MBF-17, is identical except that it has larger dimensional tolerances). It provides high strength at both elevated and room temperatures with moderate oxidation and corrosion resistance. An example of application is brazing turbine blades in truck engines where high strength at high temperatures is required. This datasheet provides information on composition, physical properties, and microstructure. It also includes information on forming, heat treating, and joining. Filing Code: Ni-303. Producer or source: Allied Corporation.