Effects of Nickel and Chromium Additions on Microstructure of P/M 316L Stainless Steels

2017 ◽  
Vol 891 ◽  
pp. 452-457
Author(s):  
Seksak Asavavisithchai ◽  
Panyawat Wangyao ◽  
Fonthip Tangmon ◽  
Pipat Tangsatapornpad
Keyword(s):  
High Pressure ◽  
Stainless Steel ◽  
Oxidation Resistance ◽  
Working Conditions ◽  
Stainless Steels ◽  
Sintering Temperature ◽  
Optical Microscope ◽  
Hydrogen Atmosphere ◽  
Microstructural Development ◽  
Σ Phase

The present study aims to investigate the effects of Ni and Cr additions on microstructure of P/M 316L stainless steels. The optimum content of both elements to maximize the oxidation resistance of the stainless steel with minimum σ phase formation and microstructural development in various sintering times are also examined. The 316L samples were produced by homogeneously mixing Ni and Cr powders in various contents, followed by cold compaction at high pressure for 30 s. The solutioning process was performed at 1300°C for 45 s under hydrogen atmosphere. The sintering temperature was at 800°C and the sintering times were selected at 200, 400 and 600 hrs, in order to simulate working conditions. The development of microstructure was examined through optical microscope. It is found that the addition of Ni and Cr resulted in the formation of different porosity contents. The porosity increases when the content of the powders increases.

Stainless Steels With Improved Oxidation Resistance for Recuperators

2004 ◽  
Vol 128 (2) ◽  
pp. 370-376 ◽  
Author(s):  
Bruce A. Pint
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Oxidation Resistance ◽  
Stainless Steels ◽  
Lower Cost ◽  
Exhaust Gas ◽  
New Materials ◽  
Excellent Corrosion Resistance ◽  
Gas Environment

New materials are being evaluated to replace type 347 stainless steel in microturbine recuperators operating at higher temperatures in order to increase the efficiency of the microturbine. Commercial alloys 120 and 625 are being tested along with potentially lower cost substitutes, such as Fe-20Cr-25Ni and Fe-20Cr-20Ni. Long-term testing of these materials at 650–700 °C shows excellent corrosion resistance to a simulated exhaust gas environment. Testing at 800 °C has been used to further differentiate the performance of the various materials. The depletion of Cr from foils of these materials is being used to evaluate the rate of attack. Although those alloys with the highest Ni and Cr contents have longer lives in this environment, lower alloyed steels may have sufficient protection at a lower cost.

Producing HP Pump Barrels Utilizing Powder Metallurgy and Hot Isostatic Pressing

2009 ◽  
Author(s):  
Martin Bjurstro¨m ◽  
Carl-Gustaf Hjorth
Keyword(s):  
High Pressure ◽  
Stainless Steel ◽  
Stainless Steels ◽  
Hot Isostatic Pressing ◽  
Austenitic Stainless Steels ◽  
Pressure Vessels ◽  
Uniform Structure ◽  
Isostatic Pressing ◽  
Near Net Shape ◽  
Hip Process

The fabrication of near net shape powder metal (PM) components by hot isostatic pressing (HIP) has been an important manufacturing technology for steel and stainless steel alloys since about 1985. The manufacturing process involves inert gas atomization of powder, 3D CAD capsule design, sheet metal capsule fabrication and densification by HIP in very large pressure vessels. Since 1985, several thousand tonnes of parts have been produced. The major applications are found in the oil and gas industry especially in offshore applications, the industrial power generation industry, and traditional engineering industries. Typically, the components replace castings, forgings and fabricated parts and are produced in high alloy grades such as martensitic steels, austenitic stainless steels, duplex (ferritic/austenitic) stainless steels and nickel based superalloys. The application of PM/HIP near net shapes to pump barrels for medium to high pressure use has a number of advantages compared to the traditional forging and welding approach. First, the need for machining of the components is reduced to a minimum and welding during final assembly is reduced substantially. Mechanical properties of the PM/HIP parts are isotropic and equal to the best forged properties in the flow direction. This derives from the fine microstructure using powder powder and the uniform structure from the HIP process. Furthermore, when using the PM HIP process the parts are produced near net shape with supports, nozzles and flanges integrated. This significantly reduces manufacturing lead-time and gives greater design flexibility which improves cost for the final component. The PM HIP near net shape route has received approval from ASTM, NACE and API for specific steel, stainless steel and nickel base alloys. This paper reviews the manufacturing sequence for PM near net shapes and discusses the details of several successful applications. The application of the PM/HIP process to high pressure pump barrels is highlighted.

Influence of Nitrogen on Oxidation Resistance of Automotive Steel Grades

2020 ◽  
Vol 835 ◽  
pp. 83-92
Author(s):  
Saeed Ghali ◽  
Mamdouh Eissa ◽  
Hoda El-Faramawy ◽  
Azza Ahmed ◽  
Fathy Baiomy ◽  
...  
Keyword(s):  
Oxidation Resistance ◽  
Stainless Steels ◽  
Oxidation Process ◽  
Diffusion Mechanism ◽  
Solution Treatment ◽  
Mass Gain ◽  
Optical Microscope ◽  
Partial Replacement ◽  
Steel Grades ◽  
Automotive Steel

With the objective of partial and total replacement of nickel by nitrogen in austenitic exhausted valve steel X45CrNiW18-9, a program of work with series of experimental heats was designed. Experimental heats were carried out in 10 Kg. induction furnace under nitrogen pressure. The chemical composition of produced stainless steels was determined. The produced automotive steel grades were forged. The nitrogen contents were determined. The produced forged stainless steels were subjected to solution treatment at 1050 °C for 1 hour, followed by water cooling. Isothermal oxidation test is used to detect the behavior of new grades at different temperatures in air for solution treated stainless steels. The mass gain was measured for samples exposed to air at temperatures (500 °C, 600 °C, 700 °C, 800°C) for different time intervals, up to 1000 hrs. The oxide layer thickness for two selected steels was investigated by using optical microscope. XRD was used to detect types of oxides which are formed during oxidation process at 800 °C for 1000 hrs for represented investigated exhausted valve steels. Scanning Electron Microscope was used to make scan steels surface, after heating at 500 °C and 800 °C for l000hr. The mechanism of the oxidation of developed steels was investigated. It was found controlled by diffusion mechanism and the kinetic of oxidation process is parabolic. Oxidation rate of the investigated stainless steels for times, up to 8 h and between 200 andl000 h, at all investigated temperatures (500 °C - 800 °C), is parabolic and the oxidation is diffusion controlled. While in the time region 10 to 200 h, it obeys combined mechanisms. Partial replacement of nickel, by nitrogen, improves the oxidation resistance in air at temperature range 500°C - 800°C.

Producing HP Pump Barrels Utilizing Powder Metallurgy and Hot Isostatic Pressing

2009 ◽  
Author(s):  
Martin Bjurstro¨m ◽  
Carl-Gustaf Hjorth
Keyword(s):  
High Pressure ◽  
Stainless Steel ◽  
Stainless Steels ◽  
Hot Isostatic Pressing ◽  
Austenitic Stainless Steels ◽  
Pressure Vessels ◽  
Uniform Structure ◽  
Isostatic Pressing ◽  
Near Net Shape ◽  
Hip Process

The fabrication of near net shape powder metal (PM) components by hot isostatic pressing (HIP) has been an important manufacturing technology for steel and stainless steel alloys since about 1985. The manufacturing process involves inert gas atomization of powder, 3D CAD capsule design, sheet metal capsule fabrication and densification by HIP in very large pressure vessels. Since 1985, several thousand tonnes of parts have been produced. The major applications are found in the oil and gas industry especially in offshore applications, the industrial power generation industry, and traditional engineering industries. Typically, the components replace castings, forgings and fabricated parts and are produced in high alloy grades such as martensitic steels, austenitic stainless steels, duplex (ferritic/austenitic) stainless steels and nickel based superalloys. The application of PM/HIP near net shapes to pump barrels for medium to high pressure use has a number of advantages compared to the traditional forging and welding approach. First, the need for machining of the components is reduced to a minimum and welding during final assembly is reduced substantially. Mechanical properties of the PM/HIP parts are isotropic and equal to the best forged properties in the flow direction. This derives from the fine microstructure using powder powder and the uniform structure from the HIP process. Furthermore, when using the PM HIP process the parts are produced near net shape with supports, nozzles and flanges integrated. This significantly reduces manufacturing lead-time and gives greater design flexibility which improves cost for the final component. The PM HIP near net shape route has received approval from ASTM, NACE and API for specific steel, stainless steel and nickel base alloys. This paper reviews the manufacturing sequence for PM near net shapes and discusses the details of several successful applications. The application of the PM/HIP process to high pressure pump barrels is highlighted.

Examination of the Orientation Relationships between the Main Phases of Duplex Stainless Steel by EBSD

2007 ◽  
Vol 537-538 ◽  
pp. 297-302
Author(s):  
Tibor Berecz ◽  
Péter János Szabó
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Stainless Steels ◽  
Electron Backscatter Diffraction ◽  
Duplex Stainless Steels ◽  
Alloying Elements ◽  
Orientation Relationships ◽  
Σ Phase ◽  
Electron Backscatter ◽  
Backscatter Diffraction

Duplex stainless steels are a famous group of the stainless steels. Duplex stainless steels consist of mainly austenitic and ferritic phases, which is resulted by high content of different alloying elements and low content of carbon. These alloying elements can effect a number of precipitations at high temperatures. The most important phase of these precipitation is the σ-phase, what cause rigidity and reduced resistance aganist the corrosion. Several orientation relationships have been determined between the austenitic, ferritic and σ-phase in duplex stainless steels. In this paper we tried to verify them by EBSD (electron backscatter diffraction).

Zinc diffusion induced precipitation of σ-phase in austenitic stainless steel

2019 ◽  
Vol 116 (6) ◽  
pp. 618
Author(s):  
Nega Setargew ◽  
Daniel J. Parker
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Stainless Steels ◽  
Intermetallic Phase ◽  
Austenitic Stainless Steels ◽  
Austenite Matrix ◽  
Σ Phase ◽  
Intermediate Phases ◽  
Zinc Diffusion

Zinc diffusion-induced degradation of AISI 316LN austenitic stainless steel pot equipment used in 55%Al-Zn and Zn-Al-Mg coating metal baths is described. SEM/EDS analyses results showed that the diffused zinc reacts with nickel from the austenite matrix and results in the formation of Ni-Zn intermetallic compounds. The Ni-Zn intermetallic phase and the nickel depleted zones form a periodic and alternating layered structure and a mechanism for its formation is proposed. The role of cavities and interconnected porosity in zinc vapour diffusion-induced degradation and formation of Ni-Zn intermediate phases is also discussed. The formation of Ni-Zn intermediate phases and the depletion of nickel in the austenite matrix results in the precipitation of σ-phase and α-ferrite in the nickel depleted regions of the matrix. This reaction will lead to increased susceptibility to intergranular cracking and accelerated corrosion of immersed pot equipment in the coating bath. Zinc diffusion induced precipitation of σ-phase in austenitic stainless steels that we are reporting in this work is a new insight with important implications for the performance of austenitic stainless steels in zinc containing metal coating baths and other process industries. This new insight will further lead to improved understanding of the role of substitutional diffusion and the redistribution of alloying elements in the precipitation of σ-phase in austenitic stainless steels.

scholarly journals Influence of Coolant Pressure Size on Surface Roughness when Stainless Steel Machining

2019 ◽  
Vol 299 ◽  
pp. 04002
Author(s):  
Robert Cep ◽  
Lenka Cepova ◽  
Cristina Stefana Borzan ◽  
Jiri Kasal ◽  
Marek Sadilek ◽  
...  
Keyword(s):  
Surface Roughness ◽  
High Pressure ◽  
Stainless Steel ◽  
Control Valve ◽  
Pressure Control ◽  
Optical Microscope ◽  
Contact Method ◽  
External Cooling ◽  
Pressure Control Valve ◽  
Valve Housing

The paper is focused on the influence of the coolant pressure on the surface roughness of the workpiece when machining stainless steels. The components were machined on a STAR SR-32J dual spindle machining center and an external cooling unit HYTEK CHAV 160/150-AF-F-OL was used for cooling. Two stainless steel components were investigated, namely the gas control valve rod and the high-pressure control valve housing, which require low roughness Ra after machining (less than 0.375 and 0.25 micrometers respectively). The first component was tested at 8 different pressures in the range of 150 bar - 10 bar and the second component at 4 different pressures in the range of 120 bar - 10 bar. The roughness parameters were measured by the contact method using the MITUTOYO Surftest SJ-410 Roughness Tester and the Alicona InfiniteFocus optical microscope. Based on these sample input parameters, it was evaluated howmuch the pressure affects the surface quality or suggested its reduction due to the high cost of operation of the external high-pressure equipment.

Microstructure Evolution in Isothermal Heat Treatment of 0Cr32Ni7Mo4NDuplex Stainless Steel

2014 ◽  
Vol 789 ◽  
pp. 314-319
Author(s):  
Yu Lai Chen ◽  
Hong He ◽  
Fei Fang
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Microstructure Evolution ◽  
Volume Fraction ◽  
Decomposition Reaction ◽  
Optical Microscope ◽  
Isothermal Heat Treatment ◽  
Σ Phase ◽  
Temperature Range ◽  
Δ Phase

The microstructure evolution of as-cast 0Cr32Ni7Mo4N hyper duplex stainless steel during the isothermal heat treatment in the temperature range of 800°C-1300°Cwas studied in the present investigation. The morphologies and precipitates were observed and determined by using optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that eutectoid decomposition reaction (δ→σ+γ2) take place in ferrite (δ) phase during isothermal heat treatment in the temperature range of 800°C-1000°C. Sigma (σ) phase and secondary austenite (γ2) phase coexist as cellular structure. Lamellar Cr2N precipitates in δ phase mostly when isothermal heat treatment at 800°Cand 850°C, while it only appears in γ phase between 900°C and 1050°C. As the annealing temperature rising, the quantity of σ phase, Cr2N and γ2 phase decreases. The volume fraction ratio of ferrite and austenite is stable between 1100°C and 1300°C, and γ → δ transformation is hard to occur.

Microstructure and Mechanical Properties of the Stainless Steels Obtained by Sintering Mixtures of AISI 316L and Silicon Powders

2006 ◽  
Vol 513 ◽  
pp. 35-50
Author(s):  
K. Sikorski ◽  
Agnieszka Szymańska ◽  
M. Sekuła ◽  
D. Kowalczyk ◽  
Jan Kazior ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Austenitic Steel ◽  
Stainless Steels ◽  
Hydrogen Atmosphere ◽  
Aisi 316L ◽  
Microstructure And Mechanical Properties ◽  
Steel Aisi

The aim of the study was to obtain a ferritic-austenitic stainless steel through sintering of the mixture of austenitic steel AISI 316L powders with silicon in the amount ranging from 1 to 7%. The pressed mixtures were sintered at 1240oC for 60 minutes under hydrogen atmosphere. The results of the silicon admixture on the density, porosity, microstructure and mechanical properties of the sintered specimens are discussed.

scholarly journals Surface Treatment Proposals for the Automotive Industry by the Example of 316L Steel

2018 ◽  
Vol 1 (1) ◽  
pp. 369-376 ◽  
Author(s):  
Agata Dudek ◽  
Barbara Lisiecka
Keyword(s):  
Stainless Steel ◽  
Stainless Steels ◽  
Scratch Test ◽  
Optical Microscope ◽  
Atmospheric Plasma ◽  
Stainless Steel Surface ◽  
Industrial Sectors ◽  
Steel Modification ◽  
316L Steel ◽  
Sintered Stainless Steel

Abstract Nowadays, stainless steels are very interesting and promising materials with unique properties. They are characterized high mechanical strengths, high toughness and good corrosion resistance, so that can be used in many industrial sectors. An interesting alternative to steels obtained using the conventional methods is sintered stainless steel manufactured using the powder metallurgy technology. AISI 316L stainless steel is one of the best-known and widely used austenitic stainless steel. Modification of surface properties of stainless steels, in particular by applying the Cr3C2 coating is becoming more and more popular. The technique of atmospheric plasma spraying (APS) was used to deposit Cr3C2 - NiAl powder on stainless steel surface. In this study presents arc surface remelting of two types of stainless steel was used by GTAW method in order to improve function and usability these materials. The results of optical microscope metallographic, hardness and scratch test are presented. The main assumption for this study was to analyze the microstructure and hardness after remelting and alloying the surface of 316L steel (using GTAW method) with current intensity 50 A.

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