Precipitation of carbides and sigma phase in AISI type 446 stainless steel under working conditions

Guimarães, A.A.; Mei, Paulo Roberto

doi:10.1016/j.jmatprotec.2004.04.341

Cited by 40 publications

(18 citation statements)

References 7 publications

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“…A main conclusion that can be obtained from these experimental data is that a longer time of thermal aging makes possible a higher amount of sigma phase and, as a result (see Table 2), an increase of the resultant microhardness values are obtained. However, this experimental result related to this sigma phase is lower than reported by Guimaraes et al [46], who measured values of 522 HV in an AISI 446 stainless steel.…”

Section: Microhardness Measurementscontrasting

confidence: 77%

“…These specific values of nanohardness are higher than other values presented in previous works from 3.2 GPa to 4.4 GPa [26,27]. The main reason to justify this observation is based on work-hardening experimental result related to this sigma phase is lower than reported by Guimaraes et al [46], who measured values of 522 HV in an AISI 446 stainless steel. …”

Section: Nanoindentation Hardness Measurements In Austenite and Ferricontrasting

confidence: 44%

“…Metals 2017, 7, 219 7 of 11 experimental result related to this sigma phase is lower than reported by Guimaraes et al [46], who measured values of 522 HV in an AISI 446 stainless steel. …”

Section: Microhardness Measurementsmentioning

confidence: 63%

“…A combination of two main reasons might explain the low nanoindentation hardness and the high relative standard deviation of the results. Firstly, it has been previously reported [46] that the sigma phase may present a wide range of hardness values due to the complexity of this structure. Secondly, nanoindentation results are strongly dependent on the surface finish, especially affecting the scattering of the results with respect to the average value [47] but not only, since both the hardness and Young's modulus are strongly influenced.…”

Section: Nanoidentation Hardness Measurements In Sigma Phasementioning

confidence: 99%

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Effect of the Temperature in the Mechanical Properties of Austenite, Ferrite and Sigma Phases of Duplex Stainless Steels Using Hardness, Microhardness and Nanoindentation Techniques

Argandoña¹,

Palacio

Berlanga

et al. 2017

Metals

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Abstract:The aim of this work is to study the hardness of the ferrite, austenite and sigma phases of a UNS S32760 superduplex stainless steel submitted to different thermal treatments, thus leading to different percentages of the mentioned phases. A comparative study has been performed in order to evaluate the resulting mechanical properties of these phases by using hardness, microhardness and nanoindentation techniques. In addition, optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been also used to identify their presence and distribution. Finally, the experimental results have shown that the resulting hardness values were increased as a function of a longer heat treatment duration which it is associated to the formation of a higher percentage of the sigma phase. However, nanoindentation hardness measurements of this sigma phase showed lower values than expected, being a combination of two main factors, namely the complexity of the sigma phase structure as well as the surface finish (roughness).

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Section: Microhardness Measurementscontrasting

confidence: 77%

Section: Nanoindentation Hardness Measurements In Austenite and Ferricontrasting

confidence: 44%

“…Metals 2017, 7, 219 7 of 11 experimental result related to this sigma phase is lower than reported by Guimaraes et al [46], who measured values of 522 HV in an AISI 446 stainless steel. …”

Section: Microhardness Measurementsmentioning

confidence: 63%

Section: Nanoidentation Hardness Measurements In Sigma Phasementioning

confidence: 99%

See 2 more Smart Citations

Effect of the Temperature in the Mechanical Properties of Austenite, Ferrite and Sigma Phases of Duplex Stainless Steels Using Hardness, Microhardness and Nanoindentation Techniques

Argandoña¹,

Palacio

Berlanga

et al. 2017

Metals

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show abstract

“…These chromium carbides, type M7C3 and M23C6 (M = Fe, Cr) [11,12], will deplete the surrounding matrix of chromium and make the alloy more sensitive to intergranular corrosion. This is easy to understand since these chromium carbides present a chromium content between 24% and 60% [13,14]. These carbide networks usually appear when the alloy is cooled very slowly through high temperature ranges, in which the carbon-rich austenite rejects the carbon (maximum carbon solubility of 2.06% at 1148 • C in the austenite) as grain boundary networks instead of dispersed particles [7,8,10].…”

Section: Introductionmentioning

confidence: 99%

Dissolution of Grain Boundary Carbides by the Effect of Solution Annealing Heat Treatment and Aging Treatment on Heat-Resistant Cast Steel HK30

Silva

Santos

Gouveia

2017

Metals

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Abstract:Decreasing the weight of heavy-duty vehicles is an ongoing concern. However, the need to deal with high temperatures in components such as manifolds imposes, by itself, some restrictions regarding material selection, being further limited when other required properties (e.g., functional, manufacturing or cost requirements) are taken into account. Cast austenitic stainless steels may represent a good choice in this context but the existence of concentrated chromium carbides can generate undesirable results. A good combination of heat treatments can be applied to cast heat-resistant austenitic stainless steels, in an effort to achieve the dispersion of fine carbides, consequently improving their microstructure, mechanical properties and creep resistance. In this work, an austenitic stainless steel usually used in high temperature applications was characterized and subjected to solution annealing and aging heat treatments. The material analyzed was the austenitic cast stainless steel HK30 and the goals of the work were to evaluate the effects of solution annealing heat treatments on the dissolution of grain boundary chromium carbides and the effects of aging treatments on creep resistance. The results show that the elimination of grain boundary chromium carbides is possible by applying a solution annealing heat treatment. Additionally, the precipitation of fine dispersed carbides is obtained after the aging treatment with an increase of hardness and, consequently, an expected improvement of creep resistance. Thus, the novelty presented by this work consists of selecting the best heat treatment combination in order to promote dispersion of carbides, thus avoiding further crack nucleation phenomena when parts are cyclically subjected to load and unload; this work also found the most adequate mechanical properties and achieved corrosion resistance regarding the application in heavy-duty vehicle components subjected to mechanical and thermal fatigue. By discovering methods of improving the properties of cast materials, large savings can be made both in terms of production costs as well as in the overall weight of the components.

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Intermetallic Compounds

2009

Chemistry and Physics of Mechanical Hardness

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INTERMETALLIC COMPOUNDS alloys, and, correcting his former view, introduced the word " eutectic " to denote the mixtures of constant minimum freezing-point. 5 The assigning of a chemical formula to a eutectic alloy is to be found even in some recent work, where freezing-point curves have been determined experimentally without a proper comprehension of their meaning. This false assumption of chemical compounds is not to be confused with the quite legitimate attempt to discover definite atomic or molecular ratios in eutectic mixtures, the heterogeneous nature of the eutectic equilibrium being fully recognized. 6 A more promising approach was made in a different way. So far back as 1839, Karsten 7 observed the change of colour of alloys of copper and zinc with the composition, and found that the action of acids on those alloys exhibited a discontinuity at the point at which copper and zinc were present in equal proportions. He therefore suggested the presence of a compound in the series. Attempts were next made to isolate definite compounds from alloys by a process of partial fusion and of mechanical separation of the solid and liquid phases. The first extensive experiments of this kind are due to Crookewit, 8 who examined in this way many amalgams, and also alloys of copper with tin, lead, zinc, etc. This plan was adopted by many other investigators, most of whom employed amalgams, on account of their low meltingpoint and the consequent facility of handling. The validity of this method is discussed below (p. 27). Calvert and Johnson 9 attempted in the same way to isolate the chemical compounds which they assumed to be present in alloys, accompanied by an excess of one or the other component, but their later work 10 opened up a more fruitful field of investigation. By determining the values of certain physical constants, such as the thermal and electrical conductivity, hardness, and specific gravity of a number of alloys in a given series, and observing the manner in which the property selected varied with the composition of the alloys, they established the fact that discontinuities occur, which were rightly attributed to the presence of intermetallic compounds. The same course was followed, with important results, by Matthiessen and his collaborators, whose very extensive and accurate determinations of many of the physU cal properties of alloys placed the subject on a new basis. 11 The as native minerals. So little success has been met with in this direction, however, that our knowledge of the properties of such compounds is mainly derived from a study of the alloys in which they occur. The succeeding sections are therefore devoted to a consideration of the influence which the presence of intermetallic compounds exerts on some of the most important physical properties of alloys. It is also shown that the systematic investigation of certain properties, especially of the electrical conductivity and the thermo-electric power, affords the most delicate means in * The practical methods employed in investigations of this...

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Precipitation of carbides and sigma phase in AISI type 446 stainless steel under working conditions

Cited by 40 publications

References 7 publications

Effect of the Temperature in the Mechanical Properties of Austenite, Ferrite and Sigma Phases of Duplex Stainless Steels Using Hardness, Microhardness and Nanoindentation Techniques

Effect of the Temperature in the Mechanical Properties of Austenite, Ferrite and Sigma Phases of Duplex Stainless Steels Using Hardness, Microhardness and Nanoindentation Techniques

Dissolution of Grain Boundary Carbides by the Effect of Solution Annealing Heat Treatment and Aging Treatment on Heat-Resistant Cast Steel HK30

Intermetallic Compounds

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