CA1127940A - Method of making surface layers with improved corrosion properties on articles of iron-chromium alloys, and a surface layer made by the method - Google Patents
Method of making surface layers with improved corrosion properties on articles of iron-chromium alloys, and a surface layer made by the methodInfo
- Publication number
- CA1127940A CA1127940A CA307,885A CA307885A CA1127940A CA 1127940 A CA1127940 A CA 1127940A CA 307885 A CA307885 A CA 307885A CA 1127940 A CA1127940 A CA 1127940A
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- Prior art keywords
- surface layer
- chromium
- article
- iron
- range
- Prior art date
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/10—Oxidising
- C23C8/12—Oxidising using elemental oxygen or ozone
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/10—Oxidising
- C23C8/12—Oxidising using elemental oxygen or ozone
- C23C8/14—Oxidising of ferrous surfaces
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method for making surface layers with improved cor-rosion properties on articles of iron-chromium alloys is disclosed.
By enriching the surface of iron-chromium alloys, high corrosion resistance may be obtained without alloying the complete steel matrix, The method includes heating the articles in an oxygen atmosphere having a vacuum in the range of 10-1 to 10-8 mm Hg, to a temperature at which diffusion of reactive alloy components com-bine with oxygen on a surface layer of the article, The tempe-rature is such that all the other properties of the article are maintained, The temperature is maintained until the surface layer is oxidized to a thickness in the range of 10-9 to 10-7 m, whereby the surface layer forms part of the matrix of the metal alloy,
A method for making surface layers with improved cor-rosion properties on articles of iron-chromium alloys is disclosed.
By enriching the surface of iron-chromium alloys, high corrosion resistance may be obtained without alloying the complete steel matrix, The method includes heating the articles in an oxygen atmosphere having a vacuum in the range of 10-1 to 10-8 mm Hg, to a temperature at which diffusion of reactive alloy components com-bine with oxygen on a surface layer of the article, The tempe-rature is such that all the other properties of the article are maintained, The temperature is maintained until the surface layer is oxidized to a thickness in the range of 10-9 to 10-7 m, whereby the surface layer forms part of the matrix of the metal alloy,
Description
794~
Method of making surface layers with improved corrosion properties on articles of iron-chromium alloys, and a surface layer made by the method -This invention relates to a method of improving the corrosion propert-ies of chromium-alloyed steels.
The alloying of, for example, chromium, molybdenum, silicon or aluminium into steel in order to improve the corrosion properties of the steel involves substantial manufacturing C08t8- The corrosion properties of a steel being determined by the condition of the steel surface, it is of interest to enrich the steel surface in respect of certain alloy-ing components, which have a positive effect or the corrosion resist-ance of the steel. In this way, either the amount of alloying compon-ents in the steel matrix could be decreased in order to achieve a cert-ain corrosion resistance, or the corrosion resistance for a given composition in the steel matrix could be increased.
For obtaining a surface layer on a substrate where the structure and composition in the surface layer differs from the substrate, one can choose between a number of known methods, for example metallization, electrolytic precipitat~on or cladding. The principle here is to apply the desired surface layer externally to the substrate ~ia, for example, '` . ' 1~Z7940 adsorption, condensation or precipitation on the surface of the substrate from a gaseous or liquid phase.
According to the present invention a surface layer with substantially improved corrosion properties is obtained thereby that, distinguished from the methods mentioned above, an oxide is formed on the surface of the substrate where the oxidized material is comprised in the substrate.
The present invention, thus, relates to a method of making a surface layer with impro~ed corrosion properties on articles of iron-chromium alloys where the article i8 heated in an oxygen containing atmosphere with vacuum.
The invention is characterized in that the article is heated in an oxygen containing gaseous atmosphere with a total vacuum of about 10 1 down to 10 8 mm Hg, preferably about 10 5 mm Hg, to a temperature, at which diffusion of the most reactive slloying component or compon-ents, primarily chromium, with respect to its tendency of combining with oxyeen, to the surface becomes perceptible, and at which temper-ature the remaining properties of the alloy substantially are maint-ained, and that the described condition for the article is maintained until a surface layer containing oxidized chromium has grown to a thickness of preferably 10 9 - 1a 7 m,whereby the resulting surface layer with respect to structure and composition transforms by degrees from a condition on the surface to a condition in the matrix of the metal alloy.
This invention, thus, distinguished from conventional methods where in all cases a surface layer is applied externally to a su~strate, relates to a method, at which the surface layer is made by means of alloying components comprised in the substrate. The surface layer thereby is 1~Z7940 formed by heating the substrate, which is a chromium steel, in a gaseous atmosphere at vacuum containing a low and well-controlled oxygen content.
At heating in gaseous atmosphere with vacuum, a preferential enrich-ment to the surface of the chromium steel takes place of that alloying component or those alloying components, which have the strongest tendency of forming compounds with oxygen present on the fiurface of the chromium steel. The term oxygen present on the steel surface also includes the oxygen compr-sed in the very thin oxide film, which usually exists on the chromium steel surface prior to the heating in the gaseous atmosphere, and the small but very well controlled amount of oxygen, which exists in the gaseous atmosphere and reaches to the surface of the article.
The temperature, to which the article is heated, is chosen so that diffusion of the most reactive alloying component or components to the surface becomes perceptible. For iron-chromium alloys the diffusion takes place above a temperature of about 300C. The temperature also must be chosen so that other properties characteristic of the metal alloy are not deteriorated. This temperature is for iron-chromium alloys below about 600 C, because above said temperature carbide is precipitated in the grain boundaries, and in certain cases pha6e transformations can occur. The stated lower as well as the stated higher temperature, of course, are individual for each type of iron-chromium alloy, but a suitable heating temperature for the majority of iron-chromium alloys is between 300C and 600C. A preferred temper-ature is about ~00 C. Surface layers, thus,with improved corrosion properties have been observed after heating in gaseous atmosphere in the range 300C-550C, with optimum results about 475C.
~12794~
The amount of oxygen being present on the surface of the article is to be adjusted both to the heating temperature and to the desired properties of the surface layer. In many applications the oxygen amount level should be so low that substantially only one of the alloying components of the arti-cle is capable to react with oxygen For effecting such a low supply of oxygen to the article surface, normally vacuum conditions are required, which depending on metal alloy and surface layer can extend from tenths of millimeters Hg to ultra-high vacuum conditions (~10 8 mm Hg). The heating can incertain cases also be carried out in protective atmosphere, but then the difficulties of maintaining a sufficiently low and well-controlled oxygen level are more obvious.
For obtaining a good result, said pressure range implies a total vacuum of about 10 - 10 mm Hg A preferred pressure is about 10 mm Hg. According to the invention, the article is to be treated at said pressure and temperature until a sur-face layer containing oxidized chromium has grown to a thickness of about 10 - 10 m and preferably 10 - 10 m, which, thus, is an extremely thin surface layer. The time of such a treatment amounts to a number of hours, as is exemplified in greater detail below.
The time of heat treatment, exclusive of heating and cooling periods, is to be adjusted, of course, to the amount of oxygen in the gaseous atmosphere and to the heating temperature. It was found that this implies heating times in the range one half to ten hours, with optimum results at about three hours~
The surface layer thus obtained, with a thickness varying be-tween 10 and 10 7 m, shows a structure and a composition which by degrees transforms from a condition in the outermost atom layer of the surface layer ~Z7940 to a condition characterizing the matrix of the metal alloy.
The improved corrosion properties are attributed to an obser~ed enrich-ment of alloying comp~nents, sùch as chromium, molybdenum or titanium in the surface layers thus formed.
As a consequence of the gradual transformation from substrate to sur-face layer, the surface layer i6 characterized by good adherence to the substrate. The transformation further takes place without great accumulations of defects or other material deficiencies. A further consequence of the fact that the surface layer is applied to the sub-strate internally and under vacuum conditions, is that the coat is the ~ame all over the article surface, thufi also in inward bulges and other surface areas where an external application would be rendered difficult by shading effects.
A surface layer made according to the present-method on articles of iron-chromium alloys, which were heated in an oxygen containing gaseous atmosphere under low pressure, thu6, comprises chromium of a higher concentration than the article in general, which chromium is oxidized entirely or partially, and which surface layer has a thickness of about 10-1 _ 10-6 m, preferably 10 9 - 10 m.
Examples:
I
a) A plate of iron-chromium alloy containing 5% chromium was exposed on a ~urface of 20 mm to tap water for 2 hours. After 2 hours a corrcsion current of 10 5 A was obtained.
b) A plate similar to that in a) was exposed according to the invention to a treatment consisting of heating at 475C for 6 hours at the total pressure 1,8 x 10 5 mm Hg. The resulting surface layer was characterized ~127940 by a gradual transformation from a high chromium content farthest outwardly in the surface layer to the low chromium content in the matrix of the alloy. When 20 mm2 of this treated surface were exposed to tap water, after 2 hours a corrosion current of 10 7 A was obtained.
The one hundred times lower corrosion current was corresponding also to a hundred times smaller decrease in weight.
Plates of iron-chromium alloys containing 10% chromium were exposed on surfaces of 20 mm2 to tap water. The sample, which was exposed to a treatment according to the invention comprising heating at 480 C for 4 hours at the total pressure 2,0 x 10 5 mm ~g, showed after 36 hours exposure - ~ corrosion current, which was two hundred times lower than that of untreated samples after the same exposure time.
III
Plates of lron-chromium a1loys containing 17~ chromium were exposed A on surfaces of 20 mm to a 1~ NaCl solution in the presence of a gap.
The sample~ which was exposed to a treatment according to the invention comprising heating at 475C for 6 hours at the total pressure 1,8 x 10 5 mm Hg showed after 11 hours exposure one single pitting, while untreated samples after the same exposure time showed pitting over the entire gap area.
In the above examples and ther experimental correspondences is shown, that a preferred treatment consists of exposing the article to an oxygen containing gaseous atmosphere with a vacuum of about 3 . 10 5 - 10 5 mm Hg at a temperature of about ~00C for a period of about 4-6 hours.
~1Z79~V
IV
Plates of three different commercially available stainless steels were exposed on surfaces of 20 mm at room temperature to a 3% NaCl solution in the presence of a gap. The samples, which were subjected to a treat-ment according to the invention comprising a heating at 475 C for 1 hour at the total pressure 1,5 x 10 5 mm Hg showed after 24 hours exposure corrosion currents, which for all stainless steels were significantly lower than for untreated stainless steels after the same exposure time.
The differences in corrosion current for treated ~nd, respectively, untreated samples are apparent from Fig, 1, which is the result of the exposure during the first fifteen minutes in 3% NaCl solution and compositions according to the below Table 1 of the stainless steels included in the comparison. It should be added that the corrosion curr-ents during extended exposure tests continue to decrease with the time, but that the mutual order between different treated and untreated stainless steels is the same as after 15 minutes exposure~
The surface6 of iron-chromium alloys prior to heating in easeous atmos-phere can be subjected to some kind of treatment, such as mechanic polishin~, bright annealing, pickling, electrolyte polishing or etching, or alternatively they may not be treated. In all cases, however, a very increased corrosion resistance of a material treated accordine to the inYention is obtained.
~elow examples are gi~en which refer to bright annealed and, respect-ively, pickled ~aterial, while the above examples referred to mechanic-ally ground surfaces.
Brigh~ annealed plates of stainless steel SIS 2343 (as regards composit-~127940 ion see designation B in Table 1) were exposed on surfaces of 20 mm at room temperature to 3% neutral NaCl solution in the presence of a gap and during a simultaneous potentio-dynamic load, which in fiteps was increased by 50 mV per minute. The potential, at which local attacks were initiated adjacent the gap,i6 hereinafter called crevice corrosion potential. The samples, which were exposed to a treatment according to the invention comprising heating at 475 C for 2 hours at a total pressure ~f 5 x 10 5 mm Hg showed a crevice corrosion potential, which on the average was 550 mV hiBher than for corresponding untreated bright annealed steel samples.
VI
Pickled ~lates of stainless steel SIS 2333 (as regards composition, see designation D in Table I) were subjected to a similar corrosion test as de~cribed in Example V. The fiarnples, which were subjected to a treatment according to the invention comprising heating at 475 C
for 2 hour6 at the total pressure of 7 x 10 ~ mm Hg, showed a crevice corrosion potential, which on the average was 130 mm hi~her than for corresponding untreate~ pickled teel samples.
Tabele I. Chemical analysis in % by wei~ht Design- Material C Si Mr. CrNi r~0 Other ation A Cr18Mo2Ti 0,030 0~34 o~48 18.4 0.27 2.27 0.60 Ti B SIS 2343 o.o46 o.38 1 r30 17,7 11.0 2.74 C Cr18Ni25~oCu 0.020 o-s6 1.82 19.6 24.5 4.4 1.43 cu D SI5 2333 0.040 0~47 1.67 18.8 9.1 o ~
1~'~79~
_9_ The present invention can be applied to alloys other than pure iron and chromium alloys. As iron-chromium alloys according to the present invention are understood alloys, which in addition to the basic elements iron and chromium contain one or more of the basic elements nickel, aluminium, silicon, titanium, manganese, copper or molybdenum.
Method of making surface layers with improved corrosion properties on articles of iron-chromium alloys, and a surface layer made by the method -This invention relates to a method of improving the corrosion propert-ies of chromium-alloyed steels.
The alloying of, for example, chromium, molybdenum, silicon or aluminium into steel in order to improve the corrosion properties of the steel involves substantial manufacturing C08t8- The corrosion properties of a steel being determined by the condition of the steel surface, it is of interest to enrich the steel surface in respect of certain alloy-ing components, which have a positive effect or the corrosion resist-ance of the steel. In this way, either the amount of alloying compon-ents in the steel matrix could be decreased in order to achieve a cert-ain corrosion resistance, or the corrosion resistance for a given composition in the steel matrix could be increased.
For obtaining a surface layer on a substrate where the structure and composition in the surface layer differs from the substrate, one can choose between a number of known methods, for example metallization, electrolytic precipitat~on or cladding. The principle here is to apply the desired surface layer externally to the substrate ~ia, for example, '` . ' 1~Z7940 adsorption, condensation or precipitation on the surface of the substrate from a gaseous or liquid phase.
According to the present invention a surface layer with substantially improved corrosion properties is obtained thereby that, distinguished from the methods mentioned above, an oxide is formed on the surface of the substrate where the oxidized material is comprised in the substrate.
The present invention, thus, relates to a method of making a surface layer with impro~ed corrosion properties on articles of iron-chromium alloys where the article i8 heated in an oxygen containing atmosphere with vacuum.
The invention is characterized in that the article is heated in an oxygen containing gaseous atmosphere with a total vacuum of about 10 1 down to 10 8 mm Hg, preferably about 10 5 mm Hg, to a temperature, at which diffusion of the most reactive slloying component or compon-ents, primarily chromium, with respect to its tendency of combining with oxyeen, to the surface becomes perceptible, and at which temper-ature the remaining properties of the alloy substantially are maint-ained, and that the described condition for the article is maintained until a surface layer containing oxidized chromium has grown to a thickness of preferably 10 9 - 1a 7 m,whereby the resulting surface layer with respect to structure and composition transforms by degrees from a condition on the surface to a condition in the matrix of the metal alloy.
This invention, thus, distinguished from conventional methods where in all cases a surface layer is applied externally to a su~strate, relates to a method, at which the surface layer is made by means of alloying components comprised in the substrate. The surface layer thereby is 1~Z7940 formed by heating the substrate, which is a chromium steel, in a gaseous atmosphere at vacuum containing a low and well-controlled oxygen content.
At heating in gaseous atmosphere with vacuum, a preferential enrich-ment to the surface of the chromium steel takes place of that alloying component or those alloying components, which have the strongest tendency of forming compounds with oxygen present on the fiurface of the chromium steel. The term oxygen present on the steel surface also includes the oxygen compr-sed in the very thin oxide film, which usually exists on the chromium steel surface prior to the heating in the gaseous atmosphere, and the small but very well controlled amount of oxygen, which exists in the gaseous atmosphere and reaches to the surface of the article.
The temperature, to which the article is heated, is chosen so that diffusion of the most reactive alloying component or components to the surface becomes perceptible. For iron-chromium alloys the diffusion takes place above a temperature of about 300C. The temperature also must be chosen so that other properties characteristic of the metal alloy are not deteriorated. This temperature is for iron-chromium alloys below about 600 C, because above said temperature carbide is precipitated in the grain boundaries, and in certain cases pha6e transformations can occur. The stated lower as well as the stated higher temperature, of course, are individual for each type of iron-chromium alloy, but a suitable heating temperature for the majority of iron-chromium alloys is between 300C and 600C. A preferred temper-ature is about ~00 C. Surface layers, thus,with improved corrosion properties have been observed after heating in gaseous atmosphere in the range 300C-550C, with optimum results about 475C.
~12794~
The amount of oxygen being present on the surface of the article is to be adjusted both to the heating temperature and to the desired properties of the surface layer. In many applications the oxygen amount level should be so low that substantially only one of the alloying components of the arti-cle is capable to react with oxygen For effecting such a low supply of oxygen to the article surface, normally vacuum conditions are required, which depending on metal alloy and surface layer can extend from tenths of millimeters Hg to ultra-high vacuum conditions (~10 8 mm Hg). The heating can incertain cases also be carried out in protective atmosphere, but then the difficulties of maintaining a sufficiently low and well-controlled oxygen level are more obvious.
For obtaining a good result, said pressure range implies a total vacuum of about 10 - 10 mm Hg A preferred pressure is about 10 mm Hg. According to the invention, the article is to be treated at said pressure and temperature until a sur-face layer containing oxidized chromium has grown to a thickness of about 10 - 10 m and preferably 10 - 10 m, which, thus, is an extremely thin surface layer. The time of such a treatment amounts to a number of hours, as is exemplified in greater detail below.
The time of heat treatment, exclusive of heating and cooling periods, is to be adjusted, of course, to the amount of oxygen in the gaseous atmosphere and to the heating temperature. It was found that this implies heating times in the range one half to ten hours, with optimum results at about three hours~
The surface layer thus obtained, with a thickness varying be-tween 10 and 10 7 m, shows a structure and a composition which by degrees transforms from a condition in the outermost atom layer of the surface layer ~Z7940 to a condition characterizing the matrix of the metal alloy.
The improved corrosion properties are attributed to an obser~ed enrich-ment of alloying comp~nents, sùch as chromium, molybdenum or titanium in the surface layers thus formed.
As a consequence of the gradual transformation from substrate to sur-face layer, the surface layer i6 characterized by good adherence to the substrate. The transformation further takes place without great accumulations of defects or other material deficiencies. A further consequence of the fact that the surface layer is applied to the sub-strate internally and under vacuum conditions, is that the coat is the ~ame all over the article surface, thufi also in inward bulges and other surface areas where an external application would be rendered difficult by shading effects.
A surface layer made according to the present-method on articles of iron-chromium alloys, which were heated in an oxygen containing gaseous atmosphere under low pressure, thu6, comprises chromium of a higher concentration than the article in general, which chromium is oxidized entirely or partially, and which surface layer has a thickness of about 10-1 _ 10-6 m, preferably 10 9 - 10 m.
Examples:
I
a) A plate of iron-chromium alloy containing 5% chromium was exposed on a ~urface of 20 mm to tap water for 2 hours. After 2 hours a corrcsion current of 10 5 A was obtained.
b) A plate similar to that in a) was exposed according to the invention to a treatment consisting of heating at 475C for 6 hours at the total pressure 1,8 x 10 5 mm Hg. The resulting surface layer was characterized ~127940 by a gradual transformation from a high chromium content farthest outwardly in the surface layer to the low chromium content in the matrix of the alloy. When 20 mm2 of this treated surface were exposed to tap water, after 2 hours a corrosion current of 10 7 A was obtained.
The one hundred times lower corrosion current was corresponding also to a hundred times smaller decrease in weight.
Plates of iron-chromium alloys containing 10% chromium were exposed on surfaces of 20 mm2 to tap water. The sample, which was exposed to a treatment according to the invention comprising heating at 480 C for 4 hours at the total pressure 2,0 x 10 5 mm ~g, showed after 36 hours exposure - ~ corrosion current, which was two hundred times lower than that of untreated samples after the same exposure time.
III
Plates of lron-chromium a1loys containing 17~ chromium were exposed A on surfaces of 20 mm to a 1~ NaCl solution in the presence of a gap.
The sample~ which was exposed to a treatment according to the invention comprising heating at 475C for 6 hours at the total pressure 1,8 x 10 5 mm Hg showed after 11 hours exposure one single pitting, while untreated samples after the same exposure time showed pitting over the entire gap area.
In the above examples and ther experimental correspondences is shown, that a preferred treatment consists of exposing the article to an oxygen containing gaseous atmosphere with a vacuum of about 3 . 10 5 - 10 5 mm Hg at a temperature of about ~00C for a period of about 4-6 hours.
~1Z79~V
IV
Plates of three different commercially available stainless steels were exposed on surfaces of 20 mm at room temperature to a 3% NaCl solution in the presence of a gap. The samples, which were subjected to a treat-ment according to the invention comprising a heating at 475 C for 1 hour at the total pressure 1,5 x 10 5 mm Hg showed after 24 hours exposure corrosion currents, which for all stainless steels were significantly lower than for untreated stainless steels after the same exposure time.
The differences in corrosion current for treated ~nd, respectively, untreated samples are apparent from Fig, 1, which is the result of the exposure during the first fifteen minutes in 3% NaCl solution and compositions according to the below Table 1 of the stainless steels included in the comparison. It should be added that the corrosion curr-ents during extended exposure tests continue to decrease with the time, but that the mutual order between different treated and untreated stainless steels is the same as after 15 minutes exposure~
The surface6 of iron-chromium alloys prior to heating in easeous atmos-phere can be subjected to some kind of treatment, such as mechanic polishin~, bright annealing, pickling, electrolyte polishing or etching, or alternatively they may not be treated. In all cases, however, a very increased corrosion resistance of a material treated accordine to the inYention is obtained.
~elow examples are gi~en which refer to bright annealed and, respect-ively, pickled ~aterial, while the above examples referred to mechanic-ally ground surfaces.
Brigh~ annealed plates of stainless steel SIS 2343 (as regards composit-~127940 ion see designation B in Table 1) were exposed on surfaces of 20 mm at room temperature to 3% neutral NaCl solution in the presence of a gap and during a simultaneous potentio-dynamic load, which in fiteps was increased by 50 mV per minute. The potential, at which local attacks were initiated adjacent the gap,i6 hereinafter called crevice corrosion potential. The samples, which were exposed to a treatment according to the invention comprising heating at 475 C for 2 hours at a total pressure ~f 5 x 10 5 mm Hg showed a crevice corrosion potential, which on the average was 550 mV hiBher than for corresponding untreated bright annealed steel samples.
VI
Pickled ~lates of stainless steel SIS 2333 (as regards composition, see designation D in Table I) were subjected to a similar corrosion test as de~cribed in Example V. The fiarnples, which were subjected to a treatment according to the invention comprising heating at 475 C
for 2 hour6 at the total pressure of 7 x 10 ~ mm Hg, showed a crevice corrosion potential, which on the average was 130 mm hi~her than for corresponding untreate~ pickled teel samples.
Tabele I. Chemical analysis in % by wei~ht Design- Material C Si Mr. CrNi r~0 Other ation A Cr18Mo2Ti 0,030 0~34 o~48 18.4 0.27 2.27 0.60 Ti B SIS 2343 o.o46 o.38 1 r30 17,7 11.0 2.74 C Cr18Ni25~oCu 0.020 o-s6 1.82 19.6 24.5 4.4 1.43 cu D SI5 2333 0.040 0~47 1.67 18.8 9.1 o ~
1~'~79~
_9_ The present invention can be applied to alloys other than pure iron and chromium alloys. As iron-chromium alloys according to the present invention are understood alloys, which in addition to the basic elements iron and chromium contain one or more of the basic elements nickel, aluminium, silicon, titanium, manganese, copper or molybdenum.
Claims (6)
1. A method of making surface layers with improved corrosion properties on articles of iron-chromium alloys, where the article is heated in an oxygen containing atmosphere with vacuum, comprising heating the article in an oxygen containing gaseous atmosphere with a total vacuum in the range of about 10-1 down to 10-8 mm Hg, to a temperature, at which diffusion of the most reactive alloy component or components, primarily chromium, with respect to the tendency of combining with oxygen, to the surface becomes perceptible, and at which temperature the remaining properties of the alloy substantially are main-tained, and that the described condition of the article is main-tained until a surface layer containing oxidized chromium has grown to a thickness in the range of about 10-10 to 10-6 m, whereby the resulting surface layer with respect to structure and composition by degrees transforms from a condition on the surface to a condition in the matrix of the metal alloy.
2. The method according to claim 1 wherein the article is heated in an oxygen containing gaseous atmosphere with a total vacuum of about 10-5 mm Hg.
3. The method according to claim 1 wherein the sur-face layer containing oxidized chromium has grown to a thick-ness in the range of about 10-9 to 10-7 m.
4. The method according to any of claims 1, 2 or 3 wherein the alloy is exposed to an oxygen containing gaseous atmosphere with a vacuum of about 3 . 10-5 - 10-5 mm Hg at a temperature of about 500°C for a time of about 4-6 hours.
5. A surface layer with improved corrosion properties on articles of iron-chromium alloys made by heating the article in an oxygen containing gaseous atmosphere under low pressure, wherein the surface layer comprises chromium of a higher concentration than the article in general, which chromium is oxidized entirely or partially, and the thickness of the surface layer is in the range of about 10-10 to 10-6 m.
6. The surface layer according to claim 5 wherein the thickness is in the range of about 10-9 to 10-7 m.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7708604-9 | 1977-07-27 | ||
| SE7708604A SE407081B (en) | 1977-07-27 | 1977-07-27 | METHODS TO PROVIDE SURFACES WITH IMPROVED CORROSION PROPERTIES FOR FORMAL OF IRON CHROME OILS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1127940A true CA1127940A (en) | 1982-07-20 |
Family
ID=20331915
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA307,885A Expired CA1127940A (en) | 1977-07-27 | 1978-07-21 | Method of making surface layers with improved corrosion properties on articles of iron-chromium alloys, and a surface layer made by the method |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5452636A (en) |
| AU (1) | AU3842478A (en) |
| CA (1) | CA1127940A (en) |
| DE (1) | DE2832836A1 (en) |
| FR (1) | FR2398812A1 (en) |
| GB (1) | GB2001677B (en) |
| IT (1) | IT1105925B (en) |
| SE (1) | SE407081B (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3108160C2 (en) * | 1981-02-06 | 1984-12-06 | M.A.N. Maschinenfabrik Augsburg-Nürnberg AG, 8000 München | Process for the production of oxide layers on chrome and / or nickel alloy steels |
| DE3215314C2 (en) * | 1982-04-23 | 1984-12-06 | M.A.N. Maschinenfabrik Augsburg-Nürnberg AG, 8000 München | Process for the production of oxide layers on a titanium-based alloy surface |
| GB2130253B (en) * | 1982-10-05 | 1985-10-16 | Smiths Industries Plc | Reducing adherence of solder to gripping tools |
| DE3338852A1 (en) * | 1982-12-11 | 1984-06-14 | Maschf Augsburg Nuernberg Ag | METHOD AND DEVICE FOR COATING WORKPIECES BY MEANS OF CHEMICAL, HETEROGENIC GAS PHASE REACTION |
| CH671407A5 (en) * | 1986-06-13 | 1989-08-31 | Balzers Hochvakuum | |
| JP2976333B2 (en) * | 1987-10-24 | 1999-11-10 | 忠弘 大見 | Stainless steel, its manufacturing method and pressure reducing device |
| JP2976301B2 (en) * | 1987-10-24 | 1999-11-10 | 忠弘 大見 | Stainless steel, its manufacturing method and pressure reducing device |
| JPH01198463A (en) * | 1988-02-04 | 1989-08-10 | Tadahiro Omi | Stainless steel member for semiconductor-manufacturing equipment and its production |
| JP2768952B2 (en) * | 1988-08-04 | 1998-06-25 | 忠弘 大見 | Metal oxidation treatment apparatus and metal oxidation treatment method |
| GB2234530A (en) * | 1989-06-30 | 1991-02-06 | Shell Int Research | Heat treatment of high temperature steels |
| JPH0559524A (en) * | 1990-08-31 | 1993-03-09 | Nkk Corp | Stainless steel member for ultrahigh vacuum equipment and its production |
| WO1993010274A1 (en) * | 1991-11-20 | 1993-05-27 | Tadahiro Ohmi | Method of forming passive oxide film based on chromium oxide and stainless steel |
| JP2737551B2 (en) * | 1992-07-14 | 1998-04-08 | 住友金属工業株式会社 | Manufacturing method of austenitic stainless steel for high purity gas with excellent corrosion resistance |
| JP3027279B2 (en) * | 1993-03-25 | 2000-03-27 | 日本碍子株式会社 | Method for improving oxidation resistance of Fe-Cr-Al alloy |
| DE4432013A1 (en) * | 1993-12-17 | 1995-06-22 | Kobe Steel Ltd | Surface treatment of metallic material to impart improved corrosion resistance |
| DE102004010689B3 (en) | 2004-02-27 | 2005-06-30 | Schott Ag | Absorber with radiation-selective absorber coating for use of thermic solar energy has oxide diffusion blocking layer provided by oxidized components of metal substrate |
| JP2010070828A (en) * | 2008-09-22 | 2010-04-02 | Fujifilm Corp | Mask fixture for vacuum film deposition and method for producing the same |
| JP2010070830A (en) * | 2008-09-22 | 2010-04-02 | Fujifilm Corp | Fixture for evaporation source and method for producing the same |
| JP2010070829A (en) * | 2008-09-22 | 2010-04-02 | Fujifilm Corp | Fixture for evaporation source and method for producing the same |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL62256C (en) * | 1943-11-11 | 1948-01-15 | ||
| FR1226734A (en) * | 1958-03-12 | 1960-07-15 | Process for the production of oxide layers on iron and iron alloy articles | |
| US3185597A (en) * | 1963-02-15 | 1965-05-25 | Sylvania Electric Prod | Metal oxidizing process |
| US3345218A (en) * | 1964-04-02 | 1967-10-03 | Owens Illinois Inc | Preoxidation of stainless steel for glass-to-metal sealing |
-
1977
- 1977-07-27 SE SE7708604A patent/SE407081B/en unknown
-
1978
- 1978-07-20 GB GB787830471A patent/GB2001677B/en not_active Expired
- 1978-07-21 CA CA307,885A patent/CA1127940A/en not_active Expired
- 1978-07-26 DE DE19782832836 patent/DE2832836A1/en not_active Ceased
- 1978-07-27 AU AU38424/78A patent/AU3842478A/en active Pending
- 1978-07-27 FR FR7822308A patent/FR2398812A1/en active Granted
- 1978-07-27 JP JP9100878A patent/JPS5452636A/en active Pending
- 1978-07-27 IT IT50493/78A patent/IT1105925B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| FR2398812B1 (en) | 1983-08-12 |
| AU3842478A (en) | 1980-01-31 |
| DE2832836A1 (en) | 1979-02-15 |
| SE7708604L (en) | 1979-01-28 |
| IT1105925B (en) | 1985-11-11 |
| IT7850493A0 (en) | 1978-07-27 |
| GB2001677B (en) | 1982-09-02 |
| FR2398812A1 (en) | 1979-02-23 |
| SE407081B (en) | 1979-03-12 |
| GB2001677A (en) | 1979-02-07 |
| JPS5452636A (en) | 1979-04-25 |
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