EP0420939B1 - Apparatus for and method of chromizing articles - Google Patents

Apparatus for and method of chromizing articles Download PDF

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Publication number
EP0420939B1
EP0420939B1 EP89908116A EP89908116A EP0420939B1 EP 0420939 B1 EP0420939 B1 EP 0420939B1 EP 89908116 A EP89908116 A EP 89908116A EP 89908116 A EP89908116 A EP 89908116A EP 0420939 B1 EP0420939 B1 EP 0420939B1
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EP
European Patent Office
Prior art keywords
retort
furnace
articles
set forth
fluid medium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP89908116A
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German (de)
English (en)
French (fr)
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EP0420939A1 (en
Inventor
Everett C. Lewis
Harley A. Grant
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Combustion Engineering Inc
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Combustion Engineering Inc
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Publication of EP0420939A1 publication Critical patent/EP0420939A1/en
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    • 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
    • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
    • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
    • 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
    • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
    • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
    • C23C10/34—Embedding in a powder mixture, i.e. pack cementation
    • C23C10/36—Embedding in a powder mixture, i.e. pack cementation only one element being diffused
    • C23C10/38—Chromising
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H51/00—Forwarding filamentary material
    • B65H51/005—Separating a bundle of forwarding filamentary materials into a plurality of groups
    • B65H51/01—Separating a bundle of forwarding filamentary materials into a plurality of groups by means of static electricity
    • 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
    • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
    • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
    • C23C10/30—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes using a layer of powder or paste on the surface
    • C23C10/32—Chromising
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2701/00—Handled material; Storage means
    • B65H2701/30—Handled filamentary material
    • B65H2701/31—Textiles threads or artificial strands of filaments

Definitions

  • This invention relates to the coating of articles, and more specifically to an apparatus for and a method of applying a chromized coating to one or more of the surfaces of an article as a means of providing protection thereto particularly with respect to corrosion.
  • chromizing has come to mean a high temperature diffusion process in which the treated surface or surfaces of a steel object are alloyed with chromium. Briefly stated, in accord with this process the steel object is submerged in a retort in powder that contains chromium, the retort is sealed and is then heated along with its contents in a furnace for several hours at an elevated temperature. This heating causes the chromium in the powder to gasify, to deposit on the steel object, and to diffuse into the base metal of the steel object to a depth and in a concentration that is dependent upon numerous metallurgical and process variables.
  • Chemical recovery boilers are an example of one such boiler related application.
  • a chemical recovery boiler essentially is an apparatus for recovering and processing certain chemicals which are used in a pulp mill.
  • black liquor i.e., the spent cooling liquid that is generated during pulp making. It is this black liquor which is burned as fuel in the chemical recovery boiler.
  • the black liquor was burned in the chemical recovery boiler as a means of recovering chemicals before use was also made thereof to generate steam.
  • the value of the chemicals that are recovered through the use of the chemical recovery boiler is normally on the order of three times greater than that of the steam generated by the chemical recovery boiler.
  • the steam generated by the chemical recovery boiler is a substantial amount i.e., perhaps half, of the steam that a pulp mill requires.
  • the black liquor which is burned as fuel in the chemical recovery boiler produces an environment which has proven to be highly corrosive to the carbon steel waterwalls of the chemical recovery boiler.
  • the boiler tubes which are employed in the waterwall panels of the chemical recovery units heretofore have either had to be replaced frequently and/or metallized, both necessitating a shutting down of the chemical recovery boiler in order to provide access thereto.
  • Another option can be special composite tubes of carbon steel with an outside clad of Type 304 stainless steel but such tubes are relatively costly.
  • An alternative thereto would be to employ boiler tubes that have been chromized, i.e., boiler tubes that have had a chromium coating applied thereto.
  • chromized components i.e., components to which a chromium coating has been applied
  • resource recovery boilers Because of the ever diminishing number of landfills that remain available for receiving municipal waste, more and more communities are resorting to burning their municipal waste.
  • One means of accomplishing this burning of municipal waste that is being employed by such communities is through the use of a boiler of the type which is most frequently referred to by those in the industry as a resource recovery boiler.
  • Coal-fired utility boilers represent still another example of a boiler related application for which chromized components, i.e., components to which a chromium coating has been applied, appear to be particularly suited for use.
  • chromized components i.e., components to which a chromium coating has been applied
  • coal-fired utility boilers especially of the supercritical pressure type, have suffered general and/or localized attack of the waterwalls thereof.
  • metallizing has not proven to be effective in combating this very aggressive sulfidizing environment.
  • components which have had a chromium coating applied thereto are resistant, even when located in areas in which severe metal loss has previously been encountered, to such sulfidation attack and metal loss.
  • the superheater and the reheater sections thereof have been known to suffer from high temperature ash corrosion and oxidation.
  • This high temperature ash corrosion and oxidation in the superheater and reheater sections of such boilers can be addressed in some instances by upgrading the material from ferritic steel to austenitic stainless steel.
  • ferritic steel due to the differing coefficients of thermal expansion of ferritic and austenitic stainless steel, there are other instances wherein it is desirable, or even necessary, to continue to utilize a ferritic steel as the material from which some or all of the components in the superheater section and/or the reheater section of the boiler are fabricated.
  • the steam side oxidation product that forms on the tubes in the superheater section and the reheater section of the boiler which are touched by gas is known to have a potential for producing significantly increasing metal temperatures.
  • the oxide scale that forms on surfaces to which a chromium coating has been applied have been found to be extremely thin. Consequently, because the oxide scale is extremely thin, the metal temperature of boiler tubes fabricated from ferritic alloy material that have been chromized, i.e., have had a chromium coating applied thereto, will not increase significantly even when subjected to hours of operation.
  • boiler tubes that have the fire sides thereof, i.e., the sides thereof which are presented to the fire in the boiler, exposed to a high front to back temperature differential, e.g., usually those that are exposed to radiant heat, are sometimes found to have suffered circumferential cracking. While the cause of such circumferential cracking is not completely understood it is believed that it is induced by thermal strains, the mechanism by which the penetration of the base metal, i.e., the cracking thereof, occurs is as a consequence of the repeated cracking of the semi-protective oxidation product formed on the boiler tube surface.
  • the waterwall tubes of coal-fired utility boilers especially of the supercritical pressure type, that experience sulfidation wastage attack are known to also experience corrosion fatigue cracking particularly in those areas thereof which are outside of the regions wherein severe metal loss is experienced.
  • radiant wall tubes in the reheater section of coal-fired boilers have also experienced this type of cracking, i.e., thermally induced corrosion fatigue cracking.
  • chromizing such boiler tubes i.e., applying a chromium coating to the surface thereof, has shown itself to be quite resistant to the aforereferenced type of corrosion fatigue cracking, i.e., the thermally induced corrosion fatigue cracking which has been discussed above.
  • document US-A-2 836 513 discloses a method of chromizing ferrous metal articles comprising the steps of coating the articles with a watery dispersion of chromium, the complex fluoride of ammonium and chromium and an inert bodying agent to form an adhesive bonded chromizing layer on the ferrous metal articles; and heating the ferrous metal articles to a temperature of 1600 to 2200F.
  • an object of the present invention to provide a new and improved apparatus for applying a coating of chromium to one or more of the surfaces of an article as a means of protecting the latter.
  • a further object of the present invention is to provide such an apparatus and method for applying a coating of chromium to the surface of an article wherein the chromium coating that is applied in accord therewith is thicker than that which it has heretofore been possible to provide through the use of prior art chromium methods.
  • a still further object of the present invention is to provide such an apparatus and method for applying a coating of chromium to the surface of an article wherein the chromium coating that is applied in accord therewith contains a higher concentration of chromium than that which heretofore it has been possible to achieve through the use of prior art chromium coating methods.
  • Yet another object of the present invention is to provide such an apparatus and method for applying a coating of chromium to the surface of an article wherein the article to the surface of which in accord therewith the chromium coating is applied is larger in size than the size of the articles to which it has heretofore been possible to apply a chromium coating to the surface thereof through the use of prior art chromium coating methods.
  • Yet still another object of the present invention is to provide such an apparatus and method for applying a coating of chromium to the surface of an article which are relatively inexpensive to provide, which are relatively easy to employ and which are characterized in that the chromium coating provided thereby is better capable of resisting corrosion than the chromium coatings which heretofore have been available for use for the same purpose.
  • a new and improved apparatus for applying a chromium coating to one or more of the surfaces of an article particularly where the article is intended to be employed in an application wherein the article will be subjected to corrosion.
  • the subject apparatus includes a stationary foundation which is preferably formed of a cast refractory material. Supported on the stationary foundation in spaced relation thereto by means of a plurality of supports that are positioned on the stationary foundation in spaced relation one to another is a retort. Within the retort are placed the articles to which the chromium coating is to be applied.
  • the retort has suitably formed therein an inlet opening through which a fluid medium is supplied to the interior of the retort.
  • the retort has suitably formed therein an outlet opening through which the fluid medium that enters the retort through the aforementioned inlet opening exits from the retort after flowing therethrough.
  • the subject apparatus further includes a furnace suitably provided with heating means which is movable to and from a position such that when in the latter position the furnace is operative to effect by means of the heating means associated therewith the uniform heating of the retort for a preestablished period of time at a predetermined temperature.
  • the furnace has formed therein at one location thereof an inlet opening through which a fluid medium is supplied to the interior of the furnace, and at another location thereof the furnace has formed therein an outlet opening through which the fluid medium that enters the furnace through the inlet opening formed therein for this purpose exits from the furnace after flowing therethrough.
  • the subject apparatus includes seals suitably positioned in sealing relation between the furnace and the stationary foundation so as to be operative to seal off the furnace and thereby also the retort from the environment surrounding the furnace while the retort is being heated by the heating means with which the furnace is provided.
  • a new and improved method of applying a chromium coating to one or more of the surfaces of an article particularly where the article is intended to be employed in an application wherein the article will be subjected to corrosion includes the steps of providing a stationary foundation which is preferably formed of a cast refractory material, positioning a plurality of supports on the stationary foundation in spaced relation one to another, mounting a retort in supported relation on the supports, spreading a layer of a powder composed of a mix of ammonium chloride, alumina and ferrochromium over the bottom of the retort, positioning a layer of articles to which the chromium coating is to be applied on the layer of powder in the retort, covering the layer of articles with a layer of powder, alternately adding to the retort a layer of articles to which the chromium coating is to be applied and a layer of powder until the retort contains the desired number of articles, covering the
  • the apparatus 10 is designed to be operative for purposes of applying a chromium coating to one or more of the surfaces of an article, and especially an article that is intended to be employed in an application wherein the article will be subjected to corrosion.
  • the apparatus 10 includes a stationary foundation, the latter being generally designated by the reference numeral 12 in Figure 1.
  • the stationary foundation 12 preferably is formed of a cast refractory material.
  • the stationary foundation 12 is designed to serve a dual function. Namely, the stationary foundation 12 is intended to be in the nature of a support base for the apparatus 10.
  • the stationary foundation 12 is operative to provide a thermal insulation barrier between the apparatus 10 and the floor (not shown) of the facility whereat the apparatus 10 is located, e.g., the floor of an industrial-type facility.
  • the stationary foundation 12 has supported thereon in suitably spaced relation one to another a plurality of supports.
  • each of the plurality of supports is denoted in Figure 1 by the same reference numeral, i.e., the reference numeral 14.
  • the plurality of supports 14 are preferably each formed of a cast refractory material.
  • the plurality of supports 14 are also designed to be operative to function as both a support surface and a thermal insulation barrier.
  • the support surface which the plurality of supports 14 provides is for the retort that is generally designated in Figures 1, 2 and 3 of the drawing by the reference numeral 16. It is within the retort 16 that the articles are placed which are to have a chromium coating applied to one or more surfaces thereof.
  • the method by which the articles that are placed within the retort 16 have a chromium coating applied to one or more surfaces thereof forms another aspect of the present invention. Reference will be had herein in greater detail subsequently to this method.
  • the retort 16 is designed to function as the enclosure within which the articles that are to have a chromium coating applied to one or more surfaces thereof are place while these articles in a manner yet to be described herein are being uniformly heated for a preestablished period of time to a predetermined temperature for purposes of effecting the application of the chromium coating thereto.
  • the retort 16 in accordance with the best mode embodiment of the invention is preferably formed of any suitable conventional type of material which embodies sufficient strength so as to be capable of supporting therewithin a multiplicity of relatively large objects, e.g., a multiplicity of relative long, tubular metallic articles, while these objects are being heated to a temperature of on the order of 2100°F (1149°C).
  • the retort 16 in accord with the best mode embodiment of the invention preferably takes the form of a rectangular structure defined by a base, identified in the drawing by the reference numeral 18 having four upstanding side walls, each denoted by the same reference numeral 20 in the drawing, connected thereto by means of any conventional connection means (not shown) suitable for use for such a purpose so as to thereby collectively form a closed box-like structure.
  • the retort 16 includes a cover, identified by the reference numeral 22 in the drawing, which is designed to be removably secured to the top of the box-like structure formed by the base 18 and the upstanding side walls 20 connected thereto, so as to enable access to be had to the interior of the retort 16 for purposes of positioning therewithin the articles to which a chromium coating is to be applied to one or more surfaces thereof, and for thereafter removing these articles from the interior of the retort 16 once the chromium coating has been applied to the one or more surfaces of the articles.
  • the latter is designed to be sealed in place on the box-like structure formed by the base 18 and the upstanding side walls 20 once the articles to which the chromium is to be applied to one or more surfaces thereof have been emplaced within the latter while these articles are being heated to effectuate, in a manner yet to be described, the application of the chromium coating to one or more surfaces thereof.
  • the retort 16 is provided at a first location with inlet passage means, the latter being schematically illustrated in Figure 2 of the drawing wherein the inlet passage means is generally designated by the reference numeral 24.
  • the inlet passage means 24 is suitably formed in the retort 16 at a first location thereof such as to be operative for the purpose of enabling an inert fluid medium to be supplied therethrough to the interior of the retort 16.
  • the retort 16 likewise for a purpose to be described in more detail hereinafter is also provided at another location thereof with outlet passage means, schematically illustrated in Figure 2 of the drawing wherein the outlet passage means is generally designated by the reference numeral 26.
  • the outlet passage means 26 is suitably formed in the retort 16 so as to be operative for the purpose of enabling the inert fluid medium, which is supplied to the interior of the retort 16 through the inlet passage means 24, to exit through the outlet passage means 26 after having flowed through the retort 16.
  • both the inlet passage means 24 and the outlet passage means 26 may embody any suitable conventional form of construction such that the inlet passage means 24 and the outlet passage means 26 are each capable of functioning in the manner desired thereof, i.e., as has been described hereinbefore.
  • the apparatus 10 further includes a furnace generally designated in the drawing by the reference numeral 28.
  • the furnace 28 preferably is substantially rectangular in configuration.
  • the furnace 28 is constructed so as to embody a configuration which is complementary to the configuration of the retort 16, but which in size, i.e., in terms of the dimensions thereof, is larger than that of the retort 16 such that the furnace 28 is movable between a first position wherein the furnace 28 is located in surrounding relation to the retort 16 in the manner depicted in Figure 1 of the drawing and a second position (not shown) wherein the furnace 28 is located in nonsurrounding relation to the retort 16.
  • the furnace 28 is suitably provided with grasping means.
  • the grasping means employed take the form of a plurality of conventional lugs such as those denoted by the reference numeral 30 in Figure 1 of the drawing.
  • the lugs 30 are suitably secured in spaced relation to one another preferably on the top, seen at 32 in Figure 1, of the furnace 28 such as to project outwardly therefrom.
  • the lugs 30 are designed to be engaged by means of an industrial-type crane, or any other similar piece of equipment which is suitable for use for such a purpose, to effectuate the moving of the furnace 28 to and from surrounding relation relative to the retort 16.
  • any conventional form of grasping means suitable for use for the aforedescribed purpose may be employed in lieu of the lugs 30 without departing from the essence of the present invention.
  • the furnace 28 embodies heating means, the latter being denoted generally by the reference numeral 34 in Figure 1.
  • the heating means 34 in accord with the best mode embodiment of the invention consists of a multiplicity of electrical heating elements 36 suitably positioned in supported relation within the furnace 28 such that when the furnace 28 is positioned in surrounding relation to the retort 16 in the manner illustrated in Figure 1 of the drawing the multiplicity of electrical heating elements 36 are operative to effectuate the uniform heating to a predetermined temperature for a preestablished period of time of the retort 16 and thereby of also the contents of the retort 16, i.e., the articles which have been placed within the retort 16, for purposes of having a chromium coating applied to one or more surfaces thereof.
  • the predetermined temperature to which reference is being had herein is preferably a temperature of 2100°F. (1149°C), while the preestablished period of time to which reference is being had herein is preferably a period of ten hours.
  • the predetermined temperature to which reference is being had herein is preferably a temperature of 2100°F. (1149°C)
  • the preestablished period of time to which reference is being had herein is preferably a period of ten hours.
  • the furnace 28 as best understood with reference to Figure 1 of the drawing is, in a manner similar to that described hereinbefore in connection with the discussion of the nature of the construction of the retort 16, provided with inlet passage means, the latter being schematically illustrated in Figure 1 of the drawing wherein the inlet passage means is generally designated by the reference numeral 38.
  • the inlet passage means 38 is suitably formed in the furnace 28 at a first location thereof such as to be operative for the purpose of enabling a fluid medium to be supplied therethrough to the interior of the furnace 28.
  • the furnace 28 likewise for a purpose to be described in more detail hereinafter is also provided at another location thereof with outlet passage means, the latter being schematically illustrated in Figure 1 of the drawing wherein the outlet passage means is generally designated by the reference numeral 40.
  • the outlet passage means 40 is suitably formed in the furnace 29 so as to be operative for the purpose or enabling the fluid medium, which is supplied to the interior of the furnace 28 through the inlet passage means 38, to exit through the outlet passage means 40 after having flowed through the furnace 28.
  • both the inlet passage means 38 and the outlet passage means 40 may embody any suitable conventional form of construction which will enable the inlet passage means 38 and the outlet passage means 40 to function in the manner desired thereof, i.e., as has been described hereinbefore.
  • the multiplicity of electrical heating elements 36 of the heating means 34 which are supported within the furnace 28 are suitable enshrouded by conventional insulation means (not shown) such that the heat being generated by the multiplicity of electrical heating elements 36 does not escape to the exterior of the furnace 28 but rather does in fact accomplish the heating of the retort 16 and the articles emplaced therewithin to the extent required in order to successfully effectuate the application in the manner which has been described hereinbefore of a chromium coating to the articles that are in the retort 16. Any known conventional form of insulation means capable of performing in the aforedescribed manner may be selected for use for this purpose.
  • the apparatus 10 as best understood with reference to Figure 1 of the drawing includes sealing means, the latter being schematically illustrated in Figure 1 of the drawing wherein the sealing means is identified generally by the reference numeral 42.
  • the sealing means 42 as shown in Figure 1 of the drawing is designed so as to be capable of being interposed between the furnace 28 and the stationary foundation 12.
  • the sealing means 42 is designed to be operable to provide a seal between the furnace 28 and the stationary foundation 12 when the retort 16 is positioned in the manner depicted in Figure 1 of the drawing wherein the retort 16 is being supported on the stationary foundation 12 by virtue of being positioned on the plurality of supports 14 and the furnace 28 has been moved into surrounding relation relative to the retort 16 whereby the furnace 28 occupies the position relative to the retort 16 that is shown in Figure 1 of the drawing.
  • the sealing means 42 is intended to be operative to seal off the furnace 28 and thereby also the retort 16 from the environment surrounding the furnace 28 while the retort 16 as well as the articles emplaced therewithin are being heated to the desired temperature for the required period of time by the multiplicity of electrical heating elements 36 of the heating means 34 with which as has been described in detail hereinbefore the furnace 28 is suitably provided.
  • any known conventional form of sealing means capable of being employed in the aforedescribed manner, e.g., having the strength to resist the weight applied thereto by the furnace 28 and to resist the high temperatures to which the sealing means 42 will be subjected for a prolonged period of time, may be utilized as the sealing means 42 in the apparatus 10.
  • the sealing means 42 may be suitably mounted on the furnace 28 so as to be movable therewith into and out of sealing engagement with the stationary foundation 12.
  • a method of applying a chromium coating to one or more of the surfaces of an article wherein the subject method consists of the steps which are described hereinafter.
  • the subject method consists of the steps which are described hereinafter.
  • a stationary foundation which may, for example, take the form of the stationary foundation 12 that is depicted in Figure 1 of the drawing.
  • This stationary foundation in accord with the best mode embodiment of the invention preferably is made of a suitable conventional form of cast refractory material.
  • a plurality of supports such as, for instance, the supports 14 shown in Figure 1 of the drawing are positioned on the stationary foundation in suitably spaced relation one to another.
  • a retort having a cover and which in accord with the best mode embodiment of the invention, preferably embodies a construction such as that of the retort 16 depicted in Figures 1, 2 and 3 of the drawing is positioned, absent the cover thereof, in suitably supported relation on the plurality of supports to which hereinbefore reference has been had.
  • this powder preferably is composed of a mix of ammonium chloride, alumina and ferrochromium.
  • a layer of articles which may, for example, be in the form of a plurality of the articles, i.e., a plurality of the pairs of joined tubular members, which are depicted in Figure 4 of the drawing, or which may be in the form of a plurality of the article, i.e., a plurality of the single tubular member, which is depicted in Figure 5 of the drawing, or which may be in the form of a plurality of the article, i.e., a plurality of the non-tubular member, which is depicted in Figure 6 of the drawing is placed in the retort on top of the aforedescribed layer of powder which has been spread over the bottom of the retort.
  • this layer of articles which has been emplaced within the retort is covered with a layer of powder consisting of the same mix, i.e., ammonium chloride, alumina and ferrochromium, as that of the layer of powder which in the manner described hereinbefore has been spread over the bottom of the retort.
  • a layer of powder consisting of the same mix, i.e., ammonium chloride, alumina and ferrochromium
  • a layer of articles and a layer of powder of the same mix as that which has been described hereinabove are alternately added to the retort until the retort's capacity to receive articles is reached, or until the desired number of articles have been emplaced in the retort if this number of articles is less than the number of articles that is required to reach the retort's capacity to receive articles therewithin.
  • the uppermost layer, i.e., the last layer of articles is then covered with a layer of powder of the same mix as that described herein previously. In accord with the best mode embodiment of the invention this layer of powder is of a predetermined thickness.
  • the cover, i.e., the lid, of the retort is suitably positioned on the retort so as to close off access to the interior thereof, and is then sealed in place through the use of any conventional form of sealing means suitable for use for such a purpose as, for example, welding, that is by welding the cover in place on the retort.
  • a furnace containing heating means is positioned in surrounding relation to the retort.
  • the furnace is designed so as to be movable into and out of surrounding relation relative to the retort.
  • this furnace preferably embodies a construction such as that of the furnace 28 which is illustrated in Figure 1 of the drawing.
  • the furnace 28 is the furnace of which use is made in the course of practicing the subject method in accord with this aspect of the present invention or not, it is essential to the successful practice of the subject method that the furnace which is employed in this connection be capable of heating to a predetermined temperature for a preestablished period of time articles which are relatively large in size such that each article is heated throughout uniformly to this predetermined temperature and once having been heated uniformly to this predetermined temperature the article is capable of being maintained continuously at this uniform predetermined temperature throughout for a preestablished period of time, i.e., for a relatively prolonged period of time, e.g., on the order of upwards of ten hours.
  • this sealing off of the furnace and of the retort is preferably accomplished through the use of sealing means such as the sealing means identified in Figure 1 of the drawing by the reference numeral 42.
  • the heating of the articles that are emplaced within the retort to a predetermined temperature for a preestablished period of time is commenced.
  • This heating of the articles is accomplished by means of the heating means with which the furnace is suitably provided for this purpose.
  • a fluid medium is being supplied to the interior of the retort through conventionally constructed inlet passage means with which the retort is suitably provided for this purpose.
  • This fluid medium is designed to be operative to effect a purging of air from the interior of the retort.
  • the fluid medium that is supplied thereto exits from the retort through conventionally constructed outlet passage means with which the retort is suitably provided for this purpose.
  • a fluid medium is also simultaneously being supplied to the interior of the furnace, i.e., in surrounding relation to the retort, through conventionally constructed inlet passage means with which the furnace is suitably provided for this purpose.
  • the fluid medium supplied to the interior of the furnace i.e., in surrounding relation to the retort, is like the fluid medium supplied to the interior of the retort designed to be operative to perform a purging function.
  • the fluid medium supplied to the interior of the furnace i.e., in surrounding relation to the retort, is designed to be operative to purge the air from the area to which the fluid medium is supplied. After flowing through the interior of the furnace the fluid medium that is supplied thereto exits from the furnace through outlet passage means with which the furnace is suitably provided for this purpose.
  • the heating of the articles emplaced in the retort by the heating means with which the furnace is provided for this purpose continues until such time as the articles that are emplaced within the retort are heated uniformly throughout to a first predetermined temperature whereupon these articles are continuously maintained uniformly throughout at this first predetermined temperature for a preestablished period of time.
  • the heating means with which the furnace is provided is shut off, and the retort and thereby also the articles emplaced in the retort are permitted to cool down. This cooling down of the articles emplaced in the retort continues until these articles have cooled down uniformly throughout to a second predetermined temperature.
  • the furnace is then removed from in surrounding relation relative to the retort.
  • the cover is removed from the retort. With the cover of the retort removed, the residue of the powder mix and the articles emplaced within the retort to which a chromium coating has now been applied to one or more surfaces thereof are removed from the interior of the retort. Thereafter, the residual powder still on the surfaces of the articles is cleaned therefrom. Once the articles have been cleaned of residual powder, the articles then may be subjected to heat treatment and/or any other form of manufacturing process steps to which it may be deemed desirable to subject the articles.
  • the article to which a chromium coating is to be applied to one or more surfaces thereof shall be the tubular member which is illustrated in Figure 5 of the drawing wherein the tubular member is generally designated by the reference numeral 44.
  • the surface of the tubular member 44 to which the chromium coating will be applied shall be the outer circumference thereof whereby the tubular member 44 is provided with a chromium coating in the manner that is depicted in Figure 5 of the drawing wherein the chromium coating is denoted generally by the reference numeral 46.
  • a chromium coating in the manner of the chromium coating identified by the reference numeral 46 in Figure 5 of the drawing to the outer circumference of a tubular member such as the tubular member 44 illustrated in Figure 5 of the drawing
  • the following steps in accord with the practice of the subject matter of this aspect of the present invention are preferably performed.
  • a stationary foundation such as the stationary foundation 12 made of a suitable cast refractory material which is depicted in Figure 1 of the drawing.
  • a plurality of supports such as the plurality of supports 14 shown in Figure 1 of the drawing are positioned on the stationary foundation in suitably spaced relation one to another.
  • a retort having a cover and embodying preferably a construction such as that of the retort 16 depicted in Figures 1, 2 and 3 of the drawing is suitably placed absent the cover thereof on the plurality of supports so as to thereby be suitably supported by the stationary foundation.
  • a layer of powder approximately one-half inch (12.7 mm.) thick is spread evenly over the bottom of the retort.
  • the powder employed for this purpose is in the form of a mixture consisting of 3% ammonium chloride, 55% alumina and 42% ferrochromium.
  • a first layer of tubular members 44 is placed on this layer of powder which has been spread over the bottom of the retort.
  • air is first purged from the interior of each tubular member 44 by passing an inert gas such as argon through the interior of each of the tubular members 44.
  • an inert gas such as argon
  • a suitably constructed plug preferably of sheet-metal construction, is suitably installed in each end of each of the tubular members 44 so as to bear a tight-fitting relation thereto.
  • a layer of tubular members 44 and a layer of the same powder mix and in the same thickness of approximately one-half inch (12.7 mm.) are alternately added to the retort until the retort's capacity to receive layers of tubular members 44 is reached, or until the desired number of layers of tubular members 44 has been emplaced in the retort if this number of layers of tubular members 44 is less than the number of layers of tubular members 44 that is required to reach the retort's capacity for receiving such items.
  • each such layer of tubular members 44 is identified in Figures 2 and 3 by the same reference numeral 48 and each such approximately one-half inch (12.7 mm.) thick of powder including the layer thereof that is spread over the bottom of the retort is identified in Figures 2 and 3 by the same reference numeral 50.
  • this last layer 48 of tubular members 44 is covered by a layer, denoted in Figure 2 by the reference numeral 52, of approximately four inch (101.6 mm.) thickness of the same mix of powder as that of the other layers 50 of powder which in accordance with the preceding description have previously been provided in the interior of the retort.
  • the cover to the retort is then positioned thereon and is sealed in place by being welded thereto.
  • the inlet passage means and the outlet passage means with which the retort is suitably provided are connected in fluid flow relation to a suitable supply of a fluid medium, e.g., an inert gas such as argon, suitable for accomplishing a purging of air from the interior of the retort.
  • a fluid medium e.g., an inert gas such as argon
  • the furnace is suitably moved, such as through the engagement by a conventional industrial-type crane with the lugs with which the furnace is suitably provided for this purpose, into surrounding relation to the retort whereby the heating means of the furnace is capable of heating the layers 48 of tubular members 44 that have been emplaced within the retort in the manner that has been described hereinabove.
  • the inlet passage means and the outlet passage means with which the furnace is suitably provided are connected in fluid flow relation with a suitable supply of a fluid medium, e.g., an inert gas such as argon, suitable for effecting a purging of air from within the furnace, i.e., from within the area surrounding the retort.
  • a fluid medium e.g., an inert gas such as argon
  • the heating of the layers 48 of tubular members 44 by the heating means of the furnace is then commenced. Simultaneously with the commencement of the heating of the layers 48 of tubular members 44 by the heating means of the furnace, a flow of an inert gas is begun through the inlet passage means of the retort into the interior of the retort and through the inlet passage means of the furnace into the area within the furnace that surrounds the retort. During the course of this heating up of the layers 48 of tubular members 44 emplaced within the retort there are fumes generated.
  • these fumes are carried out of the retort through the outlet passage means with which the retort is suitably provided by the inert gas flowing through the retort, and are carried out of the area within the furnace located in surrounding relation to the retort through the outlet passage means with which the furnace is suitably provided by the inert gas flowing through the furnace.
  • these fumes as well as the inert gases exiting through the outlet passage means of the retort and the outlet passage means of the furnace are in accordance with the illustrated embodiment of the invention caused to flow into and through a stack, the latter being denoted generally by the reference numeral 54 in the drawing, before being discharged to the atmosphere.
  • these fumes begin to build up they are ignited in any suitable manner through the use of any conventional form of igniting means (not shown) suitable for use for such a purpose.
  • This igniting of the fumes is made to occur after the fumes leave the retort and the area within the furnace located in surrounding relation to the retort such that the fumes are burned off before they can be discharged from the stack 54 to the atmosphere.
  • This heating of the layers 48 of the tubular members 44 that are emplaced in the retort by the heating means of the furnace and the flow of the inert gas through the retort and through the area within the furnace located in surrounding relation to the retort continues until in the case, for example, wherein the chromium coating to be applied is to be applied to the outer circumference of the tubular members 44, the coolest location in the retort has reached a first predetermined temperature of 2100°F. (1149°C) Moreover, this predetermined temperature of 2100°F. (1149°C) is thereafter continuously maintained for a preestablished period of ten hours.
  • the predetermined temperature to which such other articles may need to be heated in order to successfully accomplish the application of a chromium coating to one or more surfaces thereof may vary, i.e., may be other than 2100°F. (1149°C), e.g., a lesser temperature than 2100°F. (1149°) such as a temperature lying in the range of 1700°F. (927°C) to 2100°F. (1149°C).
  • the preestablished period of time for which the predetermined temperature must be continuously maintained for purposes of successfully accomplishing the application of the chromium coating to one or more of the surfaces thereof may need to be other than ten hours, e.g., for some period in excess of ten hours.
  • the heating means of the furnace is turned off and the flow of inert gas through the interior of the retort and through the area of the furnace that surrounds the retort is shut off whereupon a cooling down of the layers 48 of tubular members 44 emplaced in the retort commences.
  • This cooling down of the layers 48 of the tubular members 44 emplaced in the retort continues until the hottest location within the retort has cooled down to a second predetermined temperature.
  • this second predetermined temperature is 400°F (204°C). It is to be understood here though that for applications wherein the nature of the chromium coating to be applied is other than the application of the chromium coating to the outer circumference of a tubular member 44 for purposes of successfully accomplishing the application of the chromium coating to one or more surfaces of the particular article in question this second predetermined temperature may vary, i.e., may be other than 400°F. (204°C). Once the hottest location in the retort has cooled down to the second predetermined temperature of 400°F.
  • the inlet passage means and the outlet passage means of the furnace are suitably disconnected so as to enable the furnace to be removed from in surrounding relation relative to the retort.
  • the furnace is then removed from in surrounding relation relative to the retort through the engagement by a conventional industrial-type crane with the lugs with which the furnace is suitably provided for this purpose.
  • the inlet passage means and the outlet passage means are likewise similarly disconnected.
  • the cover is removed from sealing engagement with the retort.
  • the tubular members 44 After the cover has been removed from the retort, the residual powder remaining in the retort and the layers 48 of tubular members 44 emplaced within the retort are removed therefrom. Each tubular member 44 is then cleaned off, i.e., any residual powder remaining thereon is removed therefrom. If there exists a need therefor, the tubular members 44 are then heat treated. Once the tubular members 44 have been so heat treated, they are inspected for physical integrity and as needed the tubular members 44 are subjected to a straightening operation in order to correct any deformation to which the tubular members 44 may have been subjected in the course of having the chromium coating applied to the outer circumference thereof.
  • any weld connections that may be required to be made to the tubular members 44 are made thereto and/or any other associated fabrication to which the tubular members 44 may need to be subjected is performed thereon.
  • the tubular members 44 to the extent required thereby are once again subjected to heat treatment, whereupon the last step in the successful accomplishment of the application of the chromium coating 46 to the outer circumference of each of the tubular members 44 that needs to be performed, i.e., that of performing a final inspection of each of the tubular members 44, is conducted.
  • the subject method in accord with this aspect of the present invention is equally applicable for use for purposes of applying a chromium coating to one or more of the surfaces of an article such as, by way of exemplification and not limitation, the joined tubular members denoted generally by the reference numerals 56 and 58 in Figure 4 of the drawing wherein the joined tubular members 56 and 58 are illustrated with chromium coatings denoted generally by the reference numerals 60 and 62 applied to the inner circumference and to the outer circumference, respectively, thereof, or such as the non-tubular member, denoted generally by the reference numeral 54 in Figure 6 wherein the non-tubular member 64 is illustrated with a chromium coating denoted generally by the reference numeral 66 applied to all of the outer surfaces thereof.
  • the chromium coating that results from the practice of the subject method in accord with this aspect of the present invention may be subjected to shot peening thereby rendering it possible to realize all of the benefits that are known to accrue from subjecting a surface to shot peening without adversely affecting the efficacy of the chromium coating itself, i.e., the capability of the chromium coating to resist corrosion.
  • chromizing consists of the submerging within a retort in a powder mixture containing a chromium component the steel article or articles to which a chromium coating is to be applied to one or more surfaces thereof, followed by the sealing of the retort and then the heating of the retort and its contents to a predetermined elevated temperature in a furnace for a preestablished period of time, i.e., for several hours.
  • the chromium component in the powder mixture gasifies and in doing so deposits on the surface or surfaces of the steel article or articles that are submerged in the powder mixture within the retort such that the chromium diffuses into the metal, i.e., the surface or surfaces of the steel article or articles, to a depth and concentration that is dependent upon numerous metallurgical and process variables.
  • the result is an iron-chromium alloy coating on the surface or surfaces of the steel article or articles, which is metallurgically bonded as an integral part of the base metal. Being a diffusion process, the structural modification occurs in the surface, not on the surface.
  • grain boundary carbides are characteristically present in chromized structures. Moreover, it is also known that these grain boundary carbides can produce a susceptibility of the chromium coating to intergranular attack in some service environments. Therefore, at least for these service environments it is desirable that the amount of grain boundary carbides that are present in the chromium coating be minimized to the extent possible.
  • a new and improved apparatus for applying a coating of chromium to one or more of the surfaces of an article as a means of providing protection thereto.
  • a new and improved method for applying a coating of chromium to one or more of the surfaces of an article as a means of providing protection thereto there is provided.
  • an apparatus and a method are provided for applying a coating of chromium to one or more of the surfaces of an article wherein the surfaces to which the coating of chromium is applied may be the external and/or the internal surfaces of the article.
  • the apparatus and the method of the present invention for applying a coating of chromium to the surface of an article is characterized in that the chromium coating that is applied in accord therewith is thicker than that which it has heretofore been possible to provide through the use of prior art chromium coating methods. Additionally, in accordance with the present invention an apparatus and a method is provided for applying a coating of chromium to the surface of an article wherein the chromium coating that is applied in accord therewith contains a higher concentration of chromium than that which heretofore it has been possible to achieve through the use of prior art chromium coating methods.
  • the apparatus and the method of the present invention for applying a coating of chromium to the surface of an article is characterized in that the article to the surface of which in accord therewith the chromium coating is applied is larger in size than the size of the articles to which it has heretofore been possible to apply a chromium coating to the surface thereof through the use of prior art chromium coating methods.
  • an apparatus and a method is provided for applying a coating of chromium to the surface of an article which are relatively inexpensive to provide, which are relatively easy to employ and which are characterized in that the chromium coating provided thereby is better capable of resisting corrosion than the chromium coatings which heretofore have been available for use for the same purpose.

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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)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Furnace Details (AREA)
EP89908116A 1988-06-24 1989-05-19 Apparatus for and method of chromizing articles Expired - Lifetime EP0420939B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US210906 1980-11-28
US21090688A 1988-06-24 1988-06-24

Publications (2)

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EP0420939A1 EP0420939A1 (en) 1991-04-10
EP0420939B1 true EP0420939B1 (en) 1993-08-25

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EP (1) EP0420939B1 (fi)
JP (1) JPH0613750B2 (fi)
KR (1) KR920004505B1 (fi)
CN (1) CN1015479B (fi)
AU (1) AU624848B2 (fi)
BR (1) BR8907514A (fi)
CA (1) CA1330743C (fi)
DE (1) DE68908705T2 (fi)
ES (1) ES2014674A6 (fi)
FI (1) FI906324A0 (fi)
IN (1) IN171976B (fi)
MX (1) MX171041B (fi)
WO (1) WO1989012701A1 (fi)

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CN101126146B (zh) * 2007-09-21 2010-06-23 南京利民机械有限责任公司 一种使用井式炉渗铬的方法
CN103510042B (zh) * 2013-09-08 2016-08-17 青岛征和工业股份有限公司 精密零件表面渗铬自动热处理装备
US9970094B2 (en) * 2014-01-14 2018-05-15 Praxair S.T. Technology, Inc. Modified slurry compositions for forming improved chromium diffusion coatings
JP6637231B2 (ja) * 2014-10-07 2020-01-29 エア・ウォーターＮｖ株式会社 金属の表面改質方法および金属製品

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2836513A (en) * 1956-04-10 1958-05-27 Metal Diffusions Inc Chromizing, adhering coating
US3585068A (en) * 1966-06-07 1971-06-15 Albright & Wilson Chromising of ferrous metal substrates
GB1347846A (en) * 1970-11-06 1974-02-27 Head Wrightson & Co Ltd Chromised ferrous metal article and a process for the production thereof
GB1379731A (en) * 1971-01-05 1975-01-08 Albright & Wilson Chromising ferrous metal substrates
FR2576917B1 (fr) * 1985-02-01 1987-04-24 Centre Nat Rech Scient Procede en caisse de formation de revetements protecteurs sur des pieces en alliages refractaires et dispositif pour sa mise en oeuvre
US4566534A (en) * 1985-02-01 1986-01-28 Camco, Incorporated Solenoid actuated well safety valve
US4596526A (en) * 1985-03-04 1986-06-24 Worthington Industries, Inc. Batch coil annealing furnace and method
DE3720251C1 (en) * 1987-06-19 1988-03-24 H-Peter Prof Charles Method for cleaning the off-gases from the annealing chamber (carburizing chamber, case-hardening chamber) of annealing installations in the steel industry

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Publication number Publication date
JPH0613750B2 (ja) 1994-02-23
DE68908705D1 (de) 1993-09-30
CA1330743C (en) 1994-07-19
AU3965689A (en) 1990-01-12
IN171976B (fi) 1993-02-27
AU624848B2 (en) 1992-06-25
DE68908705T2 (de) 1994-02-24
KR920004505B1 (ko) 1992-06-08
JPH03501979A (ja) 1991-05-09
WO1989012701A1 (en) 1989-12-28
MX171041B (es) 1993-09-27
BR8907514A (pt) 1991-05-28
CN1039624A (zh) 1990-02-14
KR900702072A (ko) 1990-12-05
CN1015479B (zh) 1992-02-12
EP0420939A1 (en) 1991-04-10
FI906324A0 (fi) 1990-12-20
ES2014674A6 (es) 1990-07-16

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