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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D23/00—Casting processes not provided for in groups B22D1/00 - B22D21/00
  • B22D23/003—Moulding by spraying metal on a surface
• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
  • C23C4/123—Spraying molten metal
• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
  • C23C4/131—Wire arc spraying

Definitions

• the present invention relates to a spray deposition process and in particular to a metallurgical spray deposition process.
• the process is also useful for producing thick and thin coatings and other sprayed metal deposits sprayed onto substrates of all kinds, particularly where some of the topographical features are difficult to cover or fill due to complex geometries.
• the manner in which sprayed droplets impinge, spread and solidify on deposition is critical in influencing the subsequent properties of the manufactured coating or deposit.
• the first droplets to be deposited will determine the properties at the coating/substrate interface.
• the first deposited droplets determine the accuracy of replication and tooling wear properties.
• droplet deposition behaviour controls the bulk microstructure (such as volume fraction, morphology and size of porosity) consequently determining the coating or deposit bulk properties.
• droplet rebounding or splashing leads to a reduction in process yield. Recent experimental evidence suggests that droplet splashing occurs to a significant and greater extent than previously believed.
• a further problem with sprayforming onto patterns or substrates having an object surface of varied (three dimensional) topography arises due to the fact that metal spray processes are "line of sight” processes in which known effects of shadowing and bridging occur for certain configurations of object surface topography.
• a further problem occurs at internal and external edges of object surface topography, where poor quality deposit integrity can occur resulting in poor quality integrity to the deposit. This can result in flaking or crumbling of the deposit at corners and edges.
• a process for producing a metallic tool, mould, die or other body of significant thickness or a coating comprising directing a spray comprising molten metallic droplets carried by a propelling gas toward an object surface of a substrate or pattern so as to build up a metallic deposit or coating comprising the mould, tool, die, body or coating on the object surface of the substrate or pattern, wherein at one or more predetermined stages during spraying droplets of a relatively large mean size are sprayed and at one or more other stages droplets of a relatively smaller mean size are sprayed.
• the relatively larger droplets are preferably sprayed at a stage preceding the spraying of relatively smaller droplets.
• the spraying of the relatively larger droplets is dependent upon the nature of and/or the location of the topographical relief features.
• metallic spray droplets of mean diameters of substantially 200 microns and above produce highly beneficial results. This result is surprising because trends in spray deposition research and practices have herebefore tended to suggest that finely sprayed droplets and relatively higher droplet spray velocities should produce improved results during the manufacture of coatings and most other products when using spray deposition techniques. Smaller droplet sizes have also been preferred because deposit porosity is minimised by using smaller droplet sizes. This is one of the premises behind the development of techniques such as plasma spraying and high velocity oxy-fuel metallic spraying techniques.
• the propelling gas of the spray is within a pressure range lower than that normally recommended for use with a particular metal spraying apparatus.
• the operating pressure will therefore be different for different equipment, but is preferably at or about 3 bar or less. This results in the relatively large droplets desired, and relatively low droplet velocities compared with known techniques.
• the droplets are produced by arc spraying, because arc spraying typically produces coarser droplet sizes than other known spray deposition processes.
• Conventional arc spraying apparatus has however not been designed for spraying at the larger droplet sizes of the present invention and modification and frequent cleaning of arc spray guns during proving of the invention has been found to be necessary. It is believed that this is strongly indicative of the process of spraying metallic droplets at the dimensions preferred being novel and inventive per se.
• Preferably relatively high currents are used in the arc spraying process compared with the currents used in conventional arc spraying techniques.
• O-A-96/09421 discloses metallurgical spray deposition techniques which may be used to control internal stresses in deposited bodies.
• the relatively large droplet sizes required to improve reproduction of detail and edge definition from the object surface of the substrate or pattern (and also to inhibit bridging or shadowing) have however been found not to be suitable for control of stresses. It is therefore preferred that in the process according to the invention, process parameters are varied such that the relatively larger droplets are sprayed during the period and over the areas where detail of the substrate is required to be reproduced. Relatively smaller droplets are sprayed after the period when the detail has been replicated as required, and in other portions of the deposit where it is not required to replicate detail, preferably under conditions to control internal stresses in the deposit.
• the process according to the invention may comprise initial spraying of relatively large droplets onto the object surface of the substrate or pattern where detail replication is required (such as, for example, edge definition is to be reproduced, and/or where shadowing is to be avoided) , and then subsequent modification of the spray parameters, (preferably as soon as possible after the said pattern detail and edge definition have been achieved) , so as to spray relatively smaller droplets onto the object surface of the pattern or substrate. (Preferably in order to bring stress control into operation, as described, for example, in WO-A- 96/09421) .
• the process may comprise spraying of relatively large droplets from one spray source onto the object surface of the substrate or pattern where detail is required (such as edge definition is to be reproduced, and/or shadowing effects are to be ameliorated) , and introducing a further spray of relatively smaller metallic droplets from a second spray source (preferably concurrently with the first spray) , the further spray preferably being tailored to minimise internal stresses in the deposit.
• control step c) is operated by control means (preferably computer control means) and preprogrammed.
• one or more spray guns are preferably mounted on manipulator means, such as an industrial robot which is preferably programmed, advantageously together with the spray guns, by the control means.
• manipulator means such as an industrial robot which is preferably programmed, advantageously together with the spray guns, by the control means.
• the one or more sprays of metallic droplets generated by the spray guns may be scannable, in which case the means for scanning the sprays is preferably co-ordinated and controlled, preferably by the same control means.
• Figures 1(a) and 1(b) are explanatory sectional views of known spray deposition processes, highlighting the problem of shadowing and bridging known in the prior art.
• Figure 2 is a schematic view of apparatus for use in the process according to the invention.
• FIG. 1(a) there is shown a substrate 101 rotated beneath a pair of arc-sprayed metallic droplet sprays 103 and 104.
• the arc sprayed metallic droplets are sprayed from two arc spray guns mounted on a 6-axis industrial robot (not shown) to produce a sprayed footprint 102, which is moved over the substrate by the robot manipulating the guns together, to produce a deposit 105 re-producing the object surface 106 of the substrate 101.
• the surface topography of object surface 106 is such that it is provided with a channel 107 having a pair of parallel sides 107a, 107b and a perpendicular surface 107c.
• the sprayed deposit 105 builds up on the object surface 106 eventually bridges the width of channel 107 leaving a void 108, as -hown in Figure 1(b) caused by the shadowing effect of the build up of deposit 105.
• the apparatus of Figure 2 comprises arc spray guns 1,2 mounted on a 6-axis industrial robot 10, producing atomised metal sprays 3,4 which impinge upon pattern or substrate 5.
• Pattern or substrate 5 sits on a rotating table 6, and is provided with a varied topography object surface 7.
• a computer control arrangement 8 is used to control manipulation of the robot 10, and also coordinate and control process parameters of the respective sprays 3,4 produced by guns 1,2 (such as, for example, the gas spraying pressure, and wire feed rate/current of the respective guns 1,2).
• the apparatus is completely enclosed within a dustproof acoustic chamber 9, connected to an appropriate dust and fume extraction system (not shown) .
• Both spray guns 1,2 were used to spray low carbon steel (from stock feed wire) .
• an initial spray droplet size of approx. 350 microns could be achieved by means of propelling compressed gas at a pressure of 2.6 bar. These conditions were maintained for a period of approximately 120 seconds, for both spray guns. This length of time was sufficient to ensure that all internal and external edges of the object surface of the substrate were covered by deposited spray having droplets of average diameter 350 microns approx.
• Spraying parameters for both arc spray guns were then adjusted by increasing the pressure of the propelling gas to 3.5 bar and simultaneously decreasing the current supply in order to decrease the rate of generation of molten metal in the arc. These conditions were used to produce a finer droplet size below 150 microns for building up the remainder of the deposit, and to control stresses according to WO-A-96/09421.
• the deposit was subsequently released from the substrate 5 and found to have improved edge integrity and less extensive shadowing or bridging defects than would have been the case when conventionally spraying with droplet sizes of less than 150 microns throughout the process.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Plasma & Fusion (AREA)
• Physics & Mathematics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Coating By Spraying Or Casting (AREA)
• Inorganic Insulating Materials (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Acyclic And Carbocyclic Compounds In Medicinal Compositions (AREA)

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• 1999
  • 1999-02-23 GB GBGB9903964.6A patent/GB9903964D0/en not_active Ceased
• 2000
  • 2000-02-23 ES ES00913569T patent/ES2251364T3/es not_active Expired - Lifetime
  • 2000-02-23 WO PCT/US2000/004494 patent/WO2000050177A1/fr active IP Right Grant
  • 2000-02-23 DE DE60023120T patent/DE60023120T2/de not_active Expired - Lifetime
  • 2000-02-23 EP EP00913569A patent/EP1159085B8/fr not_active Expired - Lifetime
  • 2000-02-23 AT AT00913569T patent/ATE306343T1/de not_active IP Right Cessation

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