EP0455812A1 - Procede de pulverisation au gas-plasma de revetements metalliques - Google Patents

Procede de pulverisation au gas-plasma de revetements metalliques Download PDF

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Publication number
EP0455812A1
EP0455812A1 EP90913571A EP90913571A EP0455812A1 EP 0455812 A1 EP0455812 A1 EP 0455812A1 EP 90913571 A EP90913571 A EP 90913571A EP 90913571 A EP90913571 A EP 90913571A EP 0455812 A1 EP0455812 A1 EP 0455812A1
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EP
European Patent Office
Prior art keywords
plasma
coating
particles
spraying
enthalpy
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.)
Withdrawn
Application number
EP90913571A
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German (de)
English (en)
Inventor
Mikhail Valentinovich Karasev
Valery Stepanovich Klubnikin
Georgy Konstantinovich Petrov
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Leningradsky Politekhnichesky Institut
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Leningradsky Politekhnichesky Institut
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Publication of EP0455812A1 publication Critical patent/EP0455812A1/fr
Withdrawn legal-status Critical Current

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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
    • 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
    • C23C4/134—Plasma spraying

Definitions

  • the present invention relates to the field of plasma treatment technology and, more specifically, to plasma spraying processes used to produce metal coatings and using compressed air as plasma-forming medium.
  • the invention can be used by any industry to obtain both general- and special-purpose coatings, preferably for hardening and reconditioning machine components.
  • the conventional plasma spraying methods using for plasma-forming media such inert gases as argon, helium, etc. as well as their mixtures with nitrogen, are capable of providing a sufficiently high quality of deposited metal coatings.
  • the plasma jet formed of one of the aforementioned media will change its gas composition with distance from the plasma generator nozzle.
  • the plasma jet is formed entirely of the working fluid, while at increasing distances from the nozzle edge there is increasingly vigorous entrainment of atmospheric air by the jet (A. Hasui and O. Morigaki. "Naplavka i napylenie", 1985, The Mashinostroenie Publishers, Moscow, p.145).
  • Air plasma spraying technology relates to the new route of development in spraying technology, i.e. to plasma spraying in active media, which has presently gained a wide scope of application.
  • the active media used include air, air and natural gas mixtures, carbon dioxide and natural gas mixtures, water vapour, etc.
  • a common feature of all these gas media is the presence therein of chemically active oxygen.
  • chemically active oxygen will limit the use of plasma spraying of metal powders because of plasma chemical interaction processes between plasma and metallic material.
  • control of metal coating oxidation may be effected by suitable selection of air plasma spraying process parameters, such as powder particle size distribution, plasma jet enthalpy, plasma jet power, plasma-forming gas flow rate, and others (V.S. Klubnikin et al. "Promyshlennoe primenenie protsessov vozdushno plazmennogo napylenia pokryty", 1987, The LDNTP Publishers, Leningrad, p.15).
  • oxidation of metal powders in air plasma will increase with lower particle size and lower particle velocity, therefore in laminar plasma flow the burning loss of alloying components and the extent of oxidation of particles is considerably higher than in turbulent plasma flow.
  • air plasma spraying process parameters are largely dependent upon plasma generator operating parameters, such as plasma generator arc current, arc voltage, and plasma-forming gas flow rate. Selection of optimal process parameter values, such as would assure the obtainment of low-oxidized coatings, is fairly complicated and labour-consuming owing to the large range of variations in the interrelated plasma generator process parameters.
  • a known plasma spraying method comprising the steps of introducing powder particles to be sprayed into a turbulent plasma jet, accelerating and heating them therein, and placing the component surface to be coated in the path of particle flow (JP, A, 57-126964). Formation of the plasma coating occurs by formation of fusion (weld) areas over the contacting surfaces of deformed particles within the coating. This is achieved by selecting the spraying distance such that molten particles should be deposited over the component surface at their melting temperature, and the coating, as well as the component surface, should not be overheated.
  • the coating quality is enhanced by optimizing the particle size of the powder to be sprayed. It will be considered that the method here is one of plasma spraying in inert gas and that the coating properties implied are those of density and adhesive strength.
  • plasma spray coating methods in which the coating quality is controlled by varying the operating variables of the plasma generator, i.e. arc current, arc voltage, and plasma-forming gas flow rate (FR, A, 2526331; DE, A, 3216025). Said methods are likewise designed for plasma spray coating based on the use of inert gases, by preference.
  • the recommendation is for the maximum arc current and plasma-forming gas flow rate values for the plasma generator used in order that high-quality coatings might be obtained (regarding, specifically, the desired density and adhesive strength). This is based on the condition that the coating density and adhesive strength will increase with increasing particle velocity and increasing particle temperature, with the particle temperature preferably exceeding the melting point of the particles.
  • the temperature, to which a particle will heat in a plasma jet is proportional to the enthalpy of the plasma jet, which is determined by the ratio of the jet heat output to the gas flow rate, so that arbitrary changes in said operating variables of the plasma generator may lead to particles heating up to a temperature exceeding their melting point and to the increased concentration of oxides in the coating.
  • said method there is no correlation between the plasma jet parameters and the particle size of the material to be sprayed, this also resulting in an increased concentration of oxides in the coating applied.
  • the plasma spraying process parameters to provide the specified coating properties are determined experimentally as follows. Sprayed particle velocity and temperature are measured at the coating location, the quality of the coating formed is investigated, and the plasma spraying process parameters (current arc, plasma-forming gas flow rate, plasma jet power, particle size, etc.) are optimized in accordance with the results obtained. This method is preferably designed for spraying in inert gases, therefore the coating is investigated for such properties as adhesion, porosity, hardness, and cohesion whereas the oxidation of the coating is not considered. In this connection, the process variables are optimized based on the particles molten state which can be realized within a wide range of temperatures - from the melting point to the evaporation temperature.
  • the present invention is based upon the objective of providing an air plasma spraying method wherein the spraying process parameters would be so interrelated and their limits would be determined such that a minimal concentration of oxides would be ensured in the coating formed, thus enhancing the quality of the coating and simplifying the process.
  • the range of plasma jet enthalpy values, the maximum and minimum allowable values for plasma-forming gas flow rate and plasma jet power, respectively, and said limitation on the minimum size of particles to be sprayed, combine to define the boundaries of the proposed region of air plasma spraying process parameters to produce metal coatings.
  • the process parameters plasma-forming gas flow rate, plasma jet power, and sprayed particle size
  • the explanation lies in the fact that the region as defined by the inventors, is close in process conditions to the commencement of coating formation.
  • the deposition of particles over the component surface in this case and the formation of the coating occur with the metal particles being heated to a temperature not exceeding practically their melting point and having the maximum possible velocity.
  • the region of process parameters to provide for the formation of a low-oxidized coating is shifted towards higher gas flow rate and higher plasma jet power while for high-melting materials it is shifted towards lower gas flow rate and lower plasma jet power.
  • Increasing the size of powder particles to be sprayed will expand the region of allowable process parameters. This is due to the extended range of plasma jet enthalpy values. In all events, the obtainment of a low-oxidized coating requires the plasma-forming gas flow rate to be sufficient to provide for turbulent plasma flow.
  • the proposed region of spray coating parameters and, specifically, the optimal plasma generator operating parameters are determined by a design-and-experimental method, in contrast to the method according to DE, A, 3435748. Using a design-and-experimental method will reduce the number of technological experiments and lead to a lower level of labour consumption involved in the method.
  • Optimal air plasma spraying process parameters for a specific metal powder spraying process are selected from said region, using previously known procedures, and depending on the desired quality of the coating to be obtained (apart from oxidation) and on the required throughput rate of the spraying process.
  • the air plasma spraying method to produce metal coating is implemented as follows.
  • the exit section of the nozzle 1 ( Figure 1) of a plasma generator (not shown) serves to form an oriented air plasma stream 2 which forms a turbulent plasma jet 3 at exit from the nozzle 1.
  • the gas flow rate required to create turbulent flow is determined by known methods (Inkropera and Lepert, Yavleniya perekhoda techneniya v dozvukovoi plazmennoi strue". Raketnaya Tekhnika i Kosmonavtika, 1966, No.6, pp.164-165).
  • sprayed metal powder particles 5 are fed into the plasma jet 3, the turbulent jet 3 serving to accelerate and heat up said particles.
  • the sizes (d) of the particles 5 are selected by known methods, in relation to the required density and adhesive strength of the coating (V.S. Klubnikin, "Plazmennye ustroistva dlya naneseniya pokryty", Izvestiya Sibirskogo Otdeleniya Akademii Nauk SSSR, 1983, No.13, vol.2 (Novosibirsk), pp.82-92).
  • the size of the particles 5 should never be less than 20 ⁇ m.
  • Spraying distance is selected by known methods, based on the requirement for molten particles 5 to be deposited on the surface of the component 7 at their melting temperature and for the coating 8 and the surface of the component 7 to be prevented from overheating (A.V. Donskoy and V.S. Klubnikin, "Elektroplazmennye protesessy i ustanovki v mashinostroenii", 1979, The Mashinostroenie Publishers, Leningrad, p.192; A. Hasui and O. Morigaki, “Naplavka i napylenie", 1985, The Mashinostroenie Publishers, Moscow, p.173).
  • Overheating of the coating 8 will generally lead more especially in air plasma spray coating, to their vigorous oxidation.
  • high-melting metal powders i.e. where the temperature is sufficiently high before the powder material begins to be oxidized vigorously, the surface temperature of the coating 8 and the component 7 - such that would preclude their overheating - is maintained by suitably selecting the spraying distance.
  • low-melting metal powders when a relatively slight overheating of the coating 8 will initiate vigorous oxidation thereof, the component 7 is additionally cooled by, e.g. compressed air.
  • any air-plasma metal-powder spraying process parameters out of said region will provide for the formation of a low-oxidized coating.
  • said optimal parameters are selected in each specific spray coating process in a comparatively simple way, following known procedures and based on the required coating quality (apart from the extent of oxidation) and process throughput rates.
  • Determining the boundaries of said process parameter region is by means of a design-and-experimental method which can be illustrated with the help of Figure 2.
  • This done, isometric lines plotted for the enthalpies H1 and H2 in the coordinates P and G from the relation H P/G, which lines in said coordinates are straight lines with coefficients of proportionality H1 and H2.
  • arc current and plasma-forming gas flow rate values for the plasma generator, such that are required to obtain the values of enthalpies H1 and H2 and that of plasma jet power P.
  • Point D is determined as the point of intersection of line H2 and value P I .
  • a curve 9 is plotted to define a region 10 where the material used, in powder form, is deposited by way of air plasma spraying.
  • the curve 9 is formed as a number of points corresponding to the commencement of coating deposition based on the material selected, in powder form, at various plasma jet enthalpies and determined by means of standard technological experiments similar to those used for determining points A and B.
  • the process parameter region 11 characterized by the formation of low-oxidized coating will be defined by the isometric lines H1 and H2, gas flow rate G II , plasma jet power P 1 , and powder spray coating curve 9 to give region of optimal process parameters.
  • the region 11 is shown in the form of a figure having vertices A,B, and D.
  • a region 12 comprised in the powder spray deposition region 10 is a process parameter region which is characterized by the formation of oxidized coatings.
  • the process parameter region defined by isoline H1 and curve 9, is characterised by deposition of coating which are lower in cohesion, adhesion, density and other properties. This is due to the low arc current failing to provide for an optimal combination of particle velocity and particle temperature and to the formation of a coating having fused sections between particles.
  • the optimal process parameter region 11 is shifted towards higher gas flow rates.
  • the commencement of coating deposition at H2 0.69 ⁇ d (intersection of isoline H2 and curve 9) is achieved in this case at substantial gas flow rates (point G1 is shifted to the right).
  • the commencement of coating deposition at H2 0.69 ⁇ d (intersection of isoline H2 and curve 9) is shifted towards lower gas flow rates.
  • the optimal process parameter region 11 is narrowed in this case as compared to the case of low-melting powder spraying.
  • the optimal process parameter region occupies an intermediate position.
  • Table 1 cites specific spraying process parameter values and coating oxidation estimates.
  • point C is between points B and D on the straight line H2
  • point D is the point of intersection of the value of P I and the straight line H2.
  • the extent of coating oxidation was estimated by way of visual inspection.
  • a sampling analysis was performed for oxygen concentration in coatings obtained from the following powders: nickel- aluminium, iron-based alloy, and nickel-chromium-boron- silicon alloy with an addition of tungsten (Table 2). Analysis for oxygen concentration was performed in a Leko unit (USA), and powder particle size analysis in a Gilas unit.
  • an air plasma generator was used, with an arc channel length of 35 to 53 mm.
  • a bank of DC sources was used as a power supply unit.
  • a powder meter was utilized for powder feeding. The spraying distance was selected equal to 140-200 mm. Spraying nickel-chromium-boron-silicone alloy, tungsten and tin powders with a particle size of 19.3 ⁇ m has demonstrated that an oxidized coating is formed whatever the spraying conditions.
  • the proposed method can be used to best advantage in the application of metal coatings, preferably for hardening and reconditioning machine components.

Abstract

Un procédé de pulvérisation au gas-plasma de revêtements métalliques consiste à acheminer, à accélérer et à chauffer des particules métalliques en poudre (5) dans le jet de plasma, et à placer la surface des articles (7) à revêtir sur le chemin des particules (5), les dimensions des particules (5) introduites dans le jet n'étant pas inférieur à 20 mum. La pulvérisation des revêtements est effectuée à l'enthalpie du jet de plasma (3) définie par la relation suivante: H = (0,46 - 0,69)Sm(r)d, dans laquelle H représente l'enthalpie du jet de plasma (3) dans kJ/g, d représente la dimension moyenne des particules (5) pulvérisées; la consommation en gaz formant le plasma est maintenue à une valeur ne dépassant pas celle correspondant au point de départ de la sédimentation du revêtement (8) à l'enthalpie du jet de plasma (3) H = 0,69 d, tandis que la puissance du jet de plasma (3) est maintenue à une valeur correspondant au point de départ de sédimentation du revêtement (8) à l'enthalpie H = 0,46 d.
EP90913571A 1989-12-01 1990-01-15 Procede de pulverisation au gas-plasma de revetements metalliques Withdrawn EP0455812A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SU4761083 1989-12-01
SU4761083/02A SU1835865A1 (ru) 1989-12-01 1989-12-01 Способ воздушно-плазменного напыления металлических покрытий

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EP0455812A1 true EP0455812A1 (fr) 1991-11-13

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EP (1) EP0455812A1 (fr)
AU (1) AU6331490A (fr)
SU (1) SU1835865A1 (fr)
WO (1) WO1991008321A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001032949A1 (fr) * 1999-10-30 2001-05-10 Agrodyn Hochspannungstechnik Gmbh Procede et dispositif servant au revetement par plasma de surfaces
EP1340834A2 (fr) * 2002-02-27 2003-09-03 Sulzer Metco AG Revêtements de surfaces de contact de cylindres pour moteurs à combustion et procédé de sa fabrication
EP2290117A1 (fr) * 2009-08-27 2011-03-02 General Electric Company Procédé de dépôt de revêtements protecteurs sur des composants à combustion de turbine
WO2018228743A1 (fr) * 2017-06-12 2018-12-20 Siemens Aktiengesellschaft Procédé de revêtement d'une surface d'un composant par projection thermique

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2503739C2 (ru) * 2011-10-25 2014-01-10 Российская Федерация, от имени которой выступает Министерство промышленности и торговли Российской Федерации (Минпромторг России) Способ нанесения покрытий с использованием дуги пульсирующей мощности

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL7600738A (nl) * 1976-01-23 1977-07-26 Plasmainvent Ag Inrichting voor het plasma-spuiten.
SU656669A1 (ru) * 1976-07-13 1979-04-15 Предприятие П/Я М-5729 Сопло дл плазменной горелки

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9108321A1 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001032949A1 (fr) * 1999-10-30 2001-05-10 Agrodyn Hochspannungstechnik Gmbh Procede et dispositif servant au revetement par plasma de surfaces
US6800336B1 (en) 1999-10-30 2004-10-05 Foernsel Peter Method and device for plasma coating surfaces
EP1340834A2 (fr) * 2002-02-27 2003-09-03 Sulzer Metco AG Revêtements de surfaces de contact de cylindres pour moteurs à combustion et procédé de sa fabrication
EP1340834A3 (fr) * 2002-02-27 2004-03-31 Sulzer Metco AG Revêtements de surfaces de contact de cylindres pour moteurs à combustion et procédé de sa fabrication
EP2290117A1 (fr) * 2009-08-27 2011-03-02 General Electric Company Procédé de dépôt de revêtements protecteurs sur des composants à combustion de turbine
WO2018228743A1 (fr) * 2017-06-12 2018-12-20 Siemens Aktiengesellschaft Procédé de revêtement d'une surface d'un composant par projection thermique

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Publication number Publication date
WO1991008321A1 (fr) 1991-06-13
SU1835865A1 (ru) 1996-04-10
AU6331490A (en) 1991-06-26

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