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WEAR-RESISTING AND CORROSION-RESISTING PRODUCTS AND TECHNOLOGIES FOR POWER PLANT, CHEMICAL PLANT, STEEL PLANT, CEMENT WORKS EQUIPMENTS, ETC.
 
Excellent Supersonic Arc Spraying Tenchnology
CAS-400Excellent Supersonic Arc Spraying Equipment
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Technological Project Identification Result of Zhejiang SAT (Zhejiang Technology Identify Character [2005] NO. 096)Patent Technology (ZL2004 2 0022150.4, 2004100178833)

EXCELLENT SUPERSONIC ARC SPRAYING TECHNOLOGY

      Arc spraying, especially Supersonic Arc Spraying, is a kind of thermal spraying technology which has developed and produced wide effects in recent years, thus it is much-regarded.
      Excellent supersonic arc spraying technology is a newest technology, it is developed and innovated on the basis of traditional supersonic arc spaying and has more excellent qualities. First, we developed the supersonic arc equipment, thus the output voltage, current become more equilibrium, the capability of anti-interference become stronger and more efficient, it can be used in worse work conditions for a long time; second, we made some reformations on wearing parts, for example, the current contact nozzle made great effects on working efficiency. By study-innovation of our company¡¯s scientific and technical group, we developed a new piece of current contact nozzle which possessed an unique construction (patented product), therefore, the service life advanced decuples, the spray painting efficiency also rised at the same time. Added to this, we also made inventions and creations on arc spray materials and spray layer structures, batch of excellent performance arc spray paint materials were innovated (patented product) in the past years. Experts of scientific and technological achievements all considered that our company had led the development of the home arc spraying technologies, and some portions had came up to an international advanced level.

       The operating principle of Excellent Supersonic Arc Spraying technology is: two alloy wires are put into the conductive spouts of arc spraying gun, which connect two high current and low voltage electrodes. When the wires go forward to get touch each other, they shall have a short circuit, they produce arc in which temperature will reach 5000¡æ. The heads of wires are molten and atomized to micro melted drops and then they shoot to the workpiece at the speed of more than 400m/s (supersonic) by compressing air flow (about twice velocity of sound), then a piece of arc spray layer is formed. 

Highlight of excellent supersonic arc spraying

      The output voltage and current of excellent supersonic arc spray equipment is very stabilization, the capability of anti-interference is strong, thus it can be used in abominable work conditions for a long time; the using life of the equipment is very long, furthermore, the wearing parts do not need to instead regularly.
      The binding strength of spray layer is up to 70MPa, and the traditional arc spraying only achieves 30~40Mpa. Jet velocity of particles is high, good atomizing, fine splats, formative spray plaint presents particularity, higher density (porosity¡Ü0.5%), so the spray layer¡¯s resistance to erosion and corrosion stability become higher.
       Excellent Supersonic Arc Spraying technology could use many kinds of metal wires and ceramic materials (solid wires and cored wires) : alloy wires, Mo, Al, Zn, Cu, copper alloy, Babbitt metal etc.. Anti-erosion and corrosion spray technology are used widely in power plant, such as water wall tubes, superheater tubes, economizer tubes of coal-fired boilers or circulation fluidized bed boilers, induced-draft fan¡¯s impeller and volute of the milling system, iron-printing machine¡¯s roller, printing machine¡¯s roller, paper machine¡¯s dryer, axletrees, pumps, valves, dies, chemical metallurgy equipments and parts.

     Higher spraying and source using efficiency, spraying alloy wires 40Kg each hour. No deformation of the workpieces occur, because  spraying temperature is under 100¡æ. There is also no effects on structure of them.
 
Equipment of excellent supersonic arc spraying

      The excellent supersonic arc spraying equipment (CAS-400) is mainly composed of high frequency inverse pulse power source, supersonic spraying gun, wire delivery machine, controlling system, compressing air system. Superior device, reliable performance, fine operation stability, the above points would provide
essential guarantee for obtaining a superior performance of spray coating.
     The main limbs of power source are composed of inward parts, so that the whole performance of this arc spraying equipment is very stable. There is little fault-arc and gun-blast during the run procedure. The power source is very stable and puts out in pulse form of current and voltage, sensitive adjust, so that alloy burning loss of spraying materials goes down greatly, the spray coating also looks more uniformity.
     Supersonic arc spraying gun is made according to principal of Laval gas flow. When compressed air flow goes through Laval cavum which has designed and made abortively, there is a ever accelerating process. When arriving at the exit, it becomes a high-speed current of air. The atomizing process goes on in the spraying gun. It is necessary that there is a good atomizing mouth in spraying gun for obtaining the stable particles fluid. The pulse current and voltage are helpful to atomizing.
     Wire delivery machine is very important. The wire delivery speed and its uniformity may directly affect stability of arc, atomizing effect of melted drop, spraying efficiency, etc.. the CAS-400 supersonic arc spraying machine¡¯s wire delivery machine is very stability.
    Patent designed Limbs as conductive spout could be used for a long time, thus it will improve the using time of wearing parts, work efficiency, and it is also useful to advance the spray coating¡¯s quality.
 
Technological procedure and structural design of supersonic arc spraying
  
      Pretreatment of workpiece and choice of spraying technique parameter may affect the qualities of spraying layer specially. Even the other conditions are all very well, once you choose a unfit pretreatment of workpiece or unfit spraying technique parameter, there will result in a unsuccessful spray coating.
 
Pretreatment of workpiece
      The pretreatment of boiler tubes of coal fired power plant divides into two steps. First, the ashes and oxides on the tube surfaces must be cleaned up completely by spraying 16-20 mesh Alumina or Silica sand. The surfaces ought not to remain any greasy dirt and moisture, reach the grade of Sa 2~3. Best sand blasting pressure: 0.6~0.8Mpa. Then, spraying 14~16 mesh Alumina to roughen surface, so as to enhance binding strength. Roughening process can also produce residual pressure stress that is helpful to increase fatigue strength. Best roughening sand blasting pressure: 0.5~0.7 MPa.
     The compressed air for sand blasting  has to be no water and no oil. The surface after pretreatment is clean and its activity degree is higher. So, arc spraying ought to be done within 2--4 hours, otherwise the surface is easy to corrode and pollute again.
 
Spraying technique parameter

Anti-erosion supersonic arc spraying
layer structure
arc voltage£¨V£©
Delivery current£¨mA£©
air pressure£¨MPa£©
layer thickness£¨mm£©
Functions and characteristics
First layer
£¨priming layer£©
36~38
110
0.5~0.6
0.1
spraying particle remains coarser, micro welding binding enhances binding strength
Second layer
£¨working layer£©
30~32
200
0.6~0.8
0.5~0.7
spraying particle extremely small, anti-erosion dense layer,
Third layer
£¨closing layer£©
£­
£­
0.3~0.5
0.1~0.2
Protecting as closing layer, good anti-erosion property.
 
 
Anti-corrosion supersonic arc spraying
layer structure
arc voltage£¨V£©
Delivery current£¨mA£©
air pressure£¨MPa£©
Spraying thickness£¨mm£©
Functions and characteristics
First layer
£¨priming layer£©
36~37
120
0.5~0.6
0.1~0.2
micro welding binding enhances binding strength
Second layer£¨working layer£©
29~31
180
0.6~0.8
0.2~0.4
spraying particle extremely small, anti-corrosion dense layer
Third layer
£¨closing layer£©
£­
£­
0.3~0.5
0.1
Protecting as closing layer, good corrosion resisting.
 
 
Design of spraying structure
 
      Because there are differences between workpiece¡¯s environmental medium, working temperature, velocity of medium flow, structural requirement and base material, using life, permit-improving condition, thus the protecting demands are different from each using characteristics. Therefore, the design of coating structure is very important, we must ensure a best functional performance as well as consider a best economical efficiency, we should make a comprehensive consideration on workpiece¡¯s working medium, working temperature, erosion and corrosion magnitude, base material¡¯s characteristic, spraying layer¡¯s performance, spraying layer¡¯s thickness, technical parameter etc., in order to design a best spraying structure.

    Spraying structural designers must have profound knowledge on materials science, surface strengthening theoretical knowledge, abundant spraying technology and spot application experience. CADRE corporation has a group of advanced technical manpower on investigating spraying layer and designing structure, we can carry through high standard technical designs and direct actual projects, provide best technical services to our customers.

    

                       
spot of anti-erosion supersonic arc spraying on boiler tubes     CADRE CAS-400 supersonic arc spraying machine
                             


                       
    spot picture of boiler water screen tube after spraying                CFB waterawall tubes                      with Cadre CP-HCrC coating for an overhaul period.

 


                
Application of excellent supersonic arc spraying technology on printing machine roller                         Different kinds of CADRE arc spray wires

   

                       
  Application of excellent supersonic arc spraying on superheater tubes of coal fired power plant            Anti-wear repairing of mechanical axletree workpiece.    

 

 

 
 
 
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