Coating processes – Spray coating utilizing flame or plasma heat
Reexamination Certificate
2003-04-02
2004-10-26
Bareford, Katherine A. (Department: 1762)
Coating processes
Spray coating utilizing flame or plasma heat
C427S453000, C427S455000, C427S456000
Reexamination Certificate
active
06808755
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thermal spraying method for increasing adhesion strength of the thermal sprayed layer. The present invention relates to a thermal spraying apparatus and a powder passage apparatus which can be used in the thermal spraying method.
BACKGROUND ART
There has been developed a thermal spraying method for forming thermal sprayed layer in the industrial world. In the thermal spraying method, material having a powder shape is heated in high temperatures, the heated material is sprayed and is piled up on a surface of an object by thermal spraying. The thermal spraying advantageously increases abrasion resistance and corrosion resistance of the object by the thermal sprayed layer. Also, Japanese Unexamined Patent Publications 63-66900 and 5-5893 disclose a thermal spraying method which uses: an energy source for flying material; and another energy source for heating the material by a laser beam and being independent of the energy source. According to this Publication techniques, the material for thermal spraying flys to the object, and the flying material is heated by the laser beam running parallel with the surface of the object.
In the conventional thermal spraying method, the heated material for thermal spraying decreases in flying speed as it approaches the object. Also, in the thermal spraying method concerning the above-mentioned Publications, the heated material for thermal spraying decreases in flying speed as it approaches the object. Therefore, the thermal spraying layer is not much improved in adhesion strength, even when other spraying conditions are improved.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the aforementioned circumstances. It is therefore an aim of the present invention to provide a thermal spraying method for improving adhesion strength of a thermal sprayed layer. It is therefore another aim of the present invention to provide a thermal spraying apparatus for using the present invention method and for improving adhesion strength of a thermal sprayed layer. Also, it is therefore still another aim of the present invention to provide a powder passage apparatus which can be used in carrying out the present invention method and can suppress powder material from being stopped in a passage.
According to a first aspect of the present invention, a thermal spraying method for producing a thermal sprayed layer by heating material for thermal spraying, by flying the heated material or the heating material to a surface of an object, and by piling the heated material on the surface of the object, comprises the steps of:
(1) preparing a speed-increasing means for adding energy to the heated material or the heating material to increase a flying speed of the material; and
(2) adding energy to the heated material or the heating material by the speed-increasing means in such a manner that a flying speed of the heated material or the heating material increases until the material reaches the surface of the object.
According to a second aspect of the present invention, a thermal spraying apparatus for producing a thermal sprayed layer by heating material for thermal spraying, by flying the heated material or the heating material to a surface of an object, and by piling the heated material on the surface of the object, comprises:
(1) a passage-forming member for forming a passage through which material for thermal spraying passes;
(2) a heating means for heating the material passing through the passage-forming member or discharged from the passage-forming member; and
(3) a speed-increasing means for increasing a flying speed of heated material.
According to a third aspect of the present invention, a powder passage apparatus comprises:
(1) a conductive coil having conductivity, and having an axis and a plurality of loops disposed substantially coaxially with respect to the axis; and
(2) a passage-forming member disposed along the axis of the conductive coil for supplying material for thermal spraying.
According to the first aspect of the present invention, until the heated material reaches the surface of the object, energy is added to the heated material or the heating material by the speed-increasing means in such a manner that a flying speed of the heated material increases. Accordingly, the material for thermal spraying collides against the object at a high speed. So, the thermal sprayed layer is improved in adhesion strength.
Also, in a preferable mode, the flying speed of the material is increased in comparison with that of heating position. In other words, in a preferable mode, the flying speed of the material at the heating position, namely, the flying speed before the acceleration, is lower than that of the material after the acceleration. This mode can lengthen the time for heating the material for thermal spraying, thereby enhancing ability for heating the material for thermal spraying to high temperatures.
According to the second aspect of the present invention, a thermal spraying apparatus comprises: (1) a passage-forming member for forming a passage through which material for thermal spraying passes; (2) a heating means for heating the material passing through the passage-forming member or discharged from the passage-forming member; and (3) a speed-increasing means for increasing a flying speed of material. So, the thermal spraying apparatus according to the second aspect can be used in carrying out the first aspect of the present invention, thermal spraying method. Accordingly, the material for thermal spraying collides against the object at a high speed, and the thermal sprayed layer is improved in adhesion strength. Preferably, the speed-increasing means increases the flying speed of the material than that of the material during heating.
According to the third aspect of the present invention, the powder passage apparatus comprises: a conductive coil, having conductivity, and having an axis and a plurality of loops disposed substantially coaxially with respect to the axis. Also, the passage-forming member is disposed along the axis of the conductive coil. So, the apparatus according to the third aspect can be used in heating the material for thermal spraying by means of induction heating. Induction heating is advantageous in heating the material for thermal spraying in a short time, and in controlling heating temperature.
Further, according to the third aspect of the present invention, when electricity is supplied to the conductive coil, it is suppressed that the material for thermal spraying adheres to the inner surface of the passage of the passage-forming member. The reason is as follows: The conductive coil generates magnetic force along the central axis line of the passage, namely, along the central axis line of the conductive coil. So, the powder material for thermal spraying, having permeability, easily flows along the center portion in a radial direction of the passage.
PREFERABLE MODE OF THE INVENTION
According to the first aspect of the present invention, until the heated material reaches the surface of the object, energy is added to the flying material by a speed-increasing means in such a manner that a flying speed of the material increases. When the flying speed of the material for thermal spraying is increased, the material collides against the object at a high speed, adhesion of the material is improved, and the thermal sprayed layer is improved in adhesion strength.
According to the preferable mode of this invention, the adding of the energy for increasing the flying speed of material is carried out after the heating of the material. That is to say, after the material for thermal spraying is heated, the flying speed of the material is increased. The heating before increasing the flying speed of the material can lengthen the time which is required for heating the material.
Or, according to the thermal spraying method for concerning another preferable mode of the first invention, the flying speed of the material can be increased during the heating of material. Also, the
Kodama Kouta
Marumoto Ikuo
Miyamoto Noritaka
Bareford Katherine A.
Toyota Jidosha & Kabushiki Kaisha
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