Method of manufacturing composite material by combined melt-spraying

A method of manufacturing a composite material by melt-spraying, comprising the steps of melt-spraying a metal as the main constituent of the composite material onto a base plate and injecting a reinforcing substance comprising discontinuous fibers into the metal melt spray stream upstream of the base plate to effect mixing of the reinforcing substance in the melt-sprayed stream of metal within a temperature range without producing a resultant reaction layer between said metal and said reinforcing substance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method of manufacturing a composite 
material by melt-spraying to manufacture the composite material wherein 
either discontinuous fibers or both discontinuous fibers and grains form 
reinforcing constituents. 
2. Background of the Invention 
In a conventional method of manufacturing a composite material of such 
type, a preformed type is made by coating arranged continuous fibers with 
a melt-sprayed metal as the main constituent of the composite material and 
then forming the tape by hot pressing. In another conventional method of 
manufacturing a composite material of such type, a liner material is melt 
sprayed whose central portion consists of a reinforcing substance and 
whose peripheral portion is made of a metal as the main constituent of the 
composite material. In still another conventional method of manufacturing 
such a composite material, a preformed wire containing discontinuous 
fibers is melt-sprayed. 
In the first mentioned conventional method above, the arranged continuous 
fiber are positioned in front of a melt sprayer including a melt-spray 
gun, and either the gun or continuous fibers are moved relative to the 
other to coat the fibers with the metal to create the preformed tape. A 
prescribed number of such preformed tapes are then piled together and hot 
pressed to increase their density or increase the tightness of the tapes 
at their boundary. 
In the conventional method wherein a wire containing the discontinuous 
fibers is used, the wire is a preformed wire previously made as a 
composite substance or is a two-layer wire whose central portion includes 
the discontinuous fibers and whose peripheral portion is a metal forming 
the main constituent of the composite material. The wire is directly made 
as a composite material reinforced by the discontinuous fibers. Secondary 
processing such as high-temperature extrusion is performed in order not 
only to increase the density of the composite material and its tightness 
at the boundary between the metal and the discontinuous fibers but also to 
enhance the reliability of the material. 
In the first mentioned conventional method above, the continuous fibers 
need to be arranged to an appropriate thickness and width so that a 
uniform metal coating layer can be formed around the fibers. For that 
reason, the speed of manufacture is very slow. Further, this method cannot 
be applied to discontinuous fibers because it is impossible to prevent the 
fibers from scattering. 
In the other conventional method wherein discontinuous fibers are used, the 
fibers are subject to high temperature simultaneously with the melting of 
the metal because the reinforcing discontinuous fibers are passed through 
the melt-spray gun. For this reason, the fibers are damaged or molten and 
gather so that the effectiveness of reinforcement by the fibers is greatly 
reduced. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a method of 
manufacturing a composite material employing discontinuous fibers as a 
reinforcing constituent, in which the efficiency of the manufacturing is 
high, in which the fibers are preheated and wherein the temperature of 
preheating is controlled in order to ensure that the fibers contained in 
the composite material are neither deteriorated nor gathered. In this 
invention, the volume ratio of the reinforcing fibers can be altered with 
the lapse of time or the content of a metal as the main constituent of the 
composite material can be altered with the lapse of time by using a 
plurality of melt-spraying lines, in order to effectively strengthen a 
desired portion of the composite material. 
In the composite material manufacturing method of the present invention, 
the metal and the discontinuous fibers are sprayed from different lines so 
that the volume ratio of the fibers can be altered in the direction of 
piling of the metal and the fibers and the composition of an alloy of such 
metals can be altered in the direction of piling. The efficiency of the 
reinforcement by the fibers and the efficiency of the manufacturing of the 
composite material can be made high without deteriorating or gathering the 
reinforcing discontinuous fibers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment of the present invention is now described with reference to 
FIG. 1 which shows a base plate 1, a melt spraying means or melt-spray gun 
2 for melt-spraying a wire 3 as a main-constituent metal onto the base 
plate 1 by fuel gas or compressed air. An ejection means 4 ejects 
discontinuous fibers as a reinforcing substance together with comprssed 
air into the melt-sprayed metal flow wherein the discontinuous fibers are 
mixed into the melt-sprayed wire 3. A composite material 6 is thus formed 
on the base plate 1. The wire 3 to be melt-sprayed may be made of an 
aluminum alloy containing 6% of silicon. Acetylene as fuel and oxygen may 
be used. The fed quantity of all the gas including the compressed air 
feeding the discontinuous fibers is about 900 liters/min. Silicon carbide 
whiskers of 1 micrometer or less in diameter and 30 micrometers in average 
fiber length are fed as the discontinuous fibers from a hopper (not shown) 
by using compressed air as a carrier gas. The ejection means 4 may compose 
a powder gas melt-spray gun to eject the discontinuous fibers by 
compressed air at about 850 liters/min. to inject them into the flow 
stream 5 of the melt-sprayed metal. The composite material 6 wherein the 
discontinuous fibers as a reinforcing substance are dispersed in the metal 
as the main constituent of the composite material piles on the base plate 
1 is located in front of the melt-spraying means 2 and the ejection means 
4. The rate of the piling is about 30 mm/min. If the distance between the 
base plate 1 and the means 2 and 4 is 250 mm. The volume ratio of the 
fibers piled together with the metal on the base plate 1 is nearly 
constant, whether the fibers are placed in the peripheral portion or 
central portion of the composite material 6 and whether the fibers are fed 
into metal flow stream 5 at the initial stage or final stage of the 
piling. 
The piled composite material 6 is removed from the base plate 1 and then 
shaped to an arbitrary form. The composite material 6 can be extruded at a 
high temperature of 550.degree. C. to provide the reinforcing fibers with 
an orientation to enhance the efficiency of the reinforcement of the 
composite material 6 simultaneously with the shaping of the material. 
In this embodiment, the reinforcing discontinuous fibers are not molten and 
gathered, so that each of the fibers does not lose its original form. When 
the fibers come into contact with the metal, the temperature of the fibers 
is not raised high enough to deteriorate the fibers. The period of time 
during which the fibers are at a relatively high temperature is short. As 
a result, the strength of the reinforcing fibers is not reduced and a 
brittle resultant reaction layer is not produced between the metal and 
each of the fibers. In that respect, the method provided according to the 
present invention differs from a composite material manufacturing method 
in which fibers are dipped in molten metal. Since the composite material 6 
is reinforced by the discontinuous fibers, the secondary processing 
property of the material 6 is excellent. For example, the fibers can be 
oriented in an axial direction simultaneously with such formation of the 
composite material 6 as a high-temperature extrusion. Furthermore, the 
efficiency of manufacturing of the composite material 6 is high. 
FIG. 2 shows another embodiment of the present invention. The same numerals 
in FIG. 2 as those used in FIG. 2 denote the same element or equivalent 
elements, and a detailed description of this embodiment is omitted. The 
compressed air for carrying the discontinuous fibers is not preheated in 
the embodiment shown in FIG. 1, while such compressed air is preheated in 
the embodiment FIG. 2, to enhance the tightness or bond between the metal 
and each of discontinuous fibers in the embodiment shown in FIG. 2. If the 
temperature of the fibers and that of the fiber ejection gas are low at 
the time of the contact of the metal and the fibers in the melt-sprayed 
flow 5 of the metal, especially when the metal has a high thermal 
conductivity and a high melting point, some measures need to be taken to 
enhance the tightness between the metal and the fiber. For example, when 
pure aluminum and potassium titanate fiber of 1 micrometer or less in 
diameter and 30 micrometers in average fiber length are used as the metal 
and discontinuous fibers, respectively, the method of the embodiment shown 
in FIG. 2 is effective to enhance the tightness of the bond between the 
fibers and the metal. The method is also effective in enchancing the 
tightness when a nickel alloy and silicon carbide whiskers are used as the 
metal and the discontinuous fibers respectively. 
FIGS. 3 and 4 show still other embodiments of the present invention. In 
these drawings, an introducing port 30 effects introducing discontinuous 
fibers via a carrier gas into metal melt stream 5. Further a tubular guide 
cylinder 40 improve the yield of the discontinuous fiber. The embodiments 
shown in FIGS. 3 and 4 are simple methods in which a wire gas melt-spray 
gun 2 is used only for ejecting a metal, and nitrogen gas or compressed 
air is used to inject the reinforcing discontinuous fibers into metal 
stream 5. In each of the embodiments shown in FIGS. 3 and 4, four 
introducing ports 30 are provided and the flow rate of the carrier gas is 
about 50 liters/min. The introducing ports 30 are placed in the 
melt-sprayed flow steam 5 of the metal so as to more uniformly disperse 
the fibers. The positions of the ports 30 are determined depending on the 
speed of ejection of the fiber or the flow rate of the carrier gas. If the 
fibers are ejected into the melt-sprayed flow 5 from outside the flow, the 
yield of the fibers contained in a composite material made of the metal 
and the fibers is greatly reduced. 
In the embodiment shown in FIG. 4, a guide cylinder 40 is used in order to 
preheat the carrier gas for introducing the fibers into the melt-sprayed 
flow 5 and improve the yield of the metal and the fibers. The base plate 1 
is moved vertically or moved in the X and Y directions to effect piled 
composite material over a large area, which material is subjected to 
secondary processing such as rolling. 
FIGS. 5 and 6 show still other embodiments of the present invention. 
In the embodiment shown in FIG. 5, a powdered mixture comprising 6% of 
silicon and the rest of aluminum and another powdered mixture comprising 
2% of copper, 0.7% of magnesium and the rest of aluminum constitute a 
first and a second metals, and two powder gas melt-spray guns 2 and 2' are 
used for melts spraying the respective metals. A powder gas melt-spray gun 
4 ejects reinforcing fibers while preheating the fibers and air. 
Therefore, three melt-spray guns are used in all. The quantity of the 
first metal is increased at the initial and final stages of the 
manufacturing of a composite material, while the quantity of the second 
metal is gradually increased in the middle stage of the manufacturing. The 
manufactured composite material is forged at a high temperature of 
550.degree. C. The top and bottom layer of the composite material so 
formed during spray pile up is made of a metal of high resistance to wear, 
while the middle layer of the material is made of a metal which ages at 
room temperature and has a high strength. In this embodiment, the volume 
ratio of the reinforcing fibers is not altered. However, the volume ratio 
can be altered if desired. Reinforcing fibers, reinforcing grains and a 
metal can also be ejected respectively from three melt-spraying lines to 
manufacture a composite material reinforced by both the fibers and the 
grains. 
In the embodiment shown in FIG. 6, two melt-spray guns 2 and 4 are used, 
and a bent conveying/diverging guide 40 is provided in order to enhance 
the yield of reinforcing fibers. Besides melt-spraying shown in FIG. 6, 
arc melt-sraying or plasma melt-spraying can be performed to supply a 
metal as the main constituent of the composite material. When plasma 
melt-spraying, a ceramic can be substituted instead of the metal to 
manufacture a fiber-reinforced ceramic. 
According to the present invention, the discontinuous fibers are not passed 
through the very high temperature portion of melt-spraying system. A 
separate means is used to introduce the fibers, or a melt-spraying means 
is used for preheating the fibers and the gas or a melt-spraying means 
basically imports only kinetic energy to the fibers in order not only to 
eject the fibers but also to melt-spray the metal. As a result, a 
composite material is created in which the reinforcing descontinuous 
fibers are not deteriorated or gathered. The volume ratio of the fibers 
can be altered during piling up of the fibers and the metal. A plurality 
of melt-spraying means can be used so that the composition of an alloy of 
melt-sprayed metals can be altered during direction piling up the metal 
and discontinuous fibers. 
According to the present invention, reinforcing fibers are ejected from a 
line different from that for a metal, so that the mixing of the metal and 
the fibers is completed in a short time and a brittle resultant reaction 
layer is prevented from being produced. The mixing of the fiber will the 
metal melt is performed at such a temperature that the reinforcing fibers 
are not deteriorated or rendered molten and gathered in the melt-sprayed 
flow stream of the metal. A composite material is thus easily manufactured 
from the metal and the reinforcing fibers. A metal alloy can be formed and 
the volume ratio of reinforcing fibers to metal and the composition of the 
metal alloy can be altered during piling up of the metal and the fibers. 
Further the composite material can be secondarily processed after spray 
deposition.