JPH03202448A - Surface modifying method by laser beam - Google Patents

Abstract

PURPOSE:To obtain the surface of a base metal having excellent wear resistance, heat resistance, corrosion resistance, etc., by melting a wire obtd. by incorporating prescribed amounts of inorganic hard particles having specified value or above of hardness Hv into an Al(alloy) matrix by a laser beam and forming a film on the surface of a base metal. CONSTITUTION:A wire obtd. by incorporating hard particles constituted of ceramics, intermetallic compounds, cermet, metals or the like, having >=500Hv hardness in itself and having <=500mum particle size into a matrix of Al or an Al alloy by <=50vol.% is prepd. The diameter of the wire is preferably regulated to <=3.2mm, and moreover, the wire having a rectangular section is preferable. Then, the wire is melted by a laser (a CO2 laser beam is suitably used) to form a film on the surface of a base metal of Al or the like. In this way, the film having the above-mentioned properties, which is furthermore homogeneous and excellent in adhesion for the base metal even at a high temp. can be obtd.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to surface modification technology using laser. More specifically, the present invention relates to a method of melting a wire using a laser and adhering it to the surface of a base material to form a film with excellent properties such as wear resistance, heat resistance, and corrosion resistance. (Prior art and problems to be solved) Conventionally, there are surface treatment methods that form films with various characteristics on the surface of a base material, which is a metal material, to impart properties different from those of the base material. Depending on the material of the base material, various methods such as ion implantation, surface hardening, hard plating, nitriding, diffusion/penetration plating, texture, thermal spraying, etc. are appropriately selected and adopted. For example, when aluminum or its alloy is used as a base material to take advantage of its light weight, methods for hardening the surface include different materials such as W-based, Ni-based, Co-based, 5i-F, etc.
There is a method of forming a thin film by touch, thermal spraying, etc. using e-based materials. for example. Regarding the method by overlaying, see JP-A-58-179569, JP-A-58-215291, JP-A-61-115676, etc. Regarding the method by thermal spraying, JP-A-54-701
No. 2, No. 54-7013. No. 63-4051 and the like can be mentioned. However, thin film materials have a different coefficient of thermal expansion than aluminum materials,
There were problems such as poor adhesion, the need for many expensive materials, large differences in specific gravity, and the tendency to segregate during thin film formation, particularly during overlaying, making it impossible to obtain homogeneity. In addition, attempts have been made to make such thin films into multilayer films and layer them in order of the thermal expansion coefficient of the base material to alleviate the difference in thermal expansion coefficient with the base material, but in addition to the above problems, the process is There were problems such as complexity. On the other hand, if you want to obtain a film with a film thickness on the order of millimeters. Although there are methods for attaching ceramics to the surface of aluminum materials, most methods involve spreading ceramics on the base material in advance and then melting and attaching them using arcs, lasers, etc.
Many lack practicality. In particular, surface modification technology using lasers has been attracting attention, but although it has the potential to add new functions and improve efficiency,
The current situation is that it has not yet reached the stage of practical application. The present invention has been made in view of the above circumstances, and
By improving surface modification technology using laser, we can efficiently and stably form coatings that have excellent adhesion to the base material and have desired properties such as wear resistance, heat resistance, and corrosion resistance. The purpose is to provide a method that can be used to (Means for Solving the Problems) In order to achieve the above object, the present inventors first conducted intensive research to find out the cause of the above problems when thermal spraying and overlaying are employed as coating formation methods. As a result, in the conventional surface treatment method by overlaying or thermal spraying, hard particles are supplied as they are, that is, in the form of particles or powder, onto the surface of the base material and melted to form a film. It turns out that there are rate issues. Therefore, as a result of further research on measures to minimize the difference in thermal expansion coefficient with the base material while using hard particles, we developed a wire for forming a surface film and proposed it earlier (Patent Application No. -19
No. 9626). However, as a result of further research on the usage of this wire, it was found that by applying surface modification technology using laser, a surface film with excellent characteristics could be obtained by combining the effect of using laser. The present invention was made based on this knowledge. That is, in the surface modification method using a laser according to the present invention, hard particles made of ceramics, intermetallic compounds, cermets, metals, etc. and having a hardness Hv of 500 or more are added to an aluminum or aluminum alloy matrix in an amount of 50 vol%. Using the wire contained below,
This is characterized in that it is melted with a laser to form a film on the surface of the base material. The present invention will be explained in more detail below. (Function) As mentioned above, in the past, the material of the base material and the material of the film to be formed were generally selected almost independently, and a film made of different materials was formed on the surface of the base material. So,
Considering that the base material to be coated is mainly aluminum or an aluminum alloy, a matrix made of aluminum or an aluminum alloy of the same type as this is coated, and at that time, predetermined hard particles are contained in the matrix. We developed and provided a wire based on the following. This makes it possible to obtain a film with excellent adhesion even at high temperatures. Of course, since the wire contains hard particles, a coating with high hardness can be obtained, and furthermore, if the matrix of the wire is an age-hardening aluminum alloy, the effect of improving the hardness of the coating due to age hardening is also expected. Yes (see Figure 1)
. Furthermore, in the present invention, we focused on the high efficiency and rapid heating and quenching action that are features of lasers, particularly on quenching, and found that this action, in combination with the material of the wire, allows a film with excellent properties to be obtained. That is, the wire is melted by the laser and attached to the surface of the base material, but the faster the quenching rate is, the more the coating is burned. Good hardening means that the hardness of the coating increases (due to the aging precipitation hardening effect after laser spraying).
At the same time, the crystal grains become smaller, and the smaller the crystal grains, the smaller the spacing between dendrites, resulting in the effect of less segregation. As described above, according to the present invention, 1) the effects of using a wire with a specific configuration (adhesion, film hardness), and 2) the effects of using a laser (aging precipitation hardening and segregation reduction due to solution quenching of the film) can be expected to be synergistic. Next, processing conditions of the present invention will be explained. The hard particles can be made of various materials such as ceramics, intermetallic compounds, cermets, metals, etc. These include AR, Zr, Cr, and Ti. V, Ta, Si, W, Nb, Cu, Ni, Co, Fe. [N]] and C as a base element. For example, examples of ceramics include alumina, titania, alumina titania, and the like. Examples of composite powders, nitrides, and borides include Cr, C2, TiC,
B4C,WC,ZrC1TfB,,MoB,,ZrB,
, TiN, ZrTi, and composite powders thereof. Of course, it goes without saying that it is not limited to only these. In addition, when selecting these hard particles, it is preferable to select them in relation to the material of the base material. That is, if a material having a specific gravity as close as possible to that of the base material is selected in particular, segregation during film formation can be significantly reduced and uniformity of the film can be ensured. For example, if the base material is aluminum, the specific gravity of aluminum is 2.7.
Considering that, those having a specific gravity of about 2.7±2, such as Si, Al, O, SiC, Si, N,
, B, C, CBN, BN-TiB, etc. Pay particular attention to this when overlaying. Of course, it goes without saying that the material of the hard particles can be selected depending on the characteristics of the film to be formed6.For example, when the purpose is to harden aluminum, WC,
Mo, ZrO2, TiC, TiN, Cr, C2, Cr,
ZrO, -Y, 03, WC-Ni-Cr, WC-Co1
MgO, TiC-Ni, NbC, etc. may be selected. However, the hard particles themselves must have a hardness Hv (Knoop hardness) of Hv≧500, and must be included in the matrix in an amount of 50 vol% or less. Although it depends on the material of the hard particles, it is usually 10 to 40 vol%. Particles with a hardness Hv lower than 500 cannot provide wear resistance, which is the main coating property. If the content exceeds 50 vol%, it becomes difficult to homogeneously disperse the hard particles in the matrix of the film, or there are problems such as poor compatibility with the base material because the matrix decreases. Furthermore, such hard particles have a diameter of 5
It is recommended that the size be 00 μm or less. Sizes larger than 500 microns make it difficult to homogeneously disperse the hard particles in the matrix. However, if it is too thin, it will easily melt during laser treatment and it will be difficult to obtain a film, so it is preferable to use a material with a diameter of 1 μm or more, and a shape that does not have sharp protrusions (e.g., spherical).
It is preferable for manufacturing purposes. The matrix consists of aluminum or an aluminum alloy, but various compositions and compositions are possible. In addition to pure aluminum (i o o o type), AQ-M
n series (3000th), AM-5i series (4000th), A
Non-aging aluminum alloys such as Lazy-Mg series (No. 5000), AQ-Cu-Mg series (No. 2000), A-M
g-8i series (No. 6000), AM-Zn-Mg series (70
Examples include aging type aluminum alloys such as No. 00). The form of the wire made of a matrix and hard particles is not particularly limited, but it may be a solid wire in which hard particles are dispersed in a matrix, or a composite wire in which the matrix is used as a hoop and hard particles are filled inside. There are various aspects. Solid wires are made into billets or slabs by powder metallurgy, in which matrix powder and hard particles are mixed and solidified, or by molten metal forging, in which matrix molten metal is impregnated under pressure into a preform of hard particles. , formed into a wire, or obtained by hydrostatic extrusion. In the case of a composite wire, the cross-sectional shape is a hoop filled with hard particles, but depending on the case, a heat generating agent or a heat insulating agent (Mg, aluminum powder, REM type, etc.) can also be filled. By filling the film with a heating agent, the effect of preheating or keeping warm after film formation can be obtained, and the adhesion can be improved. Note that in order to obtain a heat retention effect, it is also possible to cover the surface with a slag agent after film formation. Next, laser spraying will be explained. As shown in FIG. 2, the wire is melted by a laser to form a film of desired thickness and characteristics on the surface of the base material. The film can have a variety of thicknesses, and can be uniformly formed from a micron order to a millimeter order thick film. The laser spraying conditions may be almost the same as those for laser welding. However, it is preferable to form the film over a wide area. For example, it is advantageous for the wire diameter to be small in order to prevent segregation, and a wire with a diameter of 3.2 mm or less is desirable, and a wire with a rectangular cross section is desirable. Various types of lasers are possible, such as gas lasers (eg, CO lasers), solid lasers (eg, YAG lasers), and CO lasers are suitable. Beam modes and outputs include single mode, multimode, ring mode, etc., but ring mode or single mode is preferable for film formation.The focusing method is when the focus setting position is on the base material and when the focus setting position is on the base material. Although there are cases where it is above, the latter is preferable for film formation because it has a wider bead width and a shallower penetration depth. A faster beam traveling speed is preferable because the penetration depth is shallower and the hardening effect is greater. (Example) Next, an example of the present invention will be shown. Pure aluminum was used as a wire base (matrix) for aborted carp, and wires containing particles of the size and blending amount shown in Table 1 were prepared. Two types of wire were used: a solid wire with particles dispersed therein, and a composite wire with particles filled in a hoop made of a wire base. Next, laser spraying is performed using these wires,
A film having the thickness shown in Table 1 was formed on the surface of an aluminum base material (A5083). The laser spraying conditions were CO, laser, output 5 kW, and running speed 50 cm/win. For comparison, gas spraying was performed instead of laser spraying. A wear resistance test was conducted on the obtained film under the following conditions, and the amount of wear was measured. The results are also listed in Table 1. Wear resistance test conditions〉 Test method Ni-Okoshi test method Final load: 3 kgf Wear rate: 1,36 m/sec Wear distance: 100 m From Table 1, among the tests Nα1 to 9, when gas spraying (comparative example) was used All have a small amount of wear and have good wear resistance regardless of the film thickness, but laser spraying (example of the present invention)
It is clear that the amount of wear is even smaller in the case of gas spraying, and that the wear resistance is excellent.

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Figure 3 shows the relationship between the final load and the amount of wear for the thermally sprayed coating obtained using the wire in Test No. 3. From the same figure, the gas sprayed coating obtained with &3 wire (comparative example) has less wear regardless of the final load and has stable and good wear resistance (high However, the laser sprayed coating (example of the present invention) shows even better wear resistance than the gas sprayed coating. Note that large pores are generated in the sprayed coating obtained with a wire (solid wire) made only of 5183, and the amount of wear is large. In Example 1, an age-hardening aluminum alloy (AQ-Cu-based,
A laser sprayed coating was formed under the same conditions except that AQ-Mg-Si type) was used. Table 2 shows the results of measuring the amount of wear on the resulting coatings. Note that the amount of wear is a value measured 120 hours after laser spraying. From Table 2, it can be seen that the amount of wear was smaller than in Example 1, and the wear resistance could be further improved.

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・Wire, 5... Base material, 6...Thermal spray coating.

Claims (4)

[Claims] (1) Using a wire in which hard particles made of ceramics, intermetallic compounds, cermets, metals, etc. and having a hardness Hv of 500 or more are contained in an aluminum or aluminum alloy matrix in an amount of 50 vol% or less, A surface modification method using a laser, which is characterized by forming a film on the surface of a base material by melting it with a laser. (2) The method according to claim 1, wherein the hard particles have a diameter of 500 μm or less. (3) The hard particles include Al, Zr, Cr, Ti,
V, Ta, Si, W, Nb, Cu, Ni, Co, Fe,
Claim 1 or 2 using a compound or metal whose base element is at least one selected from the group consisting of Ni and C.
The method described in. (4) The wire is either a solid wire in which hard particles are dispersed in an aluminum or aluminum alloy matrix, or a composite wire in which the hard particles are filled in an aluminum or aluminum alloy sheath metal serving as a matrix. The method according to item 1, 2 or 3.