JPH03238193A - Hard facing method to aluminum alloy base material - Google Patents

Abstract

PURPOSE:To make the improvement in the quality of an overlay layer and the expansion of an application range by placing a facing material consisting of a specific compsn. on an aluminum alloy base material and subjecting the material to building-up under irradiation with a laser. CONSTITUTION:The facing material which is constituted of 10 to 70wt.% chromium, 0.3 to 3 wt.% carbon and the balance iron and unavoidable impurities is placed on the aluminum alloy base material and is irradiated with the laser to form a deposited metal layer. The iron base overlay layer is formed on the aluminum alloy base material in this way. The overlay layer which is high in hardness and heat resistance than the overlay layer of aluminum and copper systems is thus formed. The application range of the overlay hardening of the aluminum alloy parts is widened.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to the hard facing of metals, and more specifically to the hard facing of aluminum alloy substrates.

[Conventional technology]

It is difficult to form a build-up layer (welded metal layer) on the surface of an aluminum alloy base material within the film, and aluminum-based or copper-based metal materials are used as build-up materials. It is difficult to build up on aluminum alloy base materials using metal materials other than these, so overlaying is carried out depending on the application by changing the composition ratio of aluminum-based or copper-based overlay materials. .

[Problem to be solved by the invention]

Aluminum-based overlay materials or copper-based overlay materials have limits in hardness and heat resistance, and cannot be used where high temperatures and wear resistance are required.

It is an object of the present invention to provide a method of forming a hardfacing layer to replace the conventional aluminum-based or copper-based building-up layer.

[Means to solve the problem]

For the above purpose, the following composition Nichrome (Cr): 10~70wt% carbon
(C): 0.3 to 3 wt% iron and unavoidable impurities: The remaining overlay material is placed on the aluminum alloy base material, and a welded metal layer is formed by laser irradiation. Achieved by hardfacing method.

In addition, 30 wt% or less of nickel (N
i), up to 20 wt% cobalt (CO) and 10
Corrosion resistance or wear resistance can be improved by adding at least one of the carbide-forming elements in a wt% or less amount.

[Effect]

The composition of the hardfacing layer according to the present invention is basically iron (Fe
) based metal material and widely adopted TIG
The inventors have discovered that although it is not possible to overlay an aluminum alloy base material using a MIG arc heat source, it is possible to overlay by melting only the overlay material using laser energy. .

The reason why the composition range of the hardfacing layer is defined as described above is as follows.

If the chromium content is less than 10 wt%, overlaying becomes difficult, while if it is more than 70 wt%, bead cracking is likely to occur. The carbon content is 0.3 wt% or less,
When it is diluted (alloyed) with the base material aluminum alloy, the build-up layer becomes brittle, and on the other hand, if it exceeds awt%, bead cracking will occur. Nickel and cobalt are elements that improve corrosion resistance, but if nickel is 30 wt% or more, overlay becomes difficult, and even if cobalt is 20 wt% or more, overlay becomes difficult. Carbide forming elements include tungsten (W), molybdenum (Mo), etc., and improve wear resistance, but if 10 wt% or more is added, overlay is difficult.

In the present invention, it is preferable that the above-mentioned overlay material is prepared as an alloy powder, placed on the surface of an aluminum alloy base material, and scanned and irradiated with a laser under the following conditions to form a weld metal layer (overlay layer).

Laser output ~3.5~10kW Laser beam area: 0.1~5mm2 Overlay formation speed =300~1500mm/min The aluminum alloy of the base material has a relatively low melting point (approx.
~600°C) and melts more easily than the iron-based overlay material (Fe-Cr material, melting point approximately 1300-1400°C) used in the present invention, so heating energy is concentrated only on the overlay material. If necessary, a laser beam is used that can narrow down the area to which heating energy is applied. If the irradiation area, which is the laser beam area, is less than 0.1 mm, the processing area is too small and the build-up time is too long. On the other hand, if it is more than 5 mm2, the energy density will be low and the iron-based build-up material will melt. When the laser power is increased to melt the aluminum alloy base material, thermal energy flows to the base material and melts the aluminum alloy base material.In this case, the alloy forming layer has a particularly high iron concentration. , hard, brittle, and inhomogeneous, which is undesirable.The laser output is 3.5
If the power is less than kW, the overlay formation will be difficult due to insufficient energy input, while if it is more than 10 kW, even the base material will melt and an unfavorable alloy layer will be formed. Furthermore, the build-up formation speed (the length of the formed build-up layer divided by the time) is 300
Below mm/min, productivity is low;
m/min or higher, bead cracking occurs.

[Example] Hereinafter, the present invention will be described in detail by experimental examples including embodiments of the present invention with reference to the accompanying drawings.

Experiment - A large number of molten alloys were made with the components of chromium, carbon, and iron (Fe-Cr-C), and the chromium and carbon contents were as shown in Figure 1, and the alloy was molten by the atomization method. An overlay material was prepared as an alloy powder.

Aluminum alloy castings (A
A plate (C2B: JIS H5202) was prepared, an overlay material of alloy powder was continuously placed on the plate, and a laser was irradiated thereon under the following conditions.

Laser output: 4kW Laser beam area: 0.5mm2 Overlay formation speed: 3 Qrnm/min Laser oscillation width: 6mm Oscillation number: 200Hz The overlay material is melted by laser irradiation to form a welded metal layer (overlay layer). was formed on an aluminum alloy casting plate, and its appearance, hardness, etc. were examined, and the results shown in FIG. 1 were obtained. In FIG. 1, A shows a sample in which overlay was not completed, B shows a sample in which the deposited metal layer was diluted (alloyed) to the cast plate, and C shows a sample in which bead cracking occurred.

A built-up layer was formed at a certain composition ratio of the round bar in the figure, and the hardness (Vickers hardness HV) of each was written above the round bar.

Overlay layer with composition Fe-30Cr-1,5C (HV 374
) with the aluminum alloy casting plate (Xio) as the second
The structure of the built-up layer (X400) is shown in FIG.

Furthermore, while keeping the chromium content (30 wt%) and carbon content (1.5 wt%) constant, nickel was added to 30 wt%.
The structure of the added Fe-30Cr-3ONi-1,5C overlay layer (HV293) is shown in Figure 4.
Figure 5 shows the structure of the built-up layer (HV395.3) of Fe-30Cr-20Co-1,5C with wt% added, and Fe-30Cr-10W with 10 wt% of tungsten added.
The structure of the overlay layer (HV4B5.3) of -1,5C is shown in Fig. 6, and the Fe-
30Cr-10M.

The structure of the 1.5C (7) overlay layer (HV445.7) is shown in FIG. These build-up layers were formed under the conditions described above, and the addition of nickel and cobalt improves corrosion resistance, and the addition of tungsten and molybdenum increases hardness.

A build-up layer was formed on an aluminum alloy casting (AC2B) plate under the laser treatment conditions shown in Table 1 using a build-up material having a main composition of Fe-30Cr-1,5C.

Table 1 Note that the laser oscillation width was 6 mm and the number of oscillations was 200 Hz.

Based on the conditions enclosed by the thick line in Table 1, the laser output,
By changing either the beam area or the overlay formation speed (
For example, only the output was changed, and the beam area and the build-up forming speed were set under the conditions set in the bold lines), and the results are shown in Table 2.

Table 2 Note that ○ in the table indicates good build-up properties, × indicates poor build-up properties, and △ indicates intermediate between these. In the case of *, the laser output was high and alloying with the base material occurred, and in the case of **, bead cracking occurred.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to form an iron-based build-up layer on an aluminum alloy base material, which has much higher hardness and higher heat resistance than conventional aluminum-based or copper-based build-up layers. Because it is a build-up layer, it is possible to build-up and harden aluminum alloy parts that are exposed to high temperatures (for example, aluminum alloy piston skirts, ring grooves, cylinder head seats, etc.) that cannot be handled conventionally.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the alloy composition and the deposited metal layer when a deposited metal layer is formed by laser irradiation using a Fe-Cr-C composition material, and FIG. -30C
FIG. 3 is a micrograph of the metal structure of the Fe-30Cr-1,5C build-up layer; FIG. 4 is a microscopic photograph of the metal structure of the Fe-30Cr-3ONi-1,5C build-up layer, and FIG.
FIG. 6 is a micrograph of the metal structure of the Cr-20Go-1,5C build-up layer, and FIG.
It is a micrograph of the metal structure of the 5C overlay layer, and the seventh
The figure is a micrograph of the metal structure of the Fe-3Fe-30Cr-10,5C build-up layer. A... Sample that cannot be overlaid B... Diluted (alloyed) sample (sample in which the aluminum alloy casting material has been diluted (alloyed) to the weld metal layer) C... Bead cracked sample (X4tJ ( J)

Claims (1)

[Claims] 1. The following composition; Chromium: 10 to 70 wt% Carbon: 0.3 to 3 wt% Iron and unavoidable impurities; The remaining overlay material is placed on the aluminum alloy base material and welded by laser irradiation. A method for hardfacing an aluminum alloy base material, characterized by forming a metal layer. 2. The following composition; Chromium: 10 to 70 wt% Carbon: 0.3 to 3 wt% At least one of 30 wt% or less of nickel, 20 wt% or less of cobalt, and 10 wt% or less of carbide-forming elements; Iron and inevitable impurities; A method for hardfacing an aluminum alloy base material, which comprises placing the remaining overlay material on the aluminum alloy base material and forming a welded metal layer by laser irradiation.