JPS6011094B2 - Surface alloying method for steel or cast iron - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming surface layer casings on objects, particularly for surface alloying of steel or cast iron.

Many techniques have been used since ancient times to improve the resistance of engineered or semi-engineered metals (including elemental, alloys and compounds) to abrasion, abrasion, deformation, corrosion, heating and/or erosion. method is implemented.

These methods include carburizing, nitriding, silicification, diffusion hardening,
The surface of the metal is coated by methods such as hardfacing (deposition of a high alloy layer onto the surface), flame hardening, induction hardening and physical modification (e.g. peening) to improve the composition and/or microstructure of the surface. modifi
cation).

Coating methods include electroplating of chromium or nickel onto the surface, plasma light or flame fogging of refractories onto the surface, and roll cladding (for sheet or wire rolled products). It is an important object of the present invention to improve known methods of forming surface layer casings on objects to provide better casing products.

Another object of the invention is to form a surface layer on a substrate in a significant proportion of the substrate as an independent and distinct phase.
and/or converting the newly formed compound into a form containing it as a composition. Another object of the invention is to
The purpose is to transform the surface layer on the substrate into a casing shape by alloying and/or melting and mixing the surface layer with a reactive substance in a short time. According to the present invention, a coating layer of one or more alloying components is applied to the surface of steel or cast iron, and then a coating layer is formed along a linear machining path on the surface of the coating layer at a predetermined depth. A process for surface alloying steel or cast iron, which consists in traversing the steel or cast iron immediately below the coating layer with a laser output beam along the linear machining path so as to melt, mix, and resolidify the surface of the steel or cast iron. In order to improve the mixing of the coating layer with the underlying steel or cast iron, the laser beam is deflected to successively scan the coating surface along a number of linear machining paths arranged in parallel relationship and While traversing the layer, the laser beam is vibrated laterally in its multi-linear processing path, and the laser beam is a continuous wave laser output beam and has a power output of 7.75-1550 KW/sq. inch) power density and 1
A method for surface alloying metals is provided having a linear scan rate of 2.7 to 127 skins/min (5 to 50 inches/min).

According to the invention there is also provided a casing product manufactured by carrying out the above method.

In carrying out the method, the substrate portion may be coated with a minor component to form an intimate mixture and/or compound therewith, which is intended to be introduced into a predetermined surface layer depth of the substrate; The substrate material in the layer should occupy a major volume percentage in the mixture, preferably 1019% by volume. The coating may contain other supplementary sources of minor components (
You can also add
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Preferably 0.065 to 2.58 square meters (0.01 to 0
．． Applying a concentrated beam of radiant energy to a surface area limited to a surface area of 4 inches square or less and scanning the radiant energy beam relative to the surface to sequentially melt and re-melt a series of such areas. The surface layer of the substrate is melted to a predetermined depth by solidifying and defining the desired surface improvement pattern.

It is preferred to control melting conditions to permit such mixing to the extent that mass transfer by forced mixing of the coating material and molten substrate material predominates over diffusion in the fused surface layer region. Any such region is kept in a molten state for less than 1 second, preferably less than 1 second, and the substrate imparts a very large heatsink to the molten region, resulting in the removal of impinging energy rays. Guarantees rapid solidification.

The process is preferably carried out at atmospheric pressure or under pressure to reduce vaporization of the mixed components and to avoid the time required for vacuum fixtming, cleaning and assembly.

Temporary vessels applying melting energy to further promote mixing of ingredients.
e) is preferably locally vibrated at 100 to 1000 hertz.

Such vibrations locally perturb the radiant energy beam (s
weeping) and/or switching the contour of the energy line, for example between rectangular and circular shapes. These objects, features and advantages of the present invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings.

In FIG. 1, a base metal part 10 is shown, which can be a rolled product, such as a steel sheet, or a workpiece, such as a steel valve seat.

In order to increase the wear resistance of the top surface, a layer of minor components (eg chromium and manganese) is coated on top of this to transform the surface of this part into a high alloy composition. A predetermined depth line 16 is established below the surface of the component 10 to define the surface layer and amount of base metal that will form the minor component coating 12 and the desired alloy layer. Energy absorbing layer 14 can be applied as an underlying coating to coating 12 or mixed with coating 12 onto the substrate portion. A beam of radiant energy 18 is applied from a suitable light source, such as a laser, to create a melting zone 19 up to the depth line 16, and the relative movement of the beam 18 to the base part 10 causes melting to occur linearly or intermittently as desired. The zone is scanned to form a temporal array of such melt zone structures. While the melting zone 19 is maintained in either position, the transfer of heat from here to the large heat reservoir provided by the base part 10 is very rapid and the impinging ray 1
As soon as 8 moves relatively from here, the melting zone cools and solidifies. For the treatment of metals, a 5-2 plate W laser beam (square ca. Approximately 7.75-1550KW per square inch (gives a beam power density of approximately 50-1000 dishes W per square inch)
12.7 to 127 arcs (5-
It is preferred to scan at a speed of 50 inches/minute).

Typical residence times in the molten state for any particular region of the surface layer are between 0.1 and 1.9 mm, with temperatures below the possible solidification temperature for the alloy composition within this range for the molten region. Cooling times are typically 0.1 to 1.9 sand. During melting, thermal gradients alone cause a substantial degree of mixing of minor components of the coating layer with portions of the molten surface layer. Furthermore, it is believed that the high energy input induces pressure waves that promote more intense mixing. Such mixing can be enhanced even more substantially by local oscillations of the impact energy, as discussed below in connection with FIGS. 4 and 5. When the substrate is heated, the scanning speed can be increased.

See Example 7. Referring now to FIG. 2, a base part 10 is shown having a hardened surface layer casing 20 and an interfacial layer 22. As shown in FIG.

The thickness of layer 20 is at a depth that essentially corresponds to predetermined depth line 16 (FIG. 1). Referring now to FIG. 3, the arrangement of equipment for carrying out the invention is shown. Processed piece 1
0' rests on a conventional milling machine base, which is equipped with a device for moving the workpiece in the orthogonal direction, as indicated by the double-headed arrows 11 and 13, and a lateral movement control device. The x and y lateral movements can be simultaneous, or one can be intermittent. Radiant energy beam 18 acting as described above in connection with FIG.
Give it as 0. This laser is US Patent No. 3,721,915
No. 3702973, No. 3577096, and No. 371303. Laser 30 in FIG. 3 is coupled to a beam splitter 31. Laser 30 in FIG. One or more beam tunnels 36 exiting the beam distributor 31 are used to direct the laser beam to one or more application points, and a tiltable mirror mechanism and rotating beam chopper gears are used to direct the laser beam to one or more application points. Rays can be time-divided and even multiplexed between such application points very quickly. A mirror mechanism, shown schematically at 38, is provided for perturbing the beam 18 in addition to or instead of moving the workpiece on the table 39, and for local vibrations as described below in connection with FIG. An adjustable configuration can be provided to receive the laser beam from the optics module.

Now, in FIGS. 4 and 5 (sketches of a workpiece 10 being processed according to the invention using the apparatus of FIG. 3),
The workpiece is coated with a coating (12) as described above in connection with FIG.
14) on it.

This workpiece moves relative to the light beam in the longitudinal scanning direction shown by arrow 11A in FIG. 4 and arrow 11B in FIG. 5, and intermittently moves as shown by arrow 13 in FIGS. to form a series of adjacent lines. ray tunnel 3
6 is connected to an optics module 37, where the laser beam is shaped for heating the substrate.

The beam may be interrupted during the turnback, or alternatively maintained during passage and return to provide an adjacent line (20A in FIG. 4 or 20B in FIG. 5).

This beam can also be interrupted to step over the surface area of the coating (12/14) to form the desired pattern of phosphorized and unhardened areas. The relative movement indicated by both arrows 11A and 11B in FIGS. 4 and 5, respectively, is typically about 50.8 k/min (2
This is done at a relative scanning speed of 0 inches).

However, vibration waveform 1 superimposed on arrow 11B in FIG.
Local vibrations transverse to the scanning direction can be superimposed on the scan of FIG. 5, as shown at 1C. In the first operating method shown in FIG. 4, the size of the acting spot typically corresponds to the entire center of line 20A, and in the second operating method shown in FIG. Substantially smaller, in the second case covering the entire line with the vibration of the spot against the surface of the part 10, but by sweeping the energy input repeatedly over the same surface area portion, the part 1
The mixing of the fused surface layer of 0 and the local fused portion of the coating I2 is substantially promoted. By continuously changing the areal shape of the spot, for example, by switching between a linear shape and a circular shape, or between a circular shape and a star shape, energy is concentrated in a spot shape having the same inside as the line 20B. can also induce such a gradient. In addition to or instead of transverse vibrations of the beam center, longitudinal vibrations can also be used. The invention is further illustrated in the following examples, which are not intended to be limiting.

Example 1 A metal powder mixture was coated onto the surface of a metal article by spraying.

The coated surface was scanned with a Shoko Energy laser beam to melt the surface and the powder and uniformly alloy it. This treatment was found to substantially increase the hardness of the fused zone. In one experiment, the surface of AISICIOI Yokozuna was treated with 0.0006 manganese phosphate using an industrial phosphomanganization method.
It was coated with a layer of 1'4 to 1/2 mil. This optional manganese phosphate coating facilitates laser beam absorption. Other possible heat absorbing materials are zinc phosphate, aluminum oxide, and carbon black. This selection also depends on the wavelength of the heat source. Next, 6 pieces of carbon powder with a particle size of 45 mm, 3 pieces of chromium powder with a particle size of 10 mm, suspended in inpropyl alcohol on a tabletop, and 3 pieces of chromium powder with a particle size of 4 mm were added.
A mixture containing 5 w of manganese powder and 3 w of manganese powder was uniformly sprayed onto the manganese phosphate coating. The thickness of the loosely packed powder metal coating was 0.0013 skin (1/2 mil). The surface of the steel containing this mixture of metal powders was vibrated (
locally vibrated) 11-11. The gruel W laser beam was scanned at 50.8 arc/min (20 in/min). The shape of this laser beam is 0.25 arc x 1.27 arc (0.1
It has a rectangular shape (inch x 0.5 inch) and is longer in the direction perpendicular to the horizontal direction. This is because local vibrations are performed along this direction so as to cover the entire line (20B in FIG. 5). The vibration rate was 690 hertz. Under these conditions, the surface of the steel melted and homogeneously alloyed with carbon, chromium, and manganese powders. The hardness of the melted and resolidified band was greater than Rockwell C mottling up to a depth of 5 mils, while the hardness of the steel was Rockwell B93. FIG. 6 is a 20-fold enlarged micrograph of a processed piece processed according to Example 1, and includes FIGS. 6A, 6B, 6C, and 6D.
The figure shows depths of 0.0051, 0.0076, 0.0102, and 0.0051, respectively, from the surface of the workpiece in the portion shown in FIG.
Scanning electron micrograph magnified to 350 tones of a small portion of the 0127 arc (2, 3, 4, 5 mils).

Turning first to FIG. 6, the unaffected substrate is shown at 10, its alloyed surface layer is shown at 20, and the interfacial layer 22 defines the internal boundary between the surface layer 20 and the substrate 10. is forming.

Layer 20 has a finer grain structure than the substrate. 6th
FIG. 160 shows a two-phase structure in a layer 20 of martensitic dendrites surrounded by carbides in the interphase dendrite region. Figures 7, 8, and 9 are Example 1
Indicates the concentration of minor alloying components for carbon, chromium, and manganese, respectively, in the final product manufactured by the process according to the following.

The curves in FIGS. 7, 8, and 9 plot the concentration of each minor alloying component versus casing depth. These curves were fitted to a single point in the original data according to conventional statistical methods. These curves show an increase in minor components in the iron alloy composition. curve 91 no 9
The dip in the third section (Figure 9) indicates the vaporization of manganese on the surface; if no vaporization occurs, this curved section will be 95
or somewhat higher than this will be indicated by a dashed line. If the casing depth is much larger (Example 7)
), surface effects become less important. FIG. 10 shows the change in hardness of the final product subjected to local vibration laser treatment.

The melting zone was 0.0127 skin (5 mil) deep and within this zone the hardness was Rockwell C58-63, while the hardness value of the thermally affected zone in the steel was Rockwell B90. The hardness value of a portion of the steel core was Rockwell B93. The depth of the thermally affected zone is approximately 0.
It was 127 melons (0.05 inch). Example 2AI
The surface of the SICIO18 plate was coated with 0.0006-0.0013 (1/4-
1/2 mil) was coated with a layer of manganese phosphate.

Particle size 45 suspended in 50' inbropyl alcohol
A small amount of the mixture containing 10 g of aluminum powder was brushed evenly onto the manganese phosphate surface.

Aluminum powder was applied to suppress gas evolution during melting. Next, a mixture containing 12 pieces of carbon powder with a particle size of 45 particles, 6 pieces of chromium powder with a particle size of 10 pieces, and 6 pieces of manganese powder with a particle size of 45 A suspended in 40 pieces of inpropyl alcohol was mixed into an aluminum powder. The coating was evenly sprayed 20 times. The thickness of the loosely filled metal powder coating is 0.03
It was 81-0.0508 mils (15-20 mils). The coated surface was then laser treated in the manner described in FIGS. 4 and 5 above, respectively, on separate samples.

That is, one sample is melted to a certain depth without local vibration, and the minor components of the alloy are mixed with the main component obtained from the base material, and the other sample is melted to a certain depth, and the other sample is melted without local vibration. Hardened. For both modalities, the melting time for a given surface area was 0.3 seconds and the power from the laser was 1311 W. For operation without local vibration, the lateral movement speed is 127 linear inches/min (50 linear inches/min), and for operation with local vibration, the lateral movement speed is 50.8 linear inches/min (
20 inches/min). The average energy density used for melting in both cases was 250-30 dishes W per square inch of workpiece surface area. In non-local vibration operation, the beam shape of the colliding laser beam is 0.64 skin (0.25
In the local vibration operation, the shape of the light beam is 0.25 arc x 1.27 inches long in the direction perpendicular to the horizontal direction because the local vibration is performed in the horizontal direction so as to cover the entire line.
(0.1 inch x 0.5 inch) rectangle (5th
20B in the figure). The vibration rate was 690 hertz. 1st
Figures 1 and 12 show the variation of the minor alloying components of the final product for chromium and manganese, respectively.

The upper curves for chromium and manganese were obtained with local vibration, and the lower curves were obtained without local vibration. Figure 13 shows laser processing without local vibration,
and hardness changes in separate final products subjected to laser treatment with local vibration.

Rockwell C27~ for laser processing without local vibration
giving a hardness value in the range of 44; locally vibrating laser treatment gives a hardness value in the range of Rockwell C46-58;
In both cases this value extended to a depth of approximately 0.076 inches (0.03 inches). The hardness value for the copper core portion was Rockwell B93, and the hardness value for the heat-treated band was Rockwell B90. The depth of the thermally affected zone was approximately 0.05 inches.
Example 3 The surface of AISICIO18 plate was treated with 0.0006 to 0.0013 N (1/
A layer of manganese phosphate (4 to 1'2 mil) was coated.

On the surface of this manganese phosphate, 1 part of aluminum powder with a particle size of 45 mm suspended in 50 parts of inpropyl alcohol was applied.
A small amount of the mixture was evenly brushed on. This aluminum powder coating was applied over the manganese phosphate coating to prevent gas evolution during melting. Next, 12 pieces of carbon powder with a particle size of 45 mm suspended in 40 mm of inpropyl alcohol, 2M of chromium powder with a particle size of 10 mm, and 2M of chromium powder with a particle size of 45 mm
A mixture containing 80% of French tungsten powder was spread evenly onto the aluminum powder coating in a 2 m cluster. The thickness of the loosely filled metal powder coating is 0.0635-0.0762
It was an enemy (25-30 mil). The surface of the steel containing the mixture of metal powders was treated with a locally oscillating laser beam of 1 pine W at 25.4 mm.
Scanning was performed at 10 inches/minute. Since the local vibration was carried out in the lateral direction, the shape of the laser beam was 0.2 x 1.27 cm long (0.1 inch x
0.5 inch) rectangular. The vibration rate was 690 hertz. The surface layer of melted and resolidified steel is carbon,
Intimately alloys with chromium, tungsten, and aluminum powders. FIG. 14 shows the hardness change in the final product subjected to the local vibration laser treatment as described above in Example 3.

The molten zone has a depth of 0.1118 (44 mils) and within this zone the hardness is Rockwell C48-53, while the hardness value of the steel core is Rockwell B93 and the thermally affected zone has a hardness of Rockwell C48-53. The hardness value was Rockwell B90. The depth of the thermally affected belt was approximately 0.305 m (0.12 inch). Example 4 The surface of a gray cast iron part containing about 0.2% by weight of chromium was treated with chromium by an industrial manganese phosphate method.
．． A layer of 0006-0.0013 arc (1/4-1/2 mil) was coated with manganese phosphate.

A mixture containing 50% of chromium powder with a particle size of 10" suspended in 40" of inpropyl alcohol was then uniformly exposed on the manganese phosphate coating about 10 times. The thickness of the loosely filled metal powder coating is 0.0013 to 0.0025 mm (
1/2 to 1 mil). The surface of a cast iron part containing chromium powder was scanned with an 11 KW locally oscillating laser beam at 76.2 skins/min (30 inches/min). The shape of the laser beam was a rectangle measuring 0.25 arc x 1.27 arc (0.1 inch x 0.5 inch), and was elongated in a direction perpendicular to the lateral direction because of the local vibration in the lateral direction. The vibration speed is 69
It was 0 hertz. In this way the surface of the cast iron part was melted and intimately alloyed with the chromium powder. Figure 15 shows the concentration of minor alloying components in the final product relative to chromium.

This curve has been fitted to a point (not shown) in the original data according to conventional statistical procedures. This curve shows the increase in chromium concentration within the melt zone at a depth of 0.0254 m (10 mils). FIG. 16 shows the change in hardness in the final product subjected to local vibration laser treatment.

Within the melting zone, the hardness is Rockwell C60-65;
On the other hand, the hardness value of the cast iron parts that were not subjected to laser action was Rockwell B95. The hardness value of the thermally affected zone was Rockwell C56-61. Example 5 The surface of a gray cast iron plate was coated with a layer of 0.0006-0.0013 (1/4-1/2 mil) manganese phosphate by an industrial manganese phosphate process.

Then, a mixture containing 2 chromium powder with a particle size of 10 mm and a silicon powder with a particle size of 45 mm suspended in 40 mm inpropyl alcohol was uniformly spread over the manganese phosphate coating 5 times. It was foggy. The thickness of the loosely filled metal powder coating was 0.0013-0.0025 arc (1/2-1 mil). Cast iron parts containing chromium and silicon powder are placed in furnace 3.
The surface was then scanned with a locally oscillating Fox W laser beam at 152.4 k/min (60 in/min). The shape of the laser beam was 1.27 x 1.27 arc (0.5 inch x 0.5 inch). The vibration velocity is 69 in the direction perpendicular to the lateral direction.
3 Lu to 0, it was 125 Hz along the lateral direction. Under these conditions, the surface of the cast iron part was melted and intimately alloyed with chromium and silicon powder. FIG. 17 shows the change in hardness of the final product subjected to local vibration laser treatment.

The melt zone was approximately 40.0127 mm (5 mils) deep and the hardness within this zone was Rockwell C56-60, while the hardness value of the cast iron parts that were not subjected to laser action was Rockwell B95. The hardness of the thermally affected zone was Rockwell C45. Example 6 Gray cast iron plate was treated with industrial manganese phosphate to 0.00
It was coated with a layer of mantaganese phosphate, 1/4 to 1/2 mil.

Then, it was suspended in 40 ml of inpropyl alcohol.
A mixture containing five particles of chromium powder with a particle size of 10 was uniformly spread on the manganese phosphate coating five times. The thickness of the loosely filled metal powder coating was 0.0013 to 0.0025 skin (1/2 to 1 mil). The surface of a cast iron part containing chromium powder was scanned with a class W locally oscillating laser beam at 76.2 arc/min (30 in/min). The shape of the laser beam was 1.27 cm x 1.27 cm (0.5 inch x 0.5 inch). The vibration rate was 690 tarts perpendicular to the transverse direction and 125 hertz along the transverse direction. Under these conditions, the surface of the cast iron part was melted and intimately alloyed with the chromium powder. FIG. 18 shows the change in hardness in the final product subjected to local vibration laser treatment.

The melt zone was 0.0254° deep (10 mils) and the hardness within this zone was Rockwell C58-67, while the hardness value of the cast iron part that was not laser treated was Rockwell B98. The hardness of the thermally affected zone was Rockwell C51. Example 7 The surface of a mountain SI481 high-grade steel plate was treated with an industrial phosphomanganization method to form a 0.0006 to 0.0013 arc (1/4 to 1'
2 mil) was coated with a layer of manganese phosphate.

Chromium powder with a particle size of 10A was sprinkled uniformly onto the manganese phosphate coating, and the metal powder was compacted. The depth of the tightly compacted chromium powder coating is approximately 0.064 skin (0.0
25 inches). Carbon powder having a particle size of 45 mm was uniformly sprinkled onto the chromium powder coating, and the carbon powder was compacted. The depth of the densely compacted carbon powder coating is approximately 0.0
It was 25 feet (0.01 inch). The steel plate containing this carbon and chromium powder was heated to 482.2℃ (9000F).
), then 1.96〆/hour (7 cubic feet/hour)
The surface was scanned at 9 inches/minute with a locally oscillating laser beam of 1 W per hour using a shielding gas consisting of a flow of argon at a rate of 2 cubic feet per hour and a flow of hydrogen at 0.56 cubic feet per hour. The shape of the laser beam locally vibrates in the lateral direction, so it has a length of 0.25 (0.1
It was a rectangle measuring 0.5 inch (inch) by 1.27 inch (0.5 inch). The vibration rate was 690 hertz. Under these conditions, the steel plate surface was melted and intimately alloyed with carbon and chromium powder. Immediately after laser treatment, the steel plates were post-heated to 9000F. Preheating and postheating were performed in a furnace, and these treatments prevented cracking of the melting zone. Figure 19 shows the concentration of minor alloying components relative to chromium in the final product.

This curve has been fitted to the original data points (not shown) according to conventional statistical procedures. This curve shows a substantial increase in the concentration of chromium within the 50 mil deep melt zone. The concentration of chromium is 0.127
It was 21% by weight to a depth of arc (50 mils). 20th
The figure shows the change in hardness in the final product after laser treatment with localized vibrations.

In the melt zone, the hardness was Rockwell C53-57, whereas the hardness value of the steel plate without laser treatment was Rockwell C20. The hardness of the band castle subjected to thermal action was Rockwell C30. Second
Figure 1 shows that the laser-treated steel plate was subjected to local vibration laser treatment and then heated to 648.9℃ (12000℃) for an additional 2 hours.
F) shows the change in hardness of the final product that was subjected to furnace heat treatment and air cooled at the end of the heat treatment. In the melting zone, the hardness is 5 to
It was 5-58. The hardness of the band that was subjected to heat treatment was 25 at Lockhe's level. The curve in Figure 21 shows the resistance of the melt zone to one high temperature temper. The above-mentioned surface improvement method,
In the equipment and the resulting product, the processing time is very short.

In addition, the space, equipment, and cost burdens are light. There is little interference with the properties of the underlying substrate. Alloys and other mixtures are formed by introducing small amounts of alloying or blending components into the substrate. The resulting surface layer casing can be single phase or multiphase as described above in connection with Figures 6A-6D. The casing may be spatially continuous within the contour of its area or discontinuous within it. In most cases, the casing has a decreasing concentration gradient of minor components toward the underlying substrate, but at a certain depth within the gradient it has a spatially uniform composition. The invention applies to all types of cast iron,
and applicable to ferrous metals and alloys, including all types of steel.

The element or elements to be alloyed onto the surface of the metal article can be applied as a powder, or as a mixture of powders, or as an alloy powder, or as any suitable combination of the above. The present invention incorporates non-metallic materials into a substrate surface layer by mixing only minor components, such as those available from the well-known gas phase or from other minor sources, or without mixing any minor components. It can be applied in particular to mixing metal and non-metal materials and to physically modifying substrate surface layers.

As used herein, the term "gas phase" also includes sols and molecular beams under vacuum, as well as pure gases under atmospheric pressure, reduced pressure, and elevated pressure. Minor components introduced into the mixed surface layer can be reacted with the matrix phase during melting and mixing and/or reacted with the underlying substrate after melting and vaporized or eluted from the surface layer after the melting step, or Other post-melting post-treatments known per se can be carried out to further improve the properties of the casing product.

As can be seen, the present invention utilizes a single laser heat source on the workpiece.
It is not limited to achieving alloying of the surface layer or chemical reaction by the double-passing method.

Further alloying of the substrate after the first pass or addition of reactants and further heat application in the manner described may further modify the surface layer as described above. It will be apparent to those skilled in the art that various other uses and modifications of the specific embodiments described herein may be made without departing from the inventive concept once the advantages of the invention have been provided.

Accordingly, the present invention is to be construed as encompassing each and every novel feature and novel combination of features present in or belonging to the apparatus and method described above.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a sheet-shaped substrate part at an early stage of surface modification. FIG. 2 is a cross-sectional view of the above-mentioned parts of the same machine after the improvement has been completed. FIG. 3 is a schematic diagram of a preferred equipment arrangement for carrying out the method of the invention. Figures 4 and 5 are sketches of parts undergoing surface modification. Figure 6 and Figure 6A-6
Figure D is a micrograph of a cross section of a substrate whose surface has been improved. 7-9, 11, 12, 15 and 19 are concentration versus case depth curves for minor constituents introduced into the surface layer of a workpiece modified by the method according to the invention.
Figures 10, 13, 14, 16-18, 20-
FIG. 21 is a hardness vs. case depth curve for surface properties of a workpiece improved by the method according to the invention. rJC. J-rJG. Z ′′Yu. ] -To JG. 4 To J6.3 Sea bream sea bream ′ , , scallop chick trout connection green ball reduced sardine scale yield rYG. ' rJG・YO [JG. 3 JC. J〇・ ＾Y6. J2. 20,000 G. J3-LYC. 14 ZG. J Yu ZC. Z'・Y6. J〇・【YG. Z-LY^. Z-required 6.2Y

Claims (1)

[Claims] 1. A coating layer of one or more alloying components is applied to the surface of steel or cast iron, and then the coating layer surface is coated with a predetermined depth of the coating layer along a linear processing path. A process for surface alloying steel or cast iron comprising traversing the underlying steel or cast iron along said linear machining path with the output beam of a laser to melt, mix and resolidify the molten coating layer and the underlying layer. The laser beam is deflected to scan the coating surface in succession and traverse the coating layer along a number of linear machining paths located in parallel relationship. while the laser beam is the output beam of a continuous wave laser and has a 7.75
~1550KW/cm2 (50~10000KW/inch2) and a power density of 12.7~127cm/min (5
50 inches per minute).