JPH11124683A - Method for forming nonoxidized coating film by electroless composite plating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely eliminate hydrogen embrittlement and to prevent oxide from being formed as foreign matter on the surface layer by subjecting the object to be treated to vacuum firing treatment so that hydrogen occluded into composite plating film is degassed and a high polymer material dispersed into the coating is thermally deposited without forming oxide. SOLUTION: Vacuum firing is executed preferably in such a manner that it is divided into a degassing treating stage for degassing hydrogen executed at a relatively low temp. and a nonoxidizing treating stage executed at a temp. in which at least a high polymer material is melted or above. Thus, respective treating temps. can be set in accordance with the occluding state of hydrogen in composite plating coating and the characteristics of the high polymer material composing this coating film, so that more secure degassing of hydrogen and the prevention of the formation of oxide can be attained. Moreover, as for the matter that which is first executed between these two treating stages, it is not limited to either and is suitably selected in accordance with the occluding state of hydrogen, the characteristics of the high polymer material, the materials of the plating and the object to be treated or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to precision dies, cutting tools, etc., which are typified by composite eutectoid plating, with emphasis on corrosion resistance and releasability, and motor shafts, gears, casings, etc. usable without lubrication. In particular, the present invention relates to a method for forming a composite plating film, which is particularly frequently used as a coating film, that is, a coating film in which a metal and a polymer material are mixed, particularly, preventing hydrogen from being absorbed in the composite plating film and oxidizing the surface layer of the coating. The present invention relates to a method for post-treating a composite plating film so as to prevent an object from being formed.

[0002]

2. Description of the Related Art Hydrogen embrittlement of composite plating films,
The brittleness due to the occlusion of hydrogen in the coating,
The higher the strength of the polymer material constituting the coating, the more likely it is to occur,
It is known that the generation occurs even when the amount of hydrogen in the film is very small, such as 0.1 ppm or less. Since this hydrogen is in an atomic state, not only when performing a treatment for generating hydrogen gas, but also when no generation of hydrogen gas is recognized, pickling, acid immersion, cathodic electrolytic cleaning, electricity Plating, dissolution and peeling by plating acid, etc. (contamination of washing water depending on the material of the object to be treated) penetrates into the film, and it is extremely difficult to avoid hydrogen intrusion during pre-treatment and plating. Was.

On the other hand, the composite plating film is heated in an air furnace to remove the occluded hydrogen, relieve internal stress, remove lattice defects at the interface between the workpiece and the film, and react. A method has also been proposed in which formation of a layer, promotion of crystallization, and the like are also obtained. However, in this method, when the heating temperature exceeds 300 ° C., the surface layer of the coating generally undergoes deterioration and discoloration, and at the same time, the polymer material in the composite plating film melts to accelerate the deterioration and discoloration of the surface layer and oxidize. It was easy to form an oxide film. This not only impairs the properties of the polymer material itself applied to the coating and makes it impossible to achieve its intended purpose, but also causes oxides to be present as foreign matter in the surface layer, resulting in appearance, lubricity, abrasion resistance, It had the disadvantage that the tackiness and water repellency were impaired.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to completely eliminate hydrogen embrittlement by completely absorbing hydrogen absorbed by a coating film and to reliably prevent oxides from being formed as foreign matter on a surface layer. An object of the present invention is to provide a method for forming an electroless composite plating film that can be performed.

Another object of the present invention is to avoid deterioration and discoloration of the surface layer of the film and formation of an oxide film, thereby alleviating internal stress, removing lattice defects at the interface between the workpiece and the film, and forming a reaction layer. A method for forming an electroless composite plating film capable of promoting formation, crystallization, etc., and also ensuring the appearance, lubricity, abrasion resistance, non-adhesion, and water repellency of the film and increasing the strength of the film. Is to provide.

[0006]

According to the present invention, there is provided a method for forming an oxidation-free film by post-processing a composite plating film electrolessly plated on an object to be processed, the method comprising: Degassing the hydrogen and vacuum-treating the object plated with the composite plating film in a vacuum heat treatment furnace so that the polymer material dispersed in the film is thermally welded without generating an oxide. This is accomplished by:

[0007] In a vacuum heat treatment furnace, the boiling point of hydrogen is reduced by the action of reduced pressure, so that the evaporation ability of hydrogen absorbed in the composite plating film is greatly increased as compared with the heat treatment under atmospheric pressure, and the temperature is relatively low. Hydrogen can be surely degassed by the heat treatment in step (1). Also, the composite plating film containing a polymer material, which decomposes and degrades at high temperatures, is also a heat treatment at a relatively low temperature, so that decomposition and degeneration, etc. are reliably prevented from occurring, and Since the treatment is performed in a vacuum atmosphere, formation of an oxide can be reliably prevented.

[0008] The method according to the present invention further comprises a degassing step of performing the vacuum heat treatment in the vacuum heat treatment furnace at a relatively low temperature for degassing hydrogen; The treatment may be divided into a non-oxidation treatment step in which vacuum heat treatment is performed at a temperature higher than the temperature at which the material is melted. Separating the heat treatment into two stages of degassing and non-oxidizing treatments at different temperatures makes it possible to set the respective treatment temperatures according to the state of hydrogen absorption in the composite plating film and the characteristics of the polymer material constituting the composite plating film. This makes it possible to more reliably prevent degassing of hydrogen and formation of oxides. The method according to the present invention can also use an electroless nickel plating solution in which PTFE is dispersed in the electroless plating solution,
It is possible to form a metal surface coating excellent in appearance, lubricity, abrasion resistance, non-adhesion, and water repellency.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process chart showing a method for forming an oxidation-free film of electroless composite plating according to an embodiment of the present invention. The object A (see FIG. 2) is subjected to necessary pretreatments such as degreasing, washing, and activation in a pretreatment step 1, and
After the base plating film B (see FIG. 2) is attached in the electroless base plating process 2, a composite plating film C (see FIG. 2) is formed in the electroless composite plating process 3. However, the electroless base plating step 2 is not always a necessary step, and this step can be omitted depending on an object to be plated.

The steps from the pretreatment step 1 to the electroless composite plating step 3 are performed by conventional means. As is well known, these steps vary depending on the type of the object to be processed and the electroless plating solution, etc., but are roughly classified into those in which the material of the object to be processed is stainless steel, iron, steel, copper or a copper alloy, aluminum or aluminum. Alloys. In the case of the former, the pretreatment step 1 includes an alkali preliminary cleaning.
→ alkaline electrolytic cleaning → primary acid activity → electrolytic secondary acid activation, etc. In the latter case, alkali preliminary cleaning → alkali etching → acid activity → zincate is performed. In addition, when the object to be processed is a special material such as tungsten or titanium,
It is easily understood by those skilled in the art that this can be dealt with by changing the pretreatment liquid, and that other known pretreatment methods can be similarly applied. Similarly, the base plating film B is mainly used to enhance the affinity between the workpiece A and the composite plating film C, and the plating solution used in the electroless base plating step 2 is a well-known plating solution. It will be readily understood that the material is appropriately selected and applied depending on the materials of the object A and the composite plating film C.

In the electroless composite plating step 3, the object A, which is pre-treated and preferably under-plated, is coated with a composite plating film C having a predetermined thickness in an electroless metal plating solution in which a polymer material is dispersed. This is performed by immersion until is formed. Conditions such as a processing temperature, a processing time, and a composition of a processing solution in each of the above-described steps are performed according to a conventional method, and therefore, description thereof is omitted to avoid redundancy.

Workpiece A plated as described above
In the vacuum firing step 4, the vacuum heat treatment furnace 10 (FIG. 3)
And heat-treated in a vacuum atmosphere.
As a result, the hydrogen occluded in the composite plating film C attached to the processing object A evaporates at a lower temperature than in the normal state, and degasses the hydrogen. In addition, composite plating film C
The polymer material therein once melts at a lower temperature than in the normal state, and then crystallizes as the temperature is raised without forming an oxide. This is to ensure the relaxation of internal stress, removal of lattice defects at the interface between the workpiece and the film, formation of a reaction layer, and promotion of crystallization, etc., which were planned in the conventional heating method in the atmospheric furnace. At the same time, the deterioration and discoloration of the coating surface layer, which were disadvantages of the conventional heating method using the atmospheric furnace, the deterioration of the polymer material itself, and the appearance, lubricity and abrasion resistance of the coating due to oxide as a foreign matter,
It reliably prevents non-adhesion and adverse effects on water repellency.

Here, the vacuum firing step 4 includes a degassing step 4a in which a vacuum heat treatment is performed at a relatively low temperature for degassing hydrogen, and a vacuum step at a temperature at least at which the polymer material is melted. It is preferable that the heat treatment is performed separately from the non-oxidation treatment step 4b in which the heat treatment is performed. The heat treatment divided into the two treatment steps 4a and 4b can be performed at different temperatures depending on the occlusion state of hydrogen in the composite plating film and the characteristics of the polymer material constituting the composite plating film. Thus, more reliable prevention of degassing of hydrogen and formation of oxides can be achieved. On the other hand, which of the two processing steps 4a and 4b is performed first is not necessarily limited to one of them.
It can be appropriately selected according to the hydrogen storage state, the characteristics of the polymer material, the material of the plating and the object to be treated, and the like.

The vacuum heat treatment furnace 1 used in the present invention
Reference numeral 0 denotes a vacuum heat treatment furnace similar to that used for heat treatment of a metal workpiece, as shown in FIG. 3, a vacuum chamber 11 for accommodating an object to be processed in a sealed state, and a vacuum heat treatment furnace. A vacuum pump 12 for evacuating the inside of the tank 11
And a heater 13 for heating the inside of the vacuum chamber 11
And a water jacket 1 for cooling the inside of the vacuum chamber 11
And 4. An injection pipe 16 having a cooling gas injection valve 15 is connected to the vacuum chamber 11 so as to inject a cooling gas for cooling the inside of the vacuum chamber 11 again. The vacuum pump 12 is connected to the vacuum chamber 11 by an intake pipe 17.
And an exhaust pipe 18 for exhausting air exhausted from the vacuum chamber 11 by the vacuum pump 12 to the outside. In the figure, valves indicated by reference numerals 19 and 20 are a main valve for interrupting the connection between the vacuum chamber 11 and the vacuum pump 12, and a valve for interrupting the connection between the vacuum chamber 11 and the outside air, respectively. It is a leak valve.

The vacuum heat treatment furnace 10 puts the plated workpiece in a vacuum chamber 11 and hermetically closes it. The main valve 19 is opened and the vacuum pump 12 is operated to discharge the air inside the vacuum chamber 11. Vacuum is applied. Next, the heater 13 is operated to raise the temperature in the vacuum chamber 11 to degas the hydrogen and other gas components occluded in the composite plating film C and to melt the polymer material dispersed in the coating film. I do. At this time, the vacuum pump 12 is operated so as to always maintain a constant vacuum state, whereby the hydrogen and other gas components released from the composite plating film C are supplied to the suction pipe 16, the main valve 19 and the vacuum pump 12. Is exhausted from the exhaust pipe 15 via the When the degassing of hydrogen and the melting of the polymer material are performed, the main valve 19 is closed, the vacuum pump 12 is stopped, the cooling water flows into the water jacket 14, and the cooling gas injection valve 15 is opened to inject the cooling gas. The object to be processed is cooled to room temperature by injecting it from 16 into the vacuum chamber 11. At this time, the molten polymer material is crystallized without forming an oxide due to being in a vacuum atmosphere.

With respect to the degree of vacuum, heating temperature and processing time of the vacuum chamber 11 in the vacuum firing step 4, the higher the degree of vacuum, the lower the heating temperature or the shorter the processing time. On the other hand, it is necessary to heat the polymer material to a temperature higher than the melting temperature of the polymer material (lower than the temperature in the normal state), while it is necessary to completely degas hydrogen. Such a temperature can be sufficiently achieved at a relatively low temperature by lowering the boiling point under a vacuum state. Therefore, as described above, the vacuum firing step includes a degassing step in which vacuum heat treatment is performed at a relatively low temperature for degassing hydrogen, and a vacuum heat treatment step at least at a temperature at which the polymer material is melted. And a non-oxidation treatment step. Temperature management in these two processing stages is performed by appropriately controlling heating by the heater 13 and supply of cooling water to the water jacket 14 and / or injection of cooling gas into the vacuum chamber 11.

[0017]

EXPERIMENTAL EXAMPLE 1 A 200 × 200 × 2 mm stainless steel plate (SUS304) was used as the processing object A. After performing the conventional pretreatment (alkaline pre-cleaning, alkaline electrolytic cleaning, primary acid activity and electrolytic secondary acid activity), immersion in an electroless plating solution containing nickel sulfate and sodium hypophosphite as main components -A base plating film B of a phosphorus alloy was deposited. Next, the object A, which has been subjected to the base plating, is immersed in an electroless composite plating solution “Enlube Process (trade name)” manufactured by EBARA Uzilite Co., Ltd. to apply a composite plating film C on both surfaces ( Sample 1). Here, the electroless composite plating solution “Enlube Process” is obtained by adding PTFE as a polymer material and a dispersant to an electroless plating solution containing nickel sulfate and sodium hypophosphite as main components. The composite plating film C formed on the workpiece A was a film in which PTFE having a particle diameter of 1 μm or less was codeposited in a layer of a nickel-phosphorus alloy. The thickness of the composite plating film C on each surface of the workpiece A was 12 μm on average.

The object to be treated, that is, the sample 1, to which the composite plating film is attached, is placed in a vacuum chamber 11 of a vacuum heat treatment furnace 10.
Then, the container is sealed and the vacuum pump 12 is operated to operate the vacuum tank 1.
1 is evacuated, and the heater 13 is operated to activate the vacuum chamber 1
1 is maintained in the range of 350 to 370 ° C.
After heating for 5 minutes, cooling water was supplied to the water jacket 14 and a cooling gas was injected into the vacuum tank 11 to return the object to room temperature to prepare a sample 1a of the present invention. The pressure in the vacuum chamber 11 from the start of heating to the start of cooling was kept at 2 Pa or less.

On the other hand, similarly to the sample 1a, the sample 1 is placed in a vacuum chamber 11 of a vacuum heat treatment furnace 10 and hermetically closed.
Is brought into a vacuum state, and the heater 13 is operated to operate the 185-2.
Heat treatment was performed at a temperature of 00 ° C. for about 20 minutes. Next, the inside of the vacuum chamber 11 is further heated to a temperature of 350 to 370 ° C. for about 3 hours.
After the heat treatment for 0 minutes, the object to be processed was returned to room temperature to prepare another sample 1b of the present invention. The pressure in the vacuum chamber 11 from the start of heating to the start of cooling was similarly kept at 2 Pa or less.

For comparison, a sample 1x was prepared by subjecting the object to be treated (sample 1) to which the above-mentioned composite plating film was adhered to a known heat treatment in a conventional atmospheric furnace. The heating temperature in the air furnace was kept within 280 ± 5 ° C. to avoid the deterioration and discoloration of the surface layer of the coating and the melting of the polymer material in the composite plating coating.

Each of ten samples 1, 1a, 1b and 1x
About the measured hydrogen absorption amount in the composite plating film C from a change in the hydrogen amount in comparison with the substrate (the object itself) using a LECO RH-404 type hydrogen analyzer,
On average, sample 1 (untreated) 19.1 ppm sample 1a (invention) 1.4 ppm sample 1b (invention) 0.9 ppm sample 1x (comparative example) 13.4 ppm.

The surface oxide amount of each of the ten samples 1, 1a, 1b and 1x was measured by EPMA observation (20 kV / 15 mA / beam diameter 200 μm). The average value of the X-ray intensity PKI value was obtained. Sample 1 (untreated) 4.3 CPS Sample 1a (invention) 5.2 CPS Sample 1b (invention) 5.2 CPS Sample 1x (comparative example) 23.0 CPS.

From these measurements, it was found that Samples 1a and 1b provided with the composite plating film heat-treated by the method of the present invention.
In both the one-stage heat treatment and the two-stage heat treatment, the hydrogen storage amount is about 1/10 or more and the surface oxide amount is about 1/10 or more as compared with the conventional sample 1x heat-treated in an atmospheric furnace. It was found to be reduced by more than a quarter. Sample 1
The surface of x was discolored to dark brown, and it was visually confirmed that an oxide film was present, whereas samples 1a and 1b did not have an oxide film. Note that the measured value of the surface oxide amount of Sample 1 is smaller than that of Samples 1a and 1b of the present invention. This is because the heat treatment of Sample 1 does not cause oxidation of the coating due to the heat treatment. Will be easily understood.

[0024]

EXPERIMENTAL EXAMPLE 2 A 200 × 200 × 2 mm aluminum plate (Al 7075) was used as the processing object A. The object to be treated A is subjected to a pre-treatment and a base plating treatment in the same manner as in the above-mentioned experimental example, and then to a composite plating treatment, whereby a nickel-phosphorus alloy layer having a particle diameter of 1 μm or less as a polymer material is formed. A composite plating film on which PTFE was eutectoid was adhered (Sample 2).

Sample 2 was subjected to one-stage and two-stage vacuum firing treatments in a vacuum heat treatment furnace, respectively, to prepare samples 2a and 2b in the same manner as when preparing sample 1a and when preparing sample 1b, respectively. Sample 1x for comparison
In the same manner as when the sample 2 was prepared, the sample 2 was subjected to a well-known heat treatment (processing temperature: 280 ± 5 ° C.) in a conventional atmospheric furnace to obtain a sample 2
x was created.

These samples 2, 2a, 2b and 2x,
The hydrogen absorption amount and the surface oxide amount of the composite plating film C were measured for each of the ten sheets in the same manner as described in the experimental example, and, on average, << Hydrogen storage amount >> Sample 1 (untreated) 19 .1 ppm sample 1a (invention) 1.4 ppm sample 1b (invention) 1.1 ppm sample 1x (comparative example) 12.4 ppm << Amount of surface oxide >> sample 1 (untreated) 5.3 CPS sample 1a (Invention) 6.7 CPS sample 1b (Invention) 6.3 CPS sample 1x (Comparative example) 12.4 CPS (average value by X-ray intensity PKI value).

From these measurements, as in the experimental example,
Sample 1 by one-stage and two-stage vacuum heat treatment of the present invention
It was found that “a” and “1b” were reduced by about one-tenth or more in hydrogen storage amount and about one-half or more in surface oxide amount, as compared with Sample 1x heat-treated in an atmospheric furnace. Similarly,
While it was confirmed by visual observation that an oxide film was present on the surface of sample 2x (discolored to dark brown), samples 2a and 2b
There was no oxide film. Note that the measured value of the surface oxide amount of the sample 2 was because the oxidation of the film due to the absence of the heat treatment was avoided as described in the above example.

[0028]

According to the present invention, the object to which the composite plating film is adhered is subjected to vacuum baking treatment in the vacuum heat treatment furnace 10 so that the hydrogen absorbed in the composite plating film can be reliably degassed. Since the polymer material in the composite plating film can be once melted and welded without forming an oxide and then formed into a eutectoid film, a conventional heating method in an atmospheric furnace can be used. As in the above, it is possible to reliably alleviate internal stress, remove lattice defects at the interface between the object to be treated and the film, form a reaction layer, promote crystallization, and so on. The deterioration of the molecular material itself can be prevented, and the appearance, lubricity, abrasion resistance, non-adhesiveness, and water repellency of the coating film due to the oxide as a foreign substance can be reliably prevented from being impaired.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for forming an electroless composite plating film according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view schematically showing an object to be processed having a composite plating film formed by the method of FIG.

FIG. 3 is a schematic view showing an example of a vacuum heat treatment furnace used in the method of FIG.

[Explanation of symbols]

 Reference Signs List 1 Pretreatment step 2 Electroless base plating step 3 Electroless composite plating step 4 Vacuum baking step 4a Degassing step 4b Nonoxidizing step 10 Vacuum heat treatment furnace 11 Vacuum tank 12 Vacuum pump 13 Heater 14 Water jacket 15 Cooling gas injection Valve 16 Injection pipe 17 Intake pipe 18 Exhaust pipe 19 Main valve 20 Leakage valve A Workpiece B Base plating C Composite plating

Claims (3)

[Claims] 1. A method for forming an oxidation-free film by post-treating a composite plating film obtained by electroless plating an object to be processed, wherein the hydrogen absorbed in the composite plating film is degassed. A process in which the object to be plated with the composite plating film is vacuum-baked in a vacuum heat treatment furnace so that the polymer material dispersed in the film is thermally welded without generating an oxide. Method. 2. The vacuum baking treatment in the vacuum heat treatment furnace includes a degassing step of performing a vacuum heat treatment at a relatively low temperature for degassing hydrogen, and a temperature at least equal to or higher than a temperature at which the polymer material is melted. 2. The method according to claim 1, further comprising a non-oxidizing treatment step of performing a vacuum heat treatment in the step. 3. The method according to claim 1, wherein the electroless composite plating solution is an electroless nickel plating solution in which PTFE is dispersed.