Abstract A new process for electroplating diamond is proposed. The surface condition of the substrate is greatly improved by using mechanical grinding to descale the scale, adding alkali additives, anodizing and electrochemical degreasing methods. The process enhances the pre-plating treatment, solves the problem of poor adhesion of the plating layer, and improves the coating quality and service life of the plated parts.
Key words electroplating pre-treatment diamond DOI:
1 New process before plating
Diamond is the most abrasive and sharp abrasive grain currently found. The diamond abrasive is “plated†on the metal substrate by electroplating, which replaces the traditional die-casting method, which not only has low investment, low cost, but also avoids oxidation of the diamond under high temperature, and ensures the hardness and sharpness of the diamond.
In the entire electroplated diamond process, more than 90% of the plating layer is poorly bonded due to poor pre-plating treatment. Therefore, in order to improve the quality of plating, the most important thing is to do pre-plating treatment.
Pre-plating treatments include: degreasing, rust prevention, etching, pickling, activation cleaning, and the addition of auxiliary electrodes and mounting.
In order to improve the quality of the coating, after analyzing and comparing the electroplating industry at home and abroad, combined with the actual situation, the new process flow before plating is established as follows: deburring→cleaning→coating adhesive→scrubbing→chemical degreasing→hot and cold water washing → Pickling → cold water rinsing → electrochemical degreasing → rinsing → anodizing → rinsing into the tank.
1. Deburring sandpaper and handcuffs remove the burrs on the workpiece to prevent the surface of the workpiece from exhibiting a poor dielectric state.
2. Wash the workpiece with a rub of alcohol to remove the oil on the surface of the workpiece.
3. Apply the insulating glue to the workpiece after scrubbing, and apply a layer of quick adhesive on the non-plated part to insulate the non-plated part.
4. Scrub In order to prevent the plating part from being coated with insulating glue, polish the part again with hand rub or sandpaper, then rinse.
5. The chemical degreasing and degreasing agent formulation is shown in Table 1. .jpg)
Sodium hydroxide has a strong saponification effect and reacts with animal and vegetable oils to form soluble fly ash and glycerin.
Sodium lauryl sulfate is a surface active agent that reduces the surface tension between liquid and work with the synergy of its dodecyl hydrophobic group and sulfated hydrophilic group. It acts as an lye additive to speed up the degreasing.
Sodium carbonate and sodium silicate are two buffers that act to buffer the acid, leaving the pH of the melt essentially unchanged.
The workpiece was placed in the above solution and washed at 40 ° C to 60 ° C for about 30 minutes.
6. Heat, cold water rinse first with hot water, rinse with cold book to avoid the oil removal into the acid solution.
7. The pickling acid pickling formula is shown in Table 2, the purpose of which is to remove the scale on the surface of the substrate. .jpg)
8. After washing with cold water, pick up the workpiece, rinse it with cold water, and then attach it to the electrochemical deoiling tank.
9. Electro-chemical degreasing electrochemical degreaser formula is shown in Table 3. .jpg)
Hang the work in this solution, connect to the same source, first level for 1 minute, then anodize for 3 minutes. The current density used was 10 A/dm2 and the electrodes were stainless steel plates. The electrochemical degreasing reaction is as follows:
Yang grade degreasing: 4OH--2e=O2↑+H2O
Cathode degreasing: 2H++2e=H2↑
The combined degreasing method of the yin and the anodic pole has the advantages of quick degreasing speed and no hydrogen embrittlement.
10. Flushing The workpiece after electrochemical degreasing is washed and washed with a book, and ready for processing.
11. The formulation of the anodized anode treatment solution is shown in Table 4. The substrate is mounted and the plating site is inserted into the solution. A lead plate for a negative electrode and a base for a positive electrode. The current density is 25 A/dm2 and the energization time is 3 minutes. The positive treatment avoids the phenomenon of hydrogen embrittlement, and is especially suitable for the last process before entering the tank. .jpg)
12. Rinse into the tank After the anode-treated substrate is quickly rinsed, it is placed in a plating bath to prepare for electroplating.
At this point, the entire pre-plating treatment of diamond plating is completed.
2 Experimental results
In the experiment, the test pieces were divided into five groups, and pre-plating treatment was carried out under different pre-plating treatment processes, and then electroplating was carried out under the same plating conditions. The specific processing conditions of each group of test pieces are shown in Table 5. .jpg)
The sample was made of iron sheets of 15 × 15 × 2 mm 2 . During the experiment, the temperature was 40 ° C ± 1 ° C, the current density was 40 MA / dm 2 , the anode was a pure 2 nickel plate, and the cathode was a test piece.
The electroplated test piece was tested for both bonding strength and brittleness. The coating adhesion test is a qualitative experimental test method, namely the sickle test method. The so-called boring test method refers to the use of a boring tool to form a 45o 锉 coating edge from the substrate to the plating direction. If the coating is not taken up or peeled off, it is acceptable.
When the bonding force is good, the brittleness test of the plating layer is performed. The brittleness test uses a bending method. The bending method is repeated by bending the test piece on the vise, and the change of the bending part is observed with a magnifying glass until the first crack occurs.
It can be seen from the measurement results in Table 5 that with the new process, the surface of the test piece has good surface smoothness, the oil stain and the scale are removed, and the test piece exhibits a good plated state. The bonding strength between the plated metal and the base metal is good, and the uniformity and integrity of the plating layer are good.
3 Conclusion
1. Using mechanical deburring and honing the part to be plated to prevent the surface of the workpiece from exhibiting a poor dielectric state;
2. Sodium dodecyl sulfate is used as an alkali additive to enhance the activity of the surface of the substrate, and the oil removal speed is fast and the quality is good;
3. Use low temperature to remove oil, so that the substrate is not affected by thermal stress;
4. After chemical degreasing and pickling, electrochemical degreasing and anodizing are used to greatly change the state of the surface of the substrate, improve the dispersing ability and covering ability of the plating solution, and improve the uniformity and integrity of the coating. , enhanced adhesion of the coating.
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