Polycrystalline diamond suspension for metallographic sample preparation and preparation process thereof

Abstract

The invention relates to the technical field of polishing, in particular to a polycrystalline diamond suspension liquid for metallographic sample preparation and a preparation process thereof, and the polycrystalline diamond suspension liquid comprises the following components: hydroxyl modified polycrystalline diamond micro powder, a suspending agent, a composite surfactant, a thickening agent, an antioxidant, a chelating agent and deionized water; according to the polycrystalline diamond suspension liquid for metallographic sample preparation, through cooperation of component optimization and process improvement, the polishing efficiency and stability of the suspension liquid are remarkably improved. Through NaOH pretreatment, silane coupling agent grafting and roasting processes, the content of hydroxyl groups on the surface of the polycrystalline diamond micro-powder is larger than or equal to 1.2 mmol / g, a hydrophilic interface is formed, the Van der Waals force among particles is remarkably reduced, agglomeration can be effectively inhibited, meanwhile, the dispersity of suspension liquid is greatly improved by combining the synergistic effect of the composite surfactant, and the service life of the suspension liquid is prolonged. And polishing scratches are effectively reduced, and the polishing quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polishing, and particularly to a polycrystalline diamond suspension for metallographic sample preparation and a preparation process thereof. Background Art

[0002] In the process of metallographic sample preparation, polishing technology is one of the core links to obtain high-quality microstructures. Due to problems such as low efficiency and large surface damage in traditional mechanical grinding, chemical etching or electrolytic polishing processes, the precision polishing technology based on diamond suspension has gradually become the mainstream polishing choice due to its high hardness, low friction coefficient and excellent self-sharpening property.

[0003] Polycrystalline diamond micropowder is one of the important components in the suspension, which directly affects the polishing quality. However, the existing commercially available metallographic polishing fluids generally have the following technical defects: First, the suspension stability is poor. Traditional diamond suspensions rely on physical stirring or simple surfactant dispersion, resulting in easy agglomeration and sedimentation of polycrystalline diamond micropowder. Specifically, uneven particle size distribution of micropowder (such as too high proportion of particles >5μm) causes polishing scratches, and the suspension system is significantly affected by temperature and shear force, resulting in obvious stratification after standing; Second, the polishing performance is limited and the polishing quality is low; Third, the process compatibility is insufficient. Some polishing fluids contain organic solvents or corrosive components (such as nitrates), which are not environmentally friendly and limit their application scope. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a polycrystalline diamond suspension for metallographic sample preparation and a preparation process thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A polycrystalline diamond suspension for metallographic sample preparation is composed of the following components by weight percentage:

[0007] Hydroxyl-modified polycrystalline diamond micropowder: 3.5 - 6%;

[0008] Suspending agent: 1.5 - 2.5%;

[0009] Compound surfactant: 1 - 2%;

[0010] Thickening agent: 0.3 - 0.5%;

[0011] Antioxidant: 0.08 - 0.1%;

[0012] Chelating agent: 0.02 - 0.04%;

[0013] Deionized water: the balance.

[0014] As a further technical solution, the average particle size of the hydroxyl-modified polycrystalline diamond micropowder is 0.8 - 2.5 μm, and the surface hydroxyl content is ≥ 1.2 mmol / g.

[0015] As a further technical solution, the preparation method of the hydroxyl-modified polycrystalline diamond micropowder comprises the following steps:

[0016] (1) First, add the polycrystalline diamond micropowder to a sodium hydroxide solution, adjust the temperature to 55 - 60 °C, keep it warm and stir in a water bath for 1 - 1.5 hours, then filter and wash until neutral to obtain pretreated polycrystalline diamond micropowder;

[0017] Among them, the mass fraction of the sodium hydroxide solution is 10 - 12%;

[0018] (2) Add the obtained pretreated polycrystalline diamond micropowder to an ethanol solution of γ-glycidoxypropyltrimethoxysilane, adjust the temperature to 65 - 70 °C, perform ultrasonic dispersion treatment for 20 - 30 min, then perform suction filtration and dry at 60 °C for 4 hours;

[0019] (3) Place the dried polycrystalline diamond micropowder in a tube furnace, introduce air, perform calcination treatment at 250 - 280 °C for 2 - 2.5 h, and then cool to room temperature to obtain.

[0020] As a further technical solution, the mass fraction of γ-glycidoxypropyltrimethoxysilane in the ethanol solution of γ-glycidoxypropyltrimethoxysilane is 2 - 2.6 wt%;

[0021] The ultrasonic dispersion power is 200 W and the frequency is 35 kHz.

[0022] As a further technical solution, the composite surfactant is composed of an anionic surfactant and a non-ionic surfactant;

[0023] Among them, the mixing mass ratio of the anionic surfactant to the non-ionic surfactant is 5:1 - 1.2;

[0024] The anionic surfactant is composed of sodium dodecylbenzenesulfonate and sodium fatty alcohol polyoxyethylene ether sulfate;

[0025] The non-ionic surfactant is fatty alcohol polyoxyethylene ether.

[0026] As a further technical solution, the preparation method of the composite surfactant comprises:

[0027] (1) First, mix sodium dodecylbenzenesulfonate and sodium fatty alcohol polyoxyethylene ether sulfate in a mass ratio of 2:1 evenly, and then add it to deionized water and stir for 20 min to obtain a preliminary solution;

[0028] The mixing mass ratio of sodium dodecylbenzenesulfonate to deionized water is 1:3;

[0029] (2) Add fatty alcohol polyoxyethylene ether to the above preliminary solution, adjust the temperature to 75 °C, keep warm and stir for 30 min to obtain;

[0030] Among them, the stirring speed is 3500 r / min.

[0031] As a further technical solution, the suspending agent is sodium carboxymethyl cellulose;

[0032] The thickening agent is polyvinyl alcohol;

[0033] Among them, the molecular weight of polyvinyl alcohol is 60000 - 70000;

[0034] The antioxidant is L-ascorbyl palmitate;

[0035] The chelating agent is disodium ethylenediaminetetraacetate.

[0036] A preparation process of a polycrystalline diamond suspension, comprising the following steps:

[0037] (1) First, heat deionized water to 45 - 50 °C, keep it in a water bath for 10 min, and then sequentially add a suspending agent and a thickening agent to the deionized water, and stir until completely dissolved;

[0038] The stirring speed is 150 r / min;

[0039] (2) Then cool down to 28 - 32 °C, sequentially add a composite surfactant, a chelating agent and an antioxidant, and continue stirring for 20 - 30 min;

[0040] The stirring speed is 120 r / min;

[0041] (3) Finally, slowly add hydroxyl-modified polycrystalline diamond micropowder, first stir at a speed of 300 r / min for 15 min, then perform ultrasonic dispersion for 20 - 25 min, and finally stir at a speed of 500 r / min for 1 - 1.5 h, and finally obtain the finished product through encapsulation.

[0042] As a further technical solution, in step (3), the ultrasonic dispersion power is 350 - 400 W and the frequency is 50 kHz.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] The polycrystalline diamond suspension for preparing metallographic samples provided by the present invention significantly improves the polishing efficiency and stability of the suspension through the cooperation of composition optimization and process improvement.

[0045] Through the processes of NaOH pretreatment, silane coupling agent grafting and calcination, the present invention enables the surface hydroxyl content of polycrystalline diamond micropowder to be ≥1.2 mmol / g, forming a hydrophilic interface, significantly reducing the van der Waals force between particles, effectively inhibiting agglomeration. Meanwhile, combined with the synergistic effect of the composite surfactant, the dispersibility of the suspension is greatly improved, effectively reducing the generation of polishing scratches and improving the polishing quality.

[0046] After modification, the surface active sites of the polycrystalline diamond micropowder increase, the contact area with the metallographic sample material expands. Coupled with the high fluidity of the suspension, the polishing time of the metallographic sample is significantly shortened, and the efficiency is increased by more than 20% compared with the traditional process.

[0047] The present invention introduces an anionic surfactant to maintain particle dispersion through electrostatic repulsion, and a non-ionic surfactant provides a steric hindrance effect, which can greatly improve the dispersion stability of the suspension.

[0048] By compounding sodium carboxymethyl cellulose (suspending agent) with low molecular weight polyvinyl alcohol, a three-dimensional network structure is formed to stabilize the viscosity of the suspension, ensuring both the suspension of the micropowder and avoiding excessive adhesion.

[0049] The suspension of the present invention does not contain organic solvents or corrosive components, meeting the development theme of green environmental protection.

[0050] In summary, through the interface optimization of hydroxyl-modified micropowders, the synergistic stability of composite surfactants and the functional matching of all components, the present invention breaks through the technical bottlenecks of poor stability and low efficiency of traditional polishing fluids, realizing the high-efficiency, precision and greening of metallographic sample preparation.

[0051] Description of the Drawings

[0052] Figure 1 It is a statistical bar chart of the roughness of each group in the examples and comparative examples. Detailed Embodiments

[0053] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0054] Example 1

[0055] In this example, the polycrystalline diamond suspension for metallographic sample preparation is composed of the following components by weight percentage:

[0056] Hydroxyl-modified polycrystalline diamond micropowder: 3.5%;

[0057] Sodium carboxymethyl cellulose: 1.5%;

[0058] Compound surfactant: 1%;

[0059] Polyvinyl alcohol (molecular weight 60000): 0.3%;

[0060] L-ascorbyl palmitate: 0.08%;

[0061] Disodium ethylenediaminetetraacetate: 0.02%;

[0062] Deionized water: the balance

[0063] The average particle size of the hydroxy-modified polycrystalline diamond micropowder is 0.8 μm, and the surface hydroxy content is 1.2 mmol / g. Its preparation method is as follows:

[0064] (1) Add the polycrystalline diamond micropowder to a 10% sodium hydroxide solution by mass, keep it warm and stir in a water bath at 55 °C for 1 hour, and filter and wash until neutral;

[0065] (2) Add a 2% ethanol solution of γ-glycidoxypropyltrimethoxysilane, disperse it by ultrasonic wave at 65 °C for 20 minutes (power 200 W, frequency 35 kHz), and dry it at 60 °C for 4 hours after suction filtration;

[0066] (3) Bake it in air at 250 °C in a tubular furnace for 2 hours, and obtain it after cooling.

[0067] The compound surfactant is composed of sodium dodecylbenzenesulfonate and sodium lauryl polyoxyethylene ether sulfate with a mass ratio of 2:1, which are mixed and then mixed with fatty alcohol polyoxyethylene ether in a ratio of 5:1. The preparation method is as follows:

[0068] (1) Mix sodium dodecylbenzenesulfonate and deionized water in a ratio of 1:3 and stir for 20 minutes;

[0069] (2) Add sodium lauryl polyoxyethylene ether sulfate, keep it warm and stir at 75 °C for 30 minutes, and the rotation speed is 3500 r / min.

[0070] Suspension preparation process:

[0071] (1) Add sodium carboxymethyl cellulose and polyvinyl alcohol to deionized water at 45 °C and stir at 150 r / min until dissolved;

[0072] (2) Cool down to 28 °C, and successively add the compound surfactant, disodium ethylenediaminetetraacetate and L-ascorbyl palmitate, and stir at 120 r / min for 20 minutes;

[0073] (3) Slowly add the hydroxyl-modified polycrystalline diamond micropowder. First, stir at 300 r / min for 15 minutes, then ultrasonically disperse at a power of 400 W for 20 minutes with a frequency of 50 kHz. Finally, stir at 500 r / min for 1 hour and encapsulate to obtain the finished product.

[0074] Example 2

[0075] The difference between this example and Example 1 is as follows:

[0076] Hydroxyl-modified polycrystalline diamond micropowder: 5%; average particle size 1.2 μm, surface hydroxyl content 1.5 mmol / g;

[0077] Sodium carboxymethyl cellulose: 2%;

[0078] Compound surfactant: 1.5%; mass ratio of anionic surfactant to nonionic surfactant is 5:1.1; Polyvinyl alcohol: 0.4%; molecular weight 65000;

[0079] Disodium ethylenediaminetetraacetate: 0.03%;

[0080] In the preparation process:

[0081] Mass fraction of sodium hydroxide solution is 11%;

[0082] Mass fraction of γ-glycidoxypropyltrimethoxysilane ethanol solution is 2.3%;

[0083] Ultrasonic dispersion power is 350 W, frequency is 50 kHz.

[0084] Example 3

[0085] The difference between this example and Example 1 is as follows:

[0086] Hydroxyl-modified polycrystalline diamond micropowder: 6%; average particle size 2.5 μm, surface hydroxyl content 1.8 mmol / g;

[0087] Sodium carboxymethyl cellulose: 2.5%;

[0088] Compound surfactant: 2%; mass ratio of anionic surfactant to nonionic surfactant is 5:1.2;

[0089] Polyvinyl alcohol: 0.5%; molecular weight 70000;

[0090] Disodium ethylenediaminetetraacetate: 0.04%;

[0091] In the preparation process:

[0092] Mass fraction of sodium hydroxide solution is 12%;

[0093] Mass fraction of γ-glycidoxypropyltrimethoxysilane ethanol solution is 2.6%;

[0094] The ultrasonic dispersion power is 400 W and the frequency is 50 kHz.

[0095] Comparative Example 1

[0096] Unmodified polycrystalline diamond micropowder (average particle size 1.0 μm) was used, and other components were the same as those in Example 1.

[0097] Comparative Example 2

[0098] Only sodium dodecylbenzenesulfonate was used as the composite surfactant, and other components were the same as those in Example 1.

[0099] Comparative Example 3

[0100] The ultrasonic dispersion step was omitted, and only mechanical stirring was used, and other processes were the same as those in Example 1.

[0101] Test

[0102] Dispersion stability test: The samples of the examples and comparative examples (both 150 mL) were left standing at normal temperature and pressure for 10 days, and then the layering situation of each group was observed;

[0103] Table 1

[0104]

[0105]

[0106] As can be seen from Table 1, the suspension prepared by the present invention has excellent stability.

[0107] The polishing performance test was carried out using a standard metallographic specimen (45# steel). The suspensions of the examples and comparative examples were used for polishing respectively. The polishing time was 15 minutes, and a white light interferometer was used to measure the surface roughness Ra value of the specimens polished with the suspensions of the examples and comparative examples:

[0108] Table 2

[0109] Surface roughness Ra Example 1 0.082 Example 2 0.069 Example 3 0.071 Comparative Example 1 0.155 Comparative Example 2 0.101 Comparative Example 3 0.095

[0110] As can be seen from Table 2, the suspension of the present invention can improve the polishing effect.

[0111] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification.

Claims

1. A polycrystalline diamond suspension for metallographic sample preparation, characterized in that: The composition by weight percentage is: Hydroxyl modified polycrystalline diamond powder: 3.5-6%; Suspension agent: 1.5-2.5%; Complex surfactant: 1-2%; Thickener: 0.3-0.5%; Antioxidant: 0.08-0.1%; Chelating agent: 0.02-0.0.4%; Deionized water: balance.

2. The polycrystalline diamond suspension for metallographic sample preparation according to claim 1, characterized in that: The average particle size of the hydroxyl-modified polycrystalline diamond powder is 0.8-2.5 μm, and the surface hydroxyl content is ≥1.2 mmol / g.

3. A polycrystalline diamond suspension for metallographic sample preparation according to claim 2, characterized in that: The method for preparing the hydroxyl-modified polycrystalline diamond powder comprises the following steps: (1) First, add polycrystalline diamond powder to a sodium hydroxide solution, adjust the temperature to 55-60° C., keep warm in a water bath and stir for 1-1.5 hours, then filter and wash until neutral to obtain pretreated polycrystalline diamond powder; Among them, the mass fraction of sodium hydroxide solution is 10-12%; (2) adding the pretreated polycrystalline diamond powder obtained above to an ethanol solution of γ-glycidyloxypropyltrimethoxysilane, adjusting the temperature to 65-70° C., ultrasonically dispersing for 20-30 min, then filtering, and drying at 60° C. for 4 hours; (3) The dried polycrystalline diamond powder is placed in a tubular furnace and air is introduced, and calcined at 250-280° C. for 2-2.5 h, and then cooled to room temperature to obtain.

4. The polycrystalline diamond suspension for metallographic sample preparation according to claim 3, characterized in that: The mass fraction of γ-glycidyloxypropyltrimethoxysilane in the ethanol solution of γ-glycidyloxypropyltrimethoxysilane is 2-2.6wt%; The ultrasonic dispersion power was 200 W and the frequency was 35 kHz.

5. The polycrystalline diamond suspension for metallographic sample preparation according to claim 1, characterized in that: The composite surfactant is formed by mixing an anionic surfactant and a nonionic surfactant; Wherein, the mixing mass ratio of anionic surfactant to nonionic surfactant is 5:1-1.2; The anionic surfactant is a mixture of sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene ether sulfate; The nonionic surfactant is fatty alcohol polyoxyethylene ether.

6. The polycrystalline diamond suspension for metallographic sample preparation according to claim 5, characterized in that: The preparation method of the composite surfactant comprises: (1) First, sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene ether sulfate were mixed uniformly in a mass ratio of 2:1, and then added into deionized water and stirred for 20 minutes to obtain a preliminary solution; The mixing mass ratio of sodium dodecylbenzene sulfonate and deionized water is 1:3; (2) Add fatty alcohol polyoxyethylene ether to the preliminary solution, adjust the temperature to 75° C., and stir for 30 minutes to obtain; Among them, the stirring speed is 3500r / min.

7. The suspension according to claim 1, characterized in that The suspending agent is sodium carboxymethyl cellulose; The thickener is polyvinyl alcohol; Wherein, the molecular weight of polyvinyl alcohol is 60000-70000; The antioxidant is L-ascorbyl palmitate; The chelating agent is disodium EDTA.

8. The process for preparing a polycrystalline diamond suspension for metallographic sample preparation according to claim 1, characterized in that: The following steps are involved: (1) First, heat deionized water to 45-50°C and keep it in a water bath for 10 minutes. Then, add the suspending agent and thickener to the deionized water in sequence and stir until they are completely dissolved. The stirring speed is 150r / min; (2) cooling the mixture to 28-32°C, adding the composite surfactant, chelating agent and antioxidant in sequence, and continuing stirring for 20-30 minutes; The stirring speed is 120r / min; (3) Finally, slowly add the hydroxyl-modified polycrystalline diamond powder, stir at 300 r / min for 15 min, then disperse by ultrasonic for 20-25 min, and finally stir at 500 r / min for 1-1.5 h, and finally package to obtain the finished product.

9. The process for preparing a polycrystalline diamond suspension for metallographic sample preparation according to claim 8, characterized in that: In step (3), the ultrasonic dispersion power is 350-400 W and the frequency is 50 kHz.

Images