A chemical mechanical polishing liquid for 440C stainless steel and its preparation method

Abstract

The present invention discloses a chemical mechanical polishing liquid for 440C stainless steel and a preparation method thereof, belonging to the technical field of chemical mechanical polishing liquids. The polishing liquid comprises abrasive particles, a pH adjusting agent, an oxidant, a dispersant, and deionized water; the abrasive particles are a mixture of silicon oxide and neodymium oxide; the pH adjusting agent is at least one of oxalic acid, malic acid, and glycine; the oxidant is at least one of H2O2 and KMnO4; and the dispersant is at least one of polyethylene glycol, polyvinyl alcohol, and sorbitol. This polishing liquid utilizes the synergistic effect of neodymium oxide and silicon oxide to prevent excessive corrosion and achieve uniform polishing. This polishing liquid can significantly improve the polishing quality and efficiency of 440C stainless steel, achieving near-atomic-level surface polishing. Furthermore, each component is non-toxic, environmentally friendly, and the preparation method is simple, making it suitable for large-scale promotion and application.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical mechanical polishing liquids, and in particular to a chemical mechanical polishing liquid for 440C stainless steel and a preparation method thereof. Background Art

[0002] 440C stainless steel components, as the main body and core supporting the operation of high-end key equipment such as aerospace, rail transportation, etc., such as space high-speed bearings and precision valve pairs, often have the characteristics of high precision, difficult to repair and difficult to disassemble. The quality of their surface directly determines the performance, life and reliability of the equipment.

[0003] Chemical mechanical polishing (CMP) combines traditional chemical etching with mechanical removal to achieve material removal from workpiece surfaces. Currently, polishing fluids used for 440C stainless steel contain toxic and hazardous components, such as nitric acid and sulfuric acid. These components pose a risk to operators and harm the environment. Furthermore, polishing efficiency is low and the ability to achieve near-atomic-level surface finishes is limited. The best known polishing results are limited to a roughness of 0.68 nm. Therefore, there is an urgent need for a green and environmentally friendly CMP fluid that can achieve near-atomic-level surface finishes. Summary of the Invention

[0004] The present invention provides a chemical mechanical polishing liquid for 440C stainless steel and a preparation method thereof, in order to solve the above problems.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A chemical mechanical polishing solution for 440C stainless steel, comprising abrasive particles, a pH adjusting agent, an oxidizing agent, a dispersant, and deionized water;

[0007] The abrasive particles are a mixture of silicon oxide and neodymium oxide; the particle size of the silicon oxide is in the range of 10 to 100 nm, and the particle size of the neodymium oxide is in the range of 20 to 50 nm; the mass ratio of the silicon oxide to the neodymium oxide is (25 to 30):1;

[0008] The pH adjusting agent is at least one of oxalic acid, malic acid, and glycine;

[0009] The oxidant is at least one of H2O2 and KMnO4;

[0010] The dispersant is at least one of polyethylene glycol, polyvinyl alcohol and sorbitol.

[0011] Furthermore, in terms of mass percentage, the mass of the abrasive is 0.5% to 25% of the total mass of the polishing liquid, the mass of the oxidant is 0.5% to 5% of the total mass of the polishing liquid, the mass of the dispersant is 0.02% to 2% of the total mass of the polishing liquid, and the remainder is the deionized water and the pH adjusting agent.

[0012] Furthermore, the pH of the polishing liquid is 3-7.

[0013] A method for preparing a chemical mechanical polishing liquid for 440C stainless steel comprises the steps of: mixing abrasive particles, a pH adjusting agent, an oxidizing agent, a dispersant, and deionized water in the following mass proportions to prepare the polishing liquid, wherein the mass proportion of the abrasive particles in the polishing liquid is 0.5 to 25 wt%, the mass proportion of the oxidizing agent in the polishing liquid is 0.5 to 5 wt%, the mass proportion of the dispersing agent in the polishing liquid is 0.02 to 2 wt%, and the remainder is the deionized water and the pH adjusting agent.

[0014] Furthermore, the silicon oxide and the neodymium oxide are first mixed in proportion, and then the oxidant, the dispersant and the deionized water are added in sequence and stirred evenly, and then the pH adjusting agent is added to adjust the pH to 3-7 to obtain the polishing liquid.

[0015] Furthermore, the mass ratio of the silicon oxide to the neodymium oxide is (25-30):1.

[0016] The beneficial effects of the present invention are:

[0017] (1) The chemical mechanical polishing liquid for 440C stainless steel disclosed in the present invention utilizes the synergistic effect of neodymium oxide and silicon oxide. Neodymium oxide can promote the decomposition of H2O2 to produce hydroxyl radicals, thereby accelerating the oxidation of Fe and Cr elements in stainless steel. The surface of silicon oxide adsorbs Fe. 3+ , forming Fe-O-Si bonds, while Nd 3+ A Nd(OH)3 protective layer will be formed on the stainless steel surface to prevent excessive corrosion and achieve uniform polishing. This polishing liquid can significantly improve the polishing quality and polishing efficiency of 440C stainless steel and can achieve a polishing effect of a near-atomic level surface.

[0018] (2) The components used in this polishing liquid are non-toxic and will not cause harm to operators and the environment, which is in line with the concept of green environmental protection;

[0019] (3) The preparation method of this polishing liquid is simple, low-cost, and easy to apply in large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 1(a) is the surface morphology and roughness measured by white light interferometer, and 1(b) is the optical surface morphology;

[0022] Figure 2 2(a) is the surface morphology and roughness measured by white light interferometer, and 2(b) is the optical surface morphology;

[0023] Figure 3 3(a) is the surface morphology and roughness measured by white light interferometer, and 3(b) is the optical surface morphology;

[0024] Figure 4 4(a) is the surface morphology and roughness detected by white light interferometer, and 4(b) is the optical surface morphology;

[0025] Figure 5 5(a) is the surface morphology and roughness detected by white light interferometer, and 5(b) is the optical surface morphology;

[0026] Figure 6 6(a) is the surface morphology and roughness detected by white light interferometer, and 6(b) is the optical surface morphology;

[0027] Figure 7 7(a) is the surface morphology and roughness detected by white light interferometer, and 7(b) is the optical surface morphology;

[0028] Figure 8 8(a) is the surface morphology and roughness detected by white light interferometer, and 8(b) is the optical surface morphology;

[0029] Figure 9 9(a) is the surface morphology and roughness measured by white light interferometer, and 9(b) is the optical surface morphology;

[0030] Figure 1010(a) is the surface morphology and roughness measured by white light interferometer, and 10(b) is the optical surface morphology;

[0031] Figure 11 These are the polishing effect diagrams of comparative example 8 of the present invention, wherein 11(a) is the surface morphology and roughness detected by a white light interferometer, and 11(b) is the optical surface morphology. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] The principles of this application are:

[0034] (1) 440C stainless steel is the hardest stainless steel, and the hardness of cerium oxide is lower than that of neodymium oxide, resulting in low mechanical removal efficiency of cerium oxide in chemical mechanical polishing. The harder neodymium oxide particles used in this scheme can more effectively remove the raised parts of the stainless steel surface, resulting in a better polishing effect. At the same time, in an acidic environment, cerium oxide will undergo a dissolution reaction as shown in Formula 1, resulting in a decrease in the concentration of cerium oxide and a loss of its dynamic oxidation ability, making it impossible to effectively remove the passivation film. However, the neodymium oxide used in this scheme is not easily soluble in an acidic environment, and its surface charge characteristics enable it to be better dispersed in the polishing liquid, improving the efficiency and quality of polishing; (1)

[0035] (2) Under acidic conditions, silicon oxide abrasives will adsorb Ce 3+ , which leads to agglomeration of abrasive particles and uneven polishing. If cerium oxide is used, it will form complex oxides with elements such as iron and chromium on the surface of stainless steel, making it difficult to form a synergistic effect with silicon oxide to effectively polish the stainless steel surface. Neodymium oxide can form soluble salts with elements such as iron and chromium on the surface of stainless steel, which helps to better mechanically remove silicon oxide particles from the stainless steel surface. At the same time, the hardness difference between silicon oxide and neodymium oxide is large. Neodymium oxide abrasive particles will preferentially break up the dense oxide layer, while silicon oxide refines the surface through shearing. The two work together to achieve high-efficiency, low-roughness polishing.

[0036] Example 1:

[0037] A chemical mechanical polishing liquid for 440C stainless steel comprises silicon oxide, neodymium oxide, malic acid, 30% H2O2, polyethylene glycol, sorbitol, and deionized water. The silicon oxide comprises two particle sizes: 10 nm and 50 nm. The 10 nm silicon oxide abrasive particles account for 12-15 wt %, the 50 nm silicon oxide abrasive particles account for 2-5 wt %, the 20 nm neodymium oxide accounts for 0.5-2 wt %, and the 30% H2O2 accounts for 0.5-1.5 wt %. The polyethylene glycol accounts for 0.1-0.2 wt %, the sorbitol accounts for 0.2-0.3 wt %, and the balance is deionized water. The pH value is adjusted to 4.5 by malic acid. The above wt % represents mass percentage. The mass ratio of the 10 nm silicon oxide, 50 nm silicon oxide, and 20 nm neodymium oxide is 25:4:1. The ratio of polyethylene glycol to sorbitol is 1:2.

[0038] Polishing liquid preparation method: According to the above proportions, 10nm silica, 50nm silica and 20nm neodymium oxide abrasives are mixed, and then 30% H2O2, polyethylene glycol, sorbitol and deionized water are added in sequence, stirred evenly, and then malic acid is added to adjust the pH to 4.5 to prepare the polishing liquid.

[0039] Example 2:

[0040] A chemical mechanical polishing liquid for 440C stainless steel comprises silicon oxide, neodymium oxide, glycine, 30% H2O2, sorbitol, and deionized water. The chemical mechanical polishing liquid comprises 15-18 wt % of 20 nm silicon oxide abrasive particles, 0.5-0.8 wt % of 20 nm neodymium oxide, 1-3 wt % of 30% H2O2, 0.2-0.4 wt % of sorbitol, and the balance is deionized water. The pH value is adjusted to 3 using glycine. The above wt % represents mass percentage, and the mass ratio of 20 nm silicon oxide to 20 nm neodymium oxide is 30:1.

[0041] Example 3:

[0042] A chemical mechanical polishing liquid for 440C stainless steel comprises silicon oxide, neodymium oxide, malic acid, 30% H2O2, polyethylene glycol, and deionized water. The chemical mechanical polishing liquid comprises 20-25% by weight of 50nm silicon oxide abrasive particles, 0.8-1.5% by weight of 20nm neodymium oxide particles, 3-5% by weight of 30% H2O2 particles, 0.5-2% by weight of polyethylene glycol, and the balance is deionized water. The pH value is adjusted to 5 by malic acid. The above wt% represents mass percentage, and the mass ratio of 50nm silicon oxide to 20nm neodymium oxide particles is 25:1.

[0043] The polishing liquid preparation method is the same as that in Example 1.

[0044] Comparative Example 1:

[0045] A chemical mechanical polishing liquid for 440C stainless steel comprises silicon oxide, oxalic acid, 30% H2O2, polyethylene glycol, and deionized water. The silicon oxide abrasive particles with a particle size of 200 nm account for 20-25% by weight, the 30% H2O2 solution accounts for 3-5% by weight, the polyethylene glycol accounts for 0.5-0.8% by weight, and the balance is deionized water. The pH value of the polishing liquid is adjusted to 4 by using oxalic acid. The above wt% represents the percentage by mass.

[0046] The polishing liquid preparation method is the same as that in Example 1.

[0047] Comparative Example 2:

[0048] A chemical mechanical polishing solution for 440C stainless steel comprises silicon oxide, oxalic acid, glycine, 30% H2O2, polyethylene glycol, polyvinyl alcohol, and deionized water. The silicon oxide has two particle sizes: 100 nm and 200 nm. The 200 nm silicon oxide abrasive particles account for 10-15% by weight, the 100 nm silicon oxide abrasive particles account for 5-10% by weight, the 30% H2O2 content accounts for 0.5-2% by weight, the polyethylene glycol accounts for 1-2% by weight, and the polyvinyl alcohol accounts for 2-5% by weight. The remainder is deionized water. The pH value is adjusted to 5.0 using oxalic acid and glycine. The above wt% represents mass percentage. The mass ratio of 200 nm silicon oxide to 100 nm silicon oxide is 2:1, the mass ratio of oxalic acid to glycine is 1:5, and the mass ratio of polyethylene glycol to polyvinyl alcohol is 1:2.5.

[0049] The polishing liquid preparation method is the same as that in Example 1.

[0050] Comparative Example 3:

[0051] A chemical mechanical polishing liquid for 440C stainless steel comprises neodymium oxide, malic acid, 30% H2O2, polyethylene glycol, and deionized water. The 100nm-diameter neodymium oxide abrasive accounts for 10-15wt%, the 30% H2O2 accounts for 1-3wt%, the polyethylene glycol accounts for 2-5wt%, and the balance is deionized water. The pH value is adjusted to 5.5 by malic acid. The above wt% represents mass percentage.

[0052] The polishing liquid preparation method is the same as that in Example 1.

[0053] Comparative Example 4:

[0054] A chemical mechanical polishing liquid for 440C stainless steel, comprising neodymium oxide, oxalic acid, malic acid, glycine, 30% H2O2, KMnO4, polyethylene glycol, polyvinyl alcohol, sorbitol and deionized water, wherein the abrasive particles are 20nm and 50nm of neodymium oxide, wherein the 20nm neodymium oxide abrasive particles are 8-10wt% and the 50nm neodymium oxide abrasive particles are 8-10wt% and 8-10wt% of the 20nm neodymium oxide abrasive particles are 8-10wt% and 8-10wt% of the 5 ...20nm neodymium oxide abrasive particles The neodymium oxide abrasive is 3-5wt% of neodymium oxide, 30% of H2O2 is 3-5wt% of H2O2, 0.02-0.5wt% of polyethylene glycol, 0.02-0.5wt% of polyvinyl alcohol, 0.02-0.5wt% of sorbitol, and the balance is deionized water. The pH value is adjusted to 7 by oxalic acid, malic acid, and glycine. The above wt% represents mass percentage; the mass ratio of 20nm neodymium oxide to 50nm neodymium oxide is 3:1, the mass ratio of oxalic acid, malic acid, and glycine is 1:1:2, and the mass ratio of polyethylene glycol, polyvinyl alcohol, and sorbitol is 1:1:1.

[0055] The polishing liquid preparation method is the same as that in Example 1.

[0056] Comparative Example 5:

[0057] A chemical mechanical polishing liquid for 440C stainless steel comprises silicon oxide, neodymium oxide, malic acid, KMnO4, polyvinyl alcohol, and deionized water. The silicon oxide comprises two particle sizes, 200 nm and 500 nm. The silicon oxide abrasive particles with a particle size of 500 nm account for 5-10 wt%, and the silicon oxide abrasive particles with a particle size of 200 nm account for 1-3 wt%. The neodymium oxide with a particle size of 100 nm accounts for 0.5-1 wt%, the KMnO4 accounts for 0.2-0.5 wt%. The polyvinyl alcohol accounts for 1-2 wt%, and the balance is deionized water. The pH value of the polishing liquid is adjusted to 5 by malic acid. The above wt% represents mass percentage. The mass ratio of the 500 nm silicon oxide, the 200 nm silicon oxide, and the 100 nm neodymium oxide is 10:2:1.

[0058] The polishing liquid preparation method is the same as that in Example 1.

[0059] Comparative Example 6:

[0060] A chemical mechanical polishing liquid for 440C stainless steel comprises silicon oxide, neodymium oxide, malic acid, 30% H2O2, polyvinyl alcohol, sorbitol, and deionized water. The silicon oxide comprises two particle sizes, 10 nm and 50 nm. The silicon oxide abrasive particles with a particle size of 10 nm account for 1-5 wt%, the silicon oxide abrasive particles with a particle size of 50 nm account for 0.2-2 wt%, the neodymium oxide abrasive particles with a particle size of 100 nm account for 0.1-0.3 wt%, the 30% H2O2 comprises 0.3-0.5 wt%, polyvinyl alcohol comprises 0.3-0.5 wt%, sorbitol comprises 0.1-0.3 wt%, and the balance is deionized water. The pH value is adjusted to 6.5 by malic acid, where the above wt% represents mass percentage. The mass ratio of the 10 nm silicon oxide, 50 nm silicon oxide, and 100 nm neodymium oxide is 12:3:1, and the mass ratio of the polyvinyl alcohol to sorbitol is 3:1.

[0061] The polishing liquid preparation method is the same as that in Example 1.

[0062] Comparative Example 7:

[0063] A chemical mechanical polishing liquid for 440C stainless steel comprises silicon oxide, neodymium oxide, malic acid, glycine, 30% H2O2, polyethylene glycol, polyvinyl alcohol, and deionized water. The silicon oxide comprises two particle sizes, 10 nm and 100 nm. The silicon oxide abrasive particles with a particle size of 10 nm account for 3-5 wt%, and the silicon oxide abrasive particles with a particle size of 100 nm account for 0.1-0.5 wt%. The neodymium oxide abrasive particles with a particle size of 20 nm account for 0.05-0.15 wt%. The 30% H2O2 accounts for 2-4 wt%. The polyethylene glycol accounts for 0.2-0.5 wt%. The polyvinyl alcohol accounts for 0.2-0.5 wt%. The balance is deionized water. The pH value is adjusted to 7 by malic acid. The above wt% represents mass percentage. The mass ratio of the 10 nm silicon oxide, the 100 nm silicon oxide, and the 20 nm neodymium oxide is 20:3:1. The mass ratio of the polyethylene glycol to the polyvinyl alcohol is 1:1.

[0064] The polishing liquid preparation method is the same as that in Example 1.

[0065] Comparative Example 8:

[0066] A chemical mechanical polishing liquid for 440C stainless steel comprises silicon oxide, neodymium oxide, malic acid, glycine, 30% H2O2, polyethylene glycol, sorbitol, and deionized water. The silicon oxide comprises two particle sizes, 50 nm and 100 nm. The 50 nm silicon oxide abrasive particles account for 3-5 wt %, the 100 nm silicon oxide abrasive particles account for 15-20 wt %, the 20 nm neodymium oxide abrasive particles account for 0.5-0.8 wt %, the 30% H2O2 accounts for 1-3 wt %, the polyethylene glycol accounts for 0.1-0.2 wt %, the polyvinyl alcohol accounts for 0.2-0.4 wt %, and the balance is deionized water. The pH value is adjusted to 5 by malic acid. The above wt % represents mass percentage. The mass ratio of the 50 nm silicon oxide, the 100 nm silicon oxide, and the 20 nm neodymium oxide is 6:30:1, and the mass ratio of the polyethylene glycol to the sorbitol is 1:2.

[0067] The polishing liquid preparation method is the same as that in Example 1.

[0068] The polishing liquids of Examples 1-3 and Comparative Examples 1-8 were used to polish 440C stainless steel. The results are shown in the following table and Figure 1-11 As shown:

[0069] Polishing results of 440C stainless steel using the polishing liquids of Examples 1-3 and Comparative Examples 1-8

[0070] Material removal rate (nm / min) Roughness (nm, Zygo) Corrosion pits (number) Example 1 84 0.284 0 Example 2 82 0.292 1 Example 3 82 0.299 1 Comparative Example 1 89 0.359 2 Comparative Example 2 90 0.501 11 Comparative Example 3 86 0.434 9 Comparative Example 4 85 0.332 3 Comparative Example 5 92 0.317 4 Comparative Example 6 87 0.384 5 Comparative Example 7 83 0.412 8 Comparative Example 8 91 0.559 18

[0071] Combined with the above table and Figure 1-10 It can be seen that the results of Examples 1-3 and Comparative Examples 1-4 show that the polishing effect of the abrasive particles of the mixed components of silicon oxide and neodymium oxide is significantly higher than that of the abrasive particles of a single component; the results of Examples 1-3 and Comparative Examples 5-6 show that the particle size of each component in the mixed abrasive particles has a certain influence on the polishing effect, and the effect of the polishing liquid prepared by the abrasive particle size of Examples 1-3 is significantly better than the effect of the polishing liquid prepared by the abrasive particles with a larger particle size; the results of Examples 1-3 and Comparative Example 7 show that when the proportion of silicon oxide abrasive particles is low, the effect of the polishing liquid prepared is significantly reduced; the results of Examples 1-3 and Comparative Example 8 show that when the proportion of silicon oxide abrasive particles is high, the effect of the polishing liquid prepared is also significantly reduced.

[0072] In summary, the present invention significantly improves the chemical softening effect and mechanical removal efficiency of 440C stainless steel by preparing a polishing liquid by mixing two abrasives, silicon oxide and neodymium oxide. Moreover, under the action of the polishing liquid with an optimized formula, the surface damage of 440C stainless steel is effectively reduced, and the polishing roughness can reach a level below 0.3nm, realizing the processing of the near-atomic level surface of 440C stainless steel.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A chemical mechanical polishing liquid for 440C stainless steel, characterized in that: including abrasive particles, pH adjusting agent, oxidizing agent, dispersant and deionized water; The abrasive particles are a mixture of silicon oxide and neodymium oxide, the mass ratio of the silicon oxide to the neodymium oxide is (25-30):1, the particle size of the silicon oxide is in the range of 10-100 nm, and the particle size of the neodymium oxide is in the range of 20-50 nm; The pH adjusting agent is at least one of oxalic acid, malic acid, and glycine; The oxidant is H2O2; The dispersant is at least one of polyethylene glycol, polyvinyl alcohol, and sorbitol; The pH value of the polishing liquid is 3-7.

2. The chemical mechanical polishing liquid for 440C stainless steel according to claim 1, characterized in that: Calculated in terms of mass percentage, the mass of the abrasive particles is 0.5% to 25% of the total mass of the polishing liquid, the mass of the oxidant is 0.5% to 5% of the total mass of the polishing liquid, the mass of the dispersant is 0.02% to 2% of the total mass of the polishing liquid, and the remainder is the deionized water and the pH adjusting agent.

3. A method for preparing a chemical mechanical polishing liquid for 440C stainless steel according to claim 1, characterized in that: The method comprises the following steps: mixing abrasive grains, a pH adjusting agent, an oxidant, a dispersant and deionized water in the following mass proportions to prepare the polishing liquid, wherein the mass proportion of the abrasive grains in the polishing liquid is 0.5-25wt%, the mass proportion of the oxidant in the polishing liquid is 0.5-5wt%, the mass proportion of the dispersant in the polishing liquid is 0.02-2wt%, and the rest are the deionized water and the pH adjusting agent.

4. The method for preparing a chemical mechanical polishing liquid for 440C stainless steel according to claim 3, characterized in that: First, the silicon oxide and the neodymium oxide are mixed in proportion, and then the oxidant, the dispersant and the deionized water are added in sequence and stirred evenly. Then, the pH adjusting agent is added and the pH is adjusted to 3-7 to obtain the polishing liquid.

5. The method for preparing a chemical mechanical polishing liquid for 440C stainless steel according to claim 4, characterized in that: The mass ratio of the silicon oxide to the neodymium oxide is (25-30):1.

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