An intelligent lubricant for titanium alloy cutting and its preparation method

Abstract

The present invention discloses an intelligent lubricant for titanium alloy cutting and its preparation method, specifically a poly(N-isopropylacrylamide-co-acrylic acid)-molybdenum disulfide / graphene oxide intelligent lubricant used in the process of titanium alloy machining and its preparation method. The preparation steps include: first, preparing inorganic fullerene-like molybdenum disulfide and compounding it with graphene oxide to prepare an aqueous solution of molybdenum disulfide / graphene oxide; secondly, preparing poly(N-isopropylacrylamide-co-acrylic acid) composite microspheres by aqueous solution polymerization method; finally, compounding the poly(N-isopropylacrylamide-co-acrylic acid) composite microspheres with the aqueous solution of molybdenum disulfide / graphene oxide to prepare the intelligent lubricant. The present invention is simple and effective. The prepared intelligent lubricant has good dispersibility, can achieve intelligent lubrication response based on temperature and pH, has good lubrication performance when used in titanium alloy / cemented carbide friction pairs, and has good application prospects in the fields such as titanium alloy machining.

Description

Technical Field

[0001] The invention relates to the field of mechanical processing lubricants, and in particular to an intelligent lubricant for titanium alloy cutting and a preparation method thereof. The lubricant can achieve intelligent lubrication through temperature and pH response. Background Art

[0002] Titanium alloys have significant advantages such as high specific strength, good corrosion resistance and high thermal stability, and have been widely used in aerospace, marine, energy, chemical and biomedical fields. With the development of society, the global demand for titanium alloy materials is increasing day by day. However, there are problems such as small deformation coefficient, high cutting temperature and large cutting force in the cutting process of titanium alloys. Especially in the long-term cutting process, as the friction temperature increases, the cutting fluid degrades and acidifies, resulting in a significant decrease in the lubrication performance of conventional cutting fluids, severe tool wear, and serious restrictions on the machining accuracy and efficiency of titanium alloys. Studies have shown that reducing the friction coefficient between titanium alloys and cutting tools and preventing excessive tool wear are the key to ensuring the machining accuracy and efficiency of titanium alloys. Therefore, how to achieve efficient lubrication in the machining process of titanium alloys has become an important issue that needs to be solved urgently, especially in the continuous cutting process of titanium alloys. The problem of insufficient lubrication performance caused by increasing temperature and decreasing pH needs to be solved urgently.

[0003] Nano-molybdenum disulfide and graphene oxide are common nano-lubricants and are widely used in various mechanical processing fields. However, the surface energy of both is high and they are prone to agglomeration, which has become a technical bottleneck that affects the lubrication performance advantages of nano-lubricants. Polymer microgels are a type of nano-microsphere smart materials with a three-dimensional network structure. They can produce significant responses to environmental changes such as temperature and have good dispersibility in water. They have been widely used in drug release, sewage treatment, switch valves and other fields, and also play an increasingly important role in the lubrication field. Therefore, if the advantages of polymer microgels and molybdenum disulfide / graphene oxide are combined, it is expected to develop a new type of smart lubricant for titanium alloy processing, which can produce smart lubrication response according to environmental changes. However, the combination mode, structural composition and preparation method of the composite material will have unpredictable effects on its lubrication performance. So far, there has been no report on such a titanium alloy processing smart lubricant and its preparation method that can simultaneously achieve temperature and pH control and load nano-lubricants. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an intelligent lubricant for titanium alloy cutting for friction reduction and lubrication in the titanium alloy cutting process in view of the shortcomings of the prior art. The lubricant can achieve intelligent lubrication based on the response to temperature and pH during the cutting process, thereby reducing friction and wear and improving the surface quality of the titanium alloy.

[0005] The present invention is realized through the following specific technical solutions:

[0006] An intelligent lubricant for titanium alloy cutting processing, whose chemical structure composition is: poly(N-isopropylacrylamide-co-acrylic acid)-molybdenum disulfide / graphene oxide; wherein polyacrylic acid and poly-N-isopropylacrylamide form a three-dimensional interpenetrating network structure composite microsphere with a particle size of 400-700 nm, molybdenum disulfide has an inorganic fullerene-like structure, and is adsorbed on the surface of graphene oxide nanosheets together with the composite microsphere; the mass ratio of poly-N-isopropylacrylamide to polyacrylic acid is 8-9:1, the mass ratio of the composite microsphere to graphene oxide and molybdenum disulfide is 1500-5000:30-50:1, and the particle size of molybdenum disulfide is 50-80 nm.

[0007] This intelligent lubricant is prepared according to the following method:

[0008] (1) Take 1.0-2.3 g of thioacetamide, 0.5-1.0 g of sodium molybdate, and 80-160 mL of deionized water and add them to a three-necked flask with a reflux device in sequence. Stir at 300 r / min and heat to 79-81 °C, add 7-15 mL of absolute ethanol and continue heating and stirring. When the temperature reaches 82-84 °C, add 15-30 mL of concentrated hydrochloric acid with a mass concentration of 36-38%, keep warm and stir for 10-15 min, filter the reaction product and wash it with water until neutral, then dry it at 110-120 °C, calcine it at 480-500 °C and keep warm for 60-65 min, and finally grind it to obtain inorganic fullerene-like structure molybdenum disulfide;

[0009] (2) Configure the molybdenum disulfide prepared in step (1) into an aqueous solution with a concentration of 0.05 g / L, mix it with an aqueous solution of graphene oxide with a concentration of 2 g / L, and the volume ratio is 0.75-1.25:1. Stir magnetically at a rate of 200-300 r / min for 20-40 min and then ultrasonicate for 50-60 min, where the ultrasonic power is 200-400 W, to obtain an aqueous solution of molybdenum disulfide / graphene oxide;

[0010] (3) Take 1.6-3.6 g of N-isopropylacrylamide, 0.2-0.4 g of acrylic acid, 0.033-0.066 g of N,N'-methylenebisacrylamide, 0.02-0.04 g of sodium dodecyl sulfate, and 120-250 mL of deionized water and add them to a three-necked flask in sequence. Then introduce nitrogen to remove the oxygen in the solution, stir magnetically at a rate of 450-550 r / min for 50-55 min and then start heating. When the temperature reaches 67-70 °C, slowly add 10-20 mL of a potassium persulfate solution with a concentration of 0.0080-0.0085 g / mL to the three-necked flask, and finally react at 67-70 °C for 5-5.5 h;

[0011] (4) Dialyze the solution after the reaction in step (3) with deionized water. During the dialysis process, use magnetic stirring to accelerate the dialysis rate, change the deionized water every 8 - 10 h, and dialyze for 6 - 7 d to obtain poly(N - isopropylacrylamide - co - acrylic acid) composite microspheres.

[0012] (5) After adjusting the concentration of the poly(N - isopropylacrylamide - co - acrylic acid) composite microspheres prepared in step (4) to 1.0 wt%, mix and process it with the molybdenum disulfide / graphene oxide aqueous solution prepared in step (2). Carry out magnetic stirring at a rate of 200 - 260 r / min for 25 - 35 min, then ultrasonic for 1.5 - 2 h, where the ultrasonic power is 300 - 400 W. Finally, stir for 7 - 8 h and centrifuge at high speed to obtain the intelligent lubricant.

[0013] Among them, in step (3), the mass ratio of N - isopropylacrylamide to acrylic acid is 8 - 9:1, and in step (5), the mass ratio of the poly(N - isopropylacrylamide - co - acrylic acid) composite microspheres to graphene oxide is 50 - 100:1.

[0014] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0015] (1) The present invention adopts a specific reaction raw material ratio and preparation process. First, inorganic fullerene - like molybdenum disulfide is dispersed on the surface of graphene oxide nanosheets, and then the poly(N - isopropylacrylamide - co - acrylic acid) composite microspheres are adsorbed on the surface of graphene oxide nanosheets again through surface hydrogen bonds, solving the agglomeration problem of nano - molybdenum disulfide and graphene oxide. The obtained poly(N - isopropylacrylamide - co - acrylic acid) - molybdenum disulfide / graphene oxide intelligent lubricant has good aqueous solution dispersibility and a significantly increased stable time.

[0016] (2) The intelligent lubricant prepared by the present invention has a uniform and controllable particle size distribution, can make a rapid response to enhance the lubrication performance with the increase of temperature or the decrease of pH, and has an intelligent lubrication effect.

[0017] (3) The components of the intelligent lubricant prepared by the present invention have a synergistic lubrication effect, and have a significant friction reduction effect and surface processing quality compared with single raw materials. The average friction coefficient is reduced by more than 20%.

[0018] (4) The preparation method of the present invention has a simple process, low cost, mild preparation conditions, can realize the controllable preparation of the intelligent lubricant, and is easy to be applied on a large scale. Description of the Drawings

[0019] Figure 1Comparison of appearance photos of the intelligent lubricant prepared in Example 1 before and after storage at different temperatures for 30 days: (a) newly prepared, 25 °C, (b) newly prepared, 35 °C, (c) stored for 30 days, 25 °C, (d) stored for 30 days, 35 °C.

[0020] Figure 2 Comparison of average particle size and dispersity index of the intelligent lubricant prepared in Example 1 before and after storage at different temperatures for 30 days: (a) 25 °C, (b) 35 °C.

[0021] Figure 3 Transmission electron micrograph (a) and structural schematic diagram (b) of the intelligent lubricant prepared in Example 1.

[0022] Figure 4 Curve graph of the particle size of the intelligent lubricant prepared in Example 1 varying with temperature and pH.

[0023] Figure 5 Friction coefficient comparison graph of the intelligent lubricant prepared in Example 1. Detailed implementation mode

[0024] The present invention will be further described below in conjunction with specific embodiments. The embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0025] Example 1

[0026] (1) Take 1.0 g of thioacetamide, 0.5 g of sodium molybdate, and 80 mL of deionized water and add them successively to a three-necked flask equipped with a reflux device. Stir at 300 r / min and heat to 80 °C. Add 7.5 mL of absolute ethanol and continue heating and stirring. When the temperature reaches 82 °C, add 15 mL of concentrated hydrochloric acid with a mass concentration of 36 - 38%. Keep warm and stir the reaction for 15 min. Filter the reaction product and wash it with water until neutral. Then dry it at 110 °C and calcine it at 480 °C for 60 min. Finally, grind it to obtain inorganic fullerene-structured molybdenum disulfide;

[0027] (2) Configure the molybdenum disulfide prepared in step (1) into an aqueous solution with a concentration of 0.05 g / L, mix it with an aqueous solution of graphene oxide with a concentration of 2 g / L, with a volume ratio of 1:1. Magnetically stir at a rate of 260 r / min for 20 min and then ultrasonicate for 60 min, where the ultrasonic power is 300 W, to obtain an aqueous solution of molybdenum disulfide / graphene oxide;

[0028] (3) 1.7 g of N-isopropylacrylamide, 0.2 g of acrylic acid, 0.033 g of N,N'-methylenebisacrylamide, 0.02 g of sodium dodecyl sulfate, and 120 mL of deionized water were successively added to a three-necked flask. Subsequently, nitrogen was introduced to remove the oxygen in the solution. Magnetic stirring was carried out at a rate of 500 r / min for 50 min, and then the temperature was raised. When the temperature reached 70 °C, 10 mL of a potassium persulfate solution with a concentration of 0.0083 g / mL was slowly added to the three-necked flask. Finally, the reaction was carried out at 70 °C for 5 h;

[0029] (4) The solution after the reaction in step (3) was subjected to dialysis treatment with deionized water. During the dialysis process, magnetic stirring was used to accelerate the dialysis rate, and the deionized water was changed every 8 h. Dialysis was carried out for 7 d to obtain poly(N-isopropylacrylamide-co-acrylic acid) composite microspheres;

[0030] (5) After adjusting the concentration of the poly(N-isopropylacrylamide-co-acrylic acid) composite microspheres prepared in step (4) to 1.0 wt%, it was mixed with the molybdenum disulfide / graphene oxide aqueous solution prepared in step (2). The mass ratio of the poly(N-isopropylacrylamide-co-acrylic acid) composite microspheres to graphene oxide was 50:1. Magnetic stirring was carried out at a rate of 200 r / min for 30 min, followed by ultrasonic treatment for 2 h with an ultrasonic power of 400 W. Finally, stirring was carried out for 8 h, and then high-speed centrifugation was carried out to obtain the intelligent lubricant.

[0031] To test the intelligent lubrication performance of the present invention, a ball-on-disk reciprocating friction tester was used. The friction pair materials were a TC4 disk and a YG8 ball. The friction test parameters were: load 15 N, single stroke 5 mm, reciprocating motion frequency 5 Hz, test time 10 min, temperature 25, 30, 32, 35 °C, pH 3, 5, 7, 9, and concentration 0.25, 0.5, 0.75, 1.0 wt%.

[0032] From Figure 1 、 Figure 2 It can be seen that the poly(N-isopropylacrylamide-co-acrylic acid)-molybdenum disulfide / graphene oxide intelligent lubricant prepared in Example 1 has a dispersion stability time of up to 30 d, has obvious thermosensitive response characteristics, and the particle size and dispersion index slightly increase after long-term storage, without significantly affecting the intelligent lubricant.

[0033] From Figure 3 It can be seen that the molybdenum disulfide and poly(N-isopropylacrylamide-co-acrylic acid) composite microspheres prepared in Example 1 are co-adsorbed on the surface of graphene oxide nanosheets, and have good dispersion performance without obvious agglomeration.

[0034] From Figure 4It can be seen that the poly(N-isopropylacrylamide-co-acrylic acid)-molybdenum disulfide / graphene oxide intelligent lubricant prepared in Example 1 is sensitive to both temperature and pH. As the temperature increases, the particle size gradually decreases, and the rate of decrease is the largest near 32 °C. As the pH increases, the particle size gradually increases, showing a linear increasing trend.

[0035] From Figure 5 It can be seen that each component of the poly(N-isopropylacrylamide-co-acrylic acid)-molybdenum disulfide / graphene oxide intelligent lubricant prepared in Example 1 has a synergistic lubrication effect, has a lower friction coefficient compared with single raw materials, and the lubrication performance of titanium alloy is significantly improved.

[0036] Taking the friction coefficient as the response index, temperature 25, 30, 32, 35 °C, concentration 0.25, 0.5, 0.75, 1.0 wt%, and pH 3, pH 5, pH 7, pH 9 were selected to conduct a three-factor and four-level orthogonal experiment to explore the effects of temperature, concentration, and pH on the lubrication performance of the intelligent lubricant. The range analysis results are shown in Table 1.

[0037] Table 1 Range analysis table of friction experiment results

[0038]

[0039] In the table, k1, k2, k3, and k4 respectively represent the sum of the friction coefficients corresponding to the levels 1, 2, 3, and 4 of temperature and pH, K1, K2, K3, and K4 respectively represent the average values of the friction coefficients corresponding to the levels of each factor, and R represents the range of this level in each column. The larger the R value, the greater the influence of the factor being investigated on the investigated index. The data in Table 1 show that temperature, concentration, and pH all have a greater impact on the lubrication performance of the intelligent lubricant, and intelligent lubrication can be achieved by regulating the temperature and pH of the lubricant.

Claims

1. An intelligent lubricant for titanium alloy cutting, characterized in that, The chemical structure is: poly(N-isopropylacrylamide-co-acrylic acid)-molybdenum disulfide / graphene oxide; wherein polyacrylic acid and poly-N-isopropylacrylamide form a three-dimensional interpenetrating network structure composite microsphere with a particle size of 400-700 nm. Molybdenum disulfide has an inorganic fullerene-like structure and is adsorbed on the surface of graphene oxide nanosheets together with the composite microspheres; the particle size of molybdenum disulfide is 50-80 nm; The preparation method of the intelligent lubricant includes the following steps: (1) Take 1.0 g of thioacetamide, 0.5 g of sodium molybdate, and 80 mL of deionized water and add them to a three-necked flask equipped with a reflux device. Stir at 300 r / min and heat to 80 °C. Add 7.5 mL of absolute ethanol and continue heating and stirring. When the temperature reaches 82 °C, add 15 mL of concentrated hydrochloric acid with a mass concentration of 36-38%. Keep the temperature and stir for 15 min. Filter the reaction product and wash it with water until neutral. Then dry it at 110 °C, calcine it at 480 °C and keep it for 60 min. Finally, grind it to obtain molybdenum disulfide with an inorganic fullerene-like structure; (2) Prepare an aqueous solution of molybdenum disulfide prepared in step (1) with a concentration of 0.05 g / L, and mix it with an aqueous solution of graphene oxide with a concentration of 2 g / L. The volume ratio is 1:

1. Magnetically stir at a rate of 260 r / min for 20 min and then sonicate for 60 min. The sonication power is 300 W to obtain an aqueous solution of molybdenum disulfide / graphene oxide; (3) Take 1.7 g of N-isopropylacrylamide, 0.2 g of acrylic acid, 0.033 g of N,N'-methylenebisacrylamide, 0.02 g of sodium dodecyl sulfate, and 120 mL of deionized water and add them to a three-necked flask in sequence. Then introduce nitrogen to remove the oxygen in the solution. Magnetically stir at a rate of 500 r / min for 50 min and then start heating up. When the temperature reaches 70 °C, slowly add 10 mL of a potassium persulfate solution with a concentration of 0.0083 g / mL to the three-necked flask. Finally, react at 70 °C for 5 h; (4) Dialyze the solution after the reaction in step (3) with deionized water. Use magnetic stirring during the dialysis process to accelerate the dialysis speed. Replace the deionized water every 8 h and dialyze for 7 d to obtain poly(N-isopropylacrylamide-co-acrylic acid) composite microspheres; (5) After adjusting the concentration of the poly(N-isopropylacrylamide-co-acrylic acid) composite microspheres prepared in step (4) to 1.0 wt%, mix it with the aqueous solution of molybdenum disulfide / graphene oxide prepared in step (2). The mass ratio of the poly(N-isopropylacrylamide-co-acrylic acid) composite microspheres to graphene oxide is 50:

1. Magnetically stir at a rate of 200 r / min for 30 min and then sonicate for 2 h. The sonication power is 400 W. Finally, stir for 8 h and centrifuge at high speed to obtain the intelligent lubricant.

Images