阅读说明：本技术 一种发动机缸孔内壁自润滑涂层及其制备方法 (Self-lubricating coating for inner wall of engine cylinder hole and preparation method thereof ) 是由 黄太红 谭贤兵 宋鹏 雷基林 邓伟 万发扬 陈榕 吕建国 郑必举 于 2021-07-21 设计创作，主要内容包括：本发明属于发动机涂层技术领域,具体公开了一种发动机缸孔内壁自润滑涂层及其制备方法,涂层的原料,按质量占比计,包括30％～40％的氧化锆增韧氧化铝粉末以及Fe基合金粉末,所述Fe基合金粉末呈球形,且粉末粒径范围为5～30μm。制备方法为,将Fe基合金粉末与氧化锆增韧氧化铝粉末放入球磨机进行球磨,使两者混合均匀；再将混合粉末通过等离子喷涂技术,喷涂到铝合金气缸的缸孔内壁上,得到涂层。采用本发明的方案,解决了目前有机涂层在低温环境下脆性大,涂层易开裂和脱落的问题；而采用缸体镶嵌缸套的方式,又使得长时间高温环境工作,两者之间的连接强度下降,导致服役寿命缩短的问题。(The invention belongs to the technical field of engine coatings, and particularly discloses a self-lubricating coating for the inner wall of an engine cylinder hole and a preparation method thereof, wherein the raw materials of the coating comprise 30-40% of zirconia toughened alumina powder and Fe-based alloy powder in percentage by mass, the Fe-based alloy powder is spherical, and the particle size range of the powder is 5-30 mu m. The preparation method comprises the steps of putting Fe-based alloy powder and zirconia toughened alumina powder into a ball mill for ball milling, and uniformly mixing the Fe-based alloy powder and the zirconia toughened alumina powder; and spraying the mixed powder onto the inner wall of the cylinder hole of the aluminum alloy cylinder by a plasma spraying technology to obtain a coating. By adopting the scheme of the invention, the problems that the existing organic coating has large brittleness in a low-temperature environment and the coating is easy to crack and fall off are solved; and the mode that the cylinder sleeve is inlaid in the cylinder body is adopted, so that the long-time high-temperature environment works, the connection strength between the cylinder body and the cylinder sleeve is reduced, and the service life is shortened.)

1. The utility model provides an engine cylinder hole inner wall self-lubricating coating which characterized in that: the raw materials of the coating comprise 30-40% of zirconia toughening alumina powder and Fe-based alloy powder by mass, wherein the Fe-based alloy powder is spherical, and the particle size range of the powder is 5-30 mu m.

2. The engine cylinder bore inner wall self-lubricating coating of claim 1, wherein: the alumina matrix powder in the zirconia-toughened alumina powder is irregular and has a powder particle size range of 20-30 mu m, and the zirconia and the alumina in the zirconia-toughened alumina powder exist in the powder in a eutectic structure form and have a powder particle size range of 25-30 mu m.

3. A method of preparing the engine cylinder bore inner wall self-lubricating coating of claim 1, characterized in that: the method comprises the following steps:

step 1: putting Fe-based alloy powder and zirconia toughened alumina powder into a ball mill for ball milling, and uniformly mixing the Fe-based alloy powder and the zirconia toughened alumina powder;

step 2: and (3) spraying the mixed powder obtained in the step (1) onto the inner wall of a cylinder hole of an aluminum alloy cylinder by a plasma spraying technology to obtain a coating.

4. The method for preparing the self-lubricating coating on the inner wall of the engine cylinder hole according to claim 3, wherein the self-lubricating coating is prepared by the following steps: in the step 1, before ball milling, the Fe-based alloy powder and the zirconia toughened alumina powder are dried.

5. The method for preparing the self-lubricating coating on the inner wall of the engine cylinder hole according to claim 3, wherein the self-lubricating coating is prepared by the following steps: the spraying parameters in the step 2 are as follows: the current is 300-400A, the voltage is 50-55V, the spraying distance is 30-40 mm, the rotating speed is 100-200 r/min, the air draft speed is 10-20 m/s, the powder feeding speed is 100-120 g/min, and the spraying angle is 45 degrees.

Technical Field

The invention belongs to the technical field of engine coatings, and particularly relates to a self-lubricating coating for an inner wall of an engine cylinder hole and a preparation method thereof.

Background

In extremely cold regions, such as northern China and polar region investigation regions, the friction coefficient of lubricating oil in the engine is relatively large due to low-temperature solidification of the lubricating oil, so that the engine is difficult to start. At present, foreign scholars aim at the problem and mainly solve the problem in two ways, namely, the low-temperature resistance of the lubricating fluid is enhanced; in addition, the friction force of the inner wall of the cylinder is reduced by changing the material of the cylinder, and aiming at the second mode, the most economical and common mode at present is to coat the low-temperature-resistant organic coating on the inner wall of the cylinder, but the brittleness of the organic coating is increased due to the low-temperature environment, so that the coating is easy to crack and fall off.

In addition, because the whole cylinder of the engine commonly seen in the market at present is formed by cast iron through die casting, although the wear resistance of the engine can meet the requirement, the manufacturing cost is high, the mass is large, the weight of the whole engine is increased, and the energy consumption is increased; the whole size of the casting is large, and the shape is complex; the shrinkage porosity and the shrinkage cavity are difficult to control in the die-casting process, and the defects of cold shut and the like caused by insufficient casting of a casting are easy to generate.

Therefore, in order to improve the wear resistance and reduce the weight of the engine, the common solution at present is to adopt an aluminum alloy engine cylinder body, which obviously reduces the quality of the engine, and to inlay a cast iron cylinder sleeve in the cylinder body to ensure the wear resistance of the inner wall in contact with lubricating oil, but because the thermal expansion coefficient difference between the aluminum alloy and the cast iron is large, namely the deformation degree between the cylinder body and the cylinder sleeve is different in the long-term high-temperature working process, and the inlay is in mechanical connection, the cylinder sleeve is easy to separate from the cylinder body and the cylinder sleeve, and the connection strength is reduced, so the service life of the prepared cylinder sleeve is short.

Based on the above, the application provides a self-lubricating coating for the inner wall of the cylinder hole of the engine and a preparation method thereof, which are used for solving the problems that the existing organic coating is high in brittleness in a low-temperature environment and the coating is easy to crack and fall off; and the mode that the cylinder sleeve is inlaid in the cylinder body is adopted, so that the long-time high-temperature environment works, the connection strength between the cylinder body and the cylinder sleeve is reduced, and the service life is shortened.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a self-lubricating coating for the inner wall of an engine cylinder hole and a preparation method thereof, aiming at solving the problems that the existing organic coating has large brittleness in a low-temperature environment and the coating is easy to crack and fall off; and the mode that the cylinder sleeve is inlaid in the cylinder body is adopted, so that the long-time high-temperature environment works, the connection strength between the cylinder body and the cylinder sleeve is reduced, and the service life is shortened.

In order to achieve the purpose, the invention adopts the following technical scheme:

the raw materials of the coating comprise 30-40% of zirconia toughening alumina powder and Fe-based alloy powder by mass, wherein the Fe-based alloy powder is spherical, and the particle size of the powder is 5-30 mu m.

Compared with the prior art, the invention has the following beneficial effects:

1. experiments prove that the friction coefficient of the aluminum alloy cylinder body inlaid cast iron cylinder sleeve reaches above 0.5 under the dry friction condition (extremely cold environment and lubricating oil solidification) of the coating, the friction coefficient of the coating provided by the scheme is stably kept at about 0.1, and the self-lubricating effect under the lubricating oil solidification condition is realized.

2. In the scheme, the formed Fe-based alloy coating has a lower friction coefficient, the wear resistance is superior to that of the traditional grey cast iron, the wear resistance and the corrosion resistance are good, and in addition, the Fe-based alloy coating has similar chemical components with most mechanical parts and good bonding performance and can be applied to various engine cylinder holes.

Furthermore, the alumina matrix powder in the zirconia-toughened alumina powder is irregular in shape and has a powder particle size range of 20-30 μm, and the zirconia and the alumina in the zirconia-toughened alumina powder exist in the powder in a eutectic structure form and have a powder particle size range of 25-30 μm.

Has the advantages that: therefore, the requirements of the spraying process can be met, the ceramic particles can be uniformly distributed in the coating, and the self-lubricating effect of the ceramic particles is ensured.

The invention also discloses a preparation method of the self-lubricating coating on the inner wall of the engine cylinder hole, which comprises the following steps:

step 1: putting Fe-based alloy powder and zirconia toughened alumina powder into a ball mill for ball milling, and uniformly mixing the Fe-based alloy powder and the zirconia toughened alumina powder;

step 2: and (3) spraying the mixed powder obtained in the step (1) onto the inner wall of a cylinder hole of an aluminum alloy cylinder by a plasma spraying technology to obtain a coating.

Has the advantages that: 1. this scheme of adoption adopts plasma spraying preparation one deck to have the coating of self-lubricating in cylinder inside can be fine improve the engine and be difficult to the problem of starting in extremely cold area. The self-lubricating coating can reduce friction force, can be fine bear impact load for the engine, reduce the inside destruction of engine and the consumption of energy, and the tie coat that contains wherein can provide sufficient toughness to protect the cylinder body and prolong the life-span, utilize plasma spraying to prepare compact structure in addition, the even coating of composition.

2. In the scheme, the zirconia toughened alumina powder is uniformly dispersed in the Fe-based alloy coating in the spraying process, so that the coating can be ensured to have higher comprehensive performance of the Fe-based alloy, and can also have higher wear resistance and higher hardness by adding the zirconia toughened alumina powder; and the zirconia toughened alumina can be used as a hard second phase to prevent dislocation movement and prevent premature deformation failure. Therefore, when the engine is started in an extremely cold area, the friction force can be obviously reduced and larger impact load can be dispersed, so that the service life of the cylinder is greatly prolonged, and particularly, the cylinder has a good self-lubricating effect under the condition that lubricating liquid is frozen.

Further, in the step 1, before ball milling, the Fe-based alloy powder and the zirconia toughened alumina powder are dried.

Has the advantages that: thus, the two kinds of powder can be fully and uniformly mixed during ball milling.

Further, the spraying parameters in the step 2 are as follows: the current is 300-400A, the voltage is 50-55V, the spraying distance is 30-40 mm, the rotating speed is 100-200 r/min, the air draft speed is 10-20 m/s, the powder feeding speed is 100-120 g/min, and the spraying angle is 45 degrees.

Has the advantages that: experiments prove that the plasma spraying parameters provided by the scheme can obtain a coating with uniform tissue distribution, and the binding force between the coating and the inner wall of the engine cylinder hole is high.

Drawings

FIG. 1 is a microscopic topography of the coating of example 1 of the present invention at a 1mm scale after frictional wear in the absence of lubricating oil.

FIG. 2 is a microscopic morphology of the coating of example 1 of the present invention at the 300 μm scale after frictional wear in the absence of lubricating oil.

FIG. 3 is a microscopic morphology of 500 μm after frictional wear of the coating layer in example 1 of the present invention under the condition of adding lubricating oil.

FIG. 4 is a microstructure of the coating of example 1 of the present invention after frictional wear with lubricating oil at 100 μm.

FIG. 5 is a three-dimensional topography of the control group 2 of the present invention after frictional wear without adding lubricating oil.

FIG. 6 is a three-dimensional topography of the coating of example 1 after frictional wear without the addition of lubricating oil.

FIG. 7 is a three-dimensional topography of the control group 2 of the present invention after frictional wear under the condition of adding lubricating oil.

FIG. 8 is a three-dimensional topography of the coating of example 1 after frictional wear with lubricating oil.

FIG. 9 is a graph showing the change with time of the friction coefficient obtained by the frictional wear in the presence of a lubricating oil in example 1, comparative group 1 and comparative group 2 of the present invention.

FIG. 10 is a graph showing the change with time of the friction coefficient obtained by the frictional wear in the absence of lubricating oil in example 1 of the present invention, control 1 and control 2.

Detailed Description

The invention is further described in detail below with reference to the accompanying drawings, and specific embodiments are given.

Example 1:

a self-lubricating coating for the inner wall of an engine cylinder hole comprises 30% of ZTA (zirconia toughened alumina) powder and 70% of Fe-based alloy powder by mass, wherein the alumina matrix powder in the ZTA powder is in a random shape, the particle size of the powder is 20-30 mu m, the zirconia and the alumina in the ZTA powder exist in the powder in a eutectic structure form, the particle size of the powder is 25-30 mu m, the Fe-based alloy powder is spherical, and the particle size of the powder is 5-30 mu m.

The compositions of the Fe-based alloy powders in this example are shown in table 1 below.

TABLE 1 is a composition table of Fe-based alloy powders

The preparation process of the self-lubricating coating on the inner wall of the engine cylinder hole comprises the following steps:

step 1: drying the Fe-based alloy powder and 30 mass percent of ZTA (zirconium oxide toughened aluminum oxide) powder, and then putting the dried Fe-based alloy powder and the ZTA powder into a ball mill for full ball milling to uniformly mix the two powders.

Step 2: and (3) spraying the mixed powder obtained in the step (1) on the inner wall of a cylinder hole of the aluminum alloy cylinder by a plasma spraying technology, and feeding the powder in a single way to obtain a coating. The spray parameters are shown in table 2 below:

table 2 shows the spray parameters in step 2 of example 1

Example 2 to example 5:

the differences from example 1 are that the mass ratio of the raw materials is different in examples 2 to 5, and the following table 3 specifically shows.

Table 3 shows the raw materials used for the coatings of examples 2 to 5

	Example 2	Example 3	Example 4	Example 5
					Fe-based alloy powder	68％	65％	63％	60％
ZTA powder	32％	35％	37％	40％

Example 6:

the difference from example 1 is that the spraying parameters in step 2 of example 6 are different, as shown in table 4 below.

Table 4 shows the spray parameters in step 2 of example 6

Example 7:

the difference from example 1 is that the spraying parameters in step 2 of example 7 are different, as shown in table 5 below.

Table 5 shows the spray parameters in step 2 of example 7

Control group 1:

the difference from the embodiment 1 is that the cylinder body in the comparison group 1 is made of aluminum alloy, and a cast iron cylinder sleeve is inlaid in the cylinder body.

Control group 2:

the difference from example 1 is that ZTA powder was not added to the raw material of the coating layer in control 2.

And (3) testing:

the coated samples obtained using the protocols provided in examples 1 to 7 and the control were subjected to a frictional wear test:

the samples provided in examples 1 to 7 and control groups 1 and 2 were subjected to a frictional wear test in the absence of lubricating oil and with lubricating oil, respectively, using a CETR UMT-3 (China) as a wear apparatus, with an applied stress of 40N, a frictional displacement of 5mm, a frequency of 3Hz, and a total number of cycles of 4500; taking example 1 as an example:

wherein FIG. 1 is a microscopic topography at a 1mm scale after frictional wear of the coating in example 1 in the absence of lubricating oil;

FIG. 2 is a microscopic topography map of the coating of example 1 on the 300 μm scale after frictional wear in the absence of lubricating oil.

FIG. 3 is a microscopic morphology of 500 μm after frictional wear of the coating layer of example 1 under the condition of lubricating oil;

FIG. 4 is a microscopic topography of the coating of example 1 after frictional wear with lubricating oil at 100 μm.

It can be observed from fig. 1 to 4 that the coating surface after the frictional wear test was slightly scratched (furrowing) under the dry friction condition without lubricating oil, furrowing and abrasive dust were present in the wear zone after enlargement, and the scratching of the coating surface was not noticeable under the lubricating oil condition.

In addition, the three-dimensional surface analyzer is used for analyzing the three-dimensional appearance of scratches of the samples provided by the example 1 and the control group 2 after the friction wear test under two conditions, wherein fig. 5 is a three-dimensional appearance diagram of the control group 2 after friction wear without adding lubricating oil;

FIG. 6 is a three-dimensional topographical view of the coating layer of example 1 after frictional wear in the absence of lubricating oil;

FIG. 7 is a three-dimensional topography of the control group 2 after frictional wear with lubricating oil;

FIG. 8 is a three-dimensional topographical view of the coating of example 1 after frictional wear with lubricating oil.

From fig. 5 to 8, it can be seen that the scratch depth of the control 2 (without ZTA ceramic powder) reached 12.5 μm, whereas the scratch depth of the ZTA ceramic Fe-based alloy coating provided in example 1 was only 2.5 μm, and it was also observed that the scratch width of the surface of the control 2 was significantly wider than that of the example 1.

FIG. 9 is a graph showing the change with time of the friction coefficient obtained by the frictional wear in the presence of a lubricating oil in each of examples 1, 1 and 2, and FIG. 10 is a graph showing the change with time of the friction coefficient obtained by the frictional wear in the absence of a lubricating oil in each of examples 1, 1 and 2, and it can be observed that the maximum friction coefficient in the presence of a lubricating oil in each of controls 1, 2 and 1 is less than 0.1 in dry friction; however, in the absence of lubricating oil (i.e., it can be regarded as an extremely cold environment, and the lubricating oil solidifies), the maximum friction coefficients of the control group 1 and the control group 2 both exceed 0.5, while the friction coefficient of the coating of the example 1 is 0.1, and the coating of the example 1 maintains a stable state in the process, which indicates that the coating achieves the self-lubricating effect.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.