A crn-coated sharp-edged doctor blade ring and its coating preparation process

Abstract

The application relates to a CrN-coated sharp-head doctor blade ring and a coating preparation process thereof. Through a multi-arc ion plating technology, metal Cr is used as a target material, nitrogen is used as a reaction gas, a negative bias voltage is applied to a substrate after surface cleaning treatment, a current is applied to the Cr target, and a CrN coating is deposited on the surface of the substrate. The process is as follows: the surface of the doctor blade ring is cleaned and pretreated; the surface of the doctor blade ring is cleaned by IET; the doctor blade ring is bombarded for three times; the surface of the doctor blade ring is coated with CrN and a pure chromium layer through a multi-arc ion plating machine; after the CrN coating is completed, the temperature in the furnace of the multi-arc ion plating machine is reduced, and the doctor blade ring with the CrN coating is taken out. The CrN-coated sharp-head doctor blade ring and the coating preparation process thereof designed by the application greatly improve the bonding strength of the CrN coating, solve the problem of film layer peeling, do not perform sand blasting treatment before coating, effectively improve the film layer roughness, reduce the difficulty of subsequent processing, and improve the yield.

Description

Technical Field

[0001] This invention belongs to the field of piston ring technology, specifically relating to a CrN-coated pointed scraper ring and its coating preparation process. Background Technology

[0002] Piston rings are a key component of internal combustion engines. Currently, gasoline engines generally use a three-piece combination oil ring (one liner ring and two scraper rings). To improve mechanical performance, scraper rings need to undergo surface treatment. PVD treatment, with its advantages of high hardness, low coefficient of friction, corrosion resistance, and no pollution, is gradually replacing surface treatment methods such as chrome plating and gas nitriding. CrN coating, as a type of PVD treatment, has been widely used in scraper rings.

[0003] Currently, most scraper rings have a semi-circular head structure, making it relatively simple to coat with CrN coating, and the process is already mature. With the implementation of China VI emission standards, to improve the oil scraping performance of the scraper ring and reduce oil consumption, a pointed head structure has been adopted. Because of the large bending radius of the pointed head structure, the internal stress of the CrN coating also increases, making it prone to film peeling. A common solution is pre-coating sandblasting. Sandblasting can improve adhesion, but it cannot completely solve the problem of film peeling. Furthermore, sandblasting increases the roughness of the substrate, which in turn increases the roughness of the coating after coating, increasing the difficulty of subsequent processing. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a CrN-coated pointed scraper ring and its coating preparation process, which significantly improves the bonding strength of the CrN coating, solves the problem of film peeling, and eliminates the need for sandblasting before coating, effectively improving film roughness, reducing the difficulty of subsequent processing, and increasing the yield.

[0005] The technical solution of the present invention is as follows:

[0006] A CrN coating process using a pointed scraper ring includes a multi-arc ion plating machine. The process utilizes multi-arc ion plating technology, with metallic Cr as the target material and nitrogen as the reactant gas. A negative bias is applied to the surface-cleaned substrate, and a current is applied to the Cr target to deposit a CrN coating on the substrate surface. The multi-arc ion plating machine is divided into three groups of arc sources: a first group of chromium target arc sources, a second group of chromium target arc sources, and a third group of titanium target arc sources. The process steps are as follows:

[0007] Step 1: Clean and pre-treat the surface of the scraper ring;

[0008] Step 2: Perform I ET cleaning on the surface of the scraper ring, and turn on the multi-arc ion plating machine with a bias voltage of 100V, a frequency of 40HZ, and a duty cycle of 70%.

[0009] Step 3: The scraper ring is bombarded three times. During the first bombardment, the multi-arc ion plating machine is set to a bias voltage of 600V, a frequency of 40Hz, and a duty cycle of 70%. During the second bombardment, the multi-arc ion plating machine is set to a bias voltage of 800V, a frequency of 40Hz, and a duty cycle of 70%. During the third bombardment, the multi-arc ion plating machine is set to a bias voltage of 800V, a frequency of 40Hz, and a duty cycle of 70%.

[0010] Step 4: Apply a chromium layer to the surface of the scraper ring using a multi-arc ion plating machine, and then perform CrN plating;

[0011] Step 5: After the CrN coating is completed, lower the furnace temperature of the multi-arc ion plating machine and remove the scraper ring with the CrN coating.

[0012] Furthermore, the cleaning pretreatment in step 1 includes the following steps:

[0013] Step 11: The scraper ring is immersed in an alkaline solution for ultrasonic cleaning to remove oil stains;

[0014] Step 12: Remove rust and dry after two water washes;

[0015] Step 13: After the scraper ring has cooled, immerse it in a hydrocarbon solution for another cleaning;

[0016] Step 14: Dry the cleaned scraper ring by drying it with dryer or hot air.

[0017] Furthermore, after cleaning and pre-treatment of the scraper ring surface, the furnace of the multi-arc ion plating machine is evacuated, and water vapor in the furnace is removed at the same time, so that the vacuum degree in the furnace reaches below 0.005 Pa; after the vacuum degree in the furnace reaches below 0.005 Pa, heating is carried out to raise the furnace temperature to 380-400℃, while ensuring that the vacuum degree is below 0.007 Pa.

[0018] Furthermore, in step 2, the I ET cleaning is further specified as follows: argon gas is introduced into the furnace of the multi-arc ion plating machine, the bias voltage is turned on at 100V, the frequency is 40HZ, the duty cycle is 70%, the third set of titanium target arc sources is turned on, the arc current is 80-100A, and the cleaning time is 10-20 minutes.

[0019] Further, the first bombardment: Nitrogen gas is introduced into the furnace again, the multi-arc ion plating machine is turned on with a bias voltage of 600V, a frequency of 40HZ, and a duty cycle of 70%, the first set of chromium target arc sources is turned on, the arc current is 80-120A, the bombardment time is 120 seconds, the arc current is 80-120A, the bombardment time is 90-120 seconds, the first set of chromium rake arc sources is turned off, the second set of chromium rake arc sources is turned on, the arc current is 80-120A, the bombardment time is 90-120 seconds, the second set of chromium rake arc sources is turned off, the first bombardment ends, and there is a 120-second pause.

[0020] Second bombardment: Nitrogen gas is introduced into the furnace again. The multi-arc ion plating machine is set to a bias voltage of 800V, a frequency of 40Hz, and a duty cycle of 70%. The first set of chromium rake arc sources is turned on, with an arc current of 80-120A and a bombardment time of 90-120 seconds. The first set of chromium rake arc sources is turned off, and the second set of chromium rake arc sources is turned on, with an arc current of 80-120A and a bombardment time of 90 seconds. The second set of chromium rake arc sources is turned off, and the second bombardment ends. The process is paused for 110-120 seconds.

[0021] Third bombardment: Nitrogen gas is introduced into the furnace again. The multi-arc ion plating machine is set to a bias voltage of 800V, a frequency of 40Hz, and a duty cycle of 70%. The first set of chromium rake arc sources is turned on, with an arc current of 80-120A and a bombardment time of 90-120 seconds. The first set of chromium rake arc sources is then turned off. The second set of chromium rake arc sources is then turned on, with an arc current of 80-120A and a bombardment time of 90-120 seconds. The second set of chromium rake arc sources is then turned off. The third bombardment is then complete.

[0022] Furthermore, the specific process for applying a chromium layer to the surface of the scraper ring using a multi-arc ion plating machine is as follows: Argon gas is introduced, the bias voltage is turned on at 60V, the frequency is 40HZ, the duty cycle is 75%, the first and second groups of chromium rakes are turned on, the arc current is 180A, the coil current is 350mA, the electron collector is 40A, the furnace pressure is maintained at 2.65Pa, and the time is 1 hour.

[0023] Furthermore, the process of CrN coating on the surface of the scraper ring using a multi-arc ion plating machine is as follows: Nitrogen gas is introduced, the bias voltage is not turned on, the first and second sets of chromium rake arc sources are turned on, the arc current is 180A, the coil current is 350mA, the electron collector is 40A, the pressure inside the furnace is maintained at 2.65Pa, and the time is 9 hours.

[0024] Furthermore, in step 3, the coating process ends, and the furnace temperature of the multi-arc ion plating machine drops to 100°C before the product is removed from the furnace.

[0025] A CrN-coated pointed scraper ring, the scraper ring being processed by the above-mentioned coating process, comprising a substrate, the head of the substrate having a pure chromium layer, the surface of the pure chromium layer being plated with a CrN layer, the thickness of the pure chromium layer being 2 μm, the thickness of the CrN layer being 22-27 μm, and the hardness being 1270 HV.

[0026] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0027] (1) The scraper ring of the present invention is cleaned by I ET for 10-20 minutes, and the surface of the scraper ring is removed by argon atom bombardment;

[0028] (2) The scraper ring of the present invention is bombarded by three sets of 600V and 800V, and nitrogen atoms are used to strike the surface of the scraper ring to clean the surface again, further improving the cleanliness and laying the foundation for improving the bonding strength of the film layer.

[0029] (3) In this invention, the substrate hardness of the scraper ring is about 400-500 HV, and the hardness of CrN is about 1200-1600 HV. If CrN is directly coated on the substrate, the hardness range is large, which has a significant impact on the bonding strength and makes it easy for the coating to peel off. Pure chromium has a hardness of about 800-900 HV. Adding a pure chromium layer between the substrate and CrN plays a transition role, effectively improving the bonding strength and avoiding coating peeling.

[0030] (4) The present invention does not apply a bias voltage when plating CrN, which can control the hardness of CrN to the lower limit, about 1200-1300HV. The hardness is relatively low, and the brittleness is also less, which further reduces the risk of delamination.

[0031] (5) In this invention, the scraper ring is cooled to below 100°C before being taken out of the furnace, which reduces the temperature difference between the scraper ring and the ambient environment and avoids the scraper ring from bursting due to excessive cooling. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention;

[0033] In the figure: 1-substrate, 2-pure chromium layer, 3-CrN layer. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] In one embodiment of the present invention, a CrN coating tip scraper ring coating process is described, which utilizes multi-arc ion plating technology, using metallic Cr as the target material and nitrogen as the reactant gas. A negative bias voltage is applied to the substrate after surface cleaning, and a current is applied to the Cr target to deposit a CrN coating on the substrate surface. The process steps are as follows:

[0036] Step 1: Immerse the scraper ring in a water-based cleaning solution and ultrasonically clean for 5 minutes to remove oil stains;

[0037] Step 2: After two water washes, perform rust prevention and drying;

[0038] Step 3: After the scraper ring has cooled, immerse it in a hydrocarbon solution and rinse it again for 2 minutes;

[0039] Step 4: Dry the cleaned scraper ring by drying it with dryer or hot air.

[0040] Step 5: Clamp the scraper ring onto a special fixture and place it on the rotating frame of the multi-arc ion plating machine for CrN coating treatment. In this embodiment, the multi-arc ion plating machine used has a total of 15 arc sources. Sources 1#-12# are chromium target arc sources with a diameter of 155mm, and sources 13#-15# are titanium target arc sources with a diameter of 100mm. The multi-arc ion plating machine has an electron collector and coils. The multi-arc ion plating machine is divided into three groups of arc sources: the first group of chromium target arc sources (1#-6#), the second group of chromium target arc sources (7#-12#), and the third group of titanium target arc sources (13#-15#). The CrN coating treatment is as follows:

[0041] Vacuuming: Vacuuming is performed inside the multi-arc ion plating machine to achieve a vacuum level of 0.005 Pa.

[0042] Heating: Turn on the heater to raise the furnace temperature to 390℃, while simultaneously achieving a vacuum level of 0.007 Pa.

[0043] I ET cleaning: Introduce argon gas, set the bias voltage to 100V, frequency to 40Hz, and duty cycle to 70%. Activate titanium rakes #13-#15, with an arc current of 90A for each. Cleaning time is 15 minutes.

[0044] First bombardment: Nitrogen gas is introduced, bias voltage is set to 600V, frequency to 40Hz, duty cycle to 70%, chromium rakes #1-6 are turned on, arc current is 80A for each, bombardment time is 120 seconds, chromium rakes #1-6 are turned off, chromium rakes #7-12 are turned on, arc current is 80A for each, bombardment time is 120 seconds, chromium rakes #7-12 are turned off, bombardment 1 ends, stop for 120 seconds.

[0045] Second bombardment: Nitrogen gas is introduced, bias voltage is set to 800V, frequency to 40Hz, duty cycle to 70%, chromium rakes #1-6 are turned on, arc current is set to 80A, bombardment time is 90 seconds, chromium rakes #1-6 are turned off, chromium rakes #7-12 are turned on, arc current is set to 80A, bombardment time is 90 seconds, chromium rakes #7-12 are turned off, bombardment 2 ends, stop for 120 seconds.

[0046] Third bombardment: Nitrogen gas is introduced, bias voltage is set to 800V, frequency to 40Hz, duty cycle to 70%, chromium rakes #1-6 are turned on, arc current is set to 80A, bombardment time is 90 seconds, chromium rakes #1-6 are turned off, chromium rakes #7-12 are turned on, arc current is set to 80A, bombardment time is 90 seconds, chromium rakes #7-12 are turned off, bombardment 3 ends.

[0047] Pure chromium plating: Argon gas is introduced, bias voltage is turned on at 60V, frequency at 40HZ, duty cycle at 75%, chromium rakes 1#-12# are turned on, arc current is 180A, coil current is 350mA, electron collector current is 40A, furnace pressure is maintained at 2.65Pa, and time is 1 hour.

[0048] CrN plating: Nitrogen gas is introduced, no bias voltage is applied, chromium rakes #1-#12 are turned on, arc current is 180A, coil current is 350mA, electron collector current is 40A, furnace pressure is maintained at 2.65Pa, and time is 9 hours.

[0049] After the coating process is completed, the furnace temperature of the multi-arc ion plating machine drops to 100℃ before the product is taken out.

[0050] Please see Figure 1 In another embodiment of the present invention, a CrN-coated pointed scraper ring is provided. The scraper ring is processed by the above-mentioned coating process and includes a substrate 1. The head of the substrate 1 has a pure chromium layer 2. The surface of the pure chromium layer 2 is plated with a CrN layer 3. The thickness of the pure chromium layer 2 is 2 μm, the thickness of the CrN layer is 22-27 μm, and the hardness is 1270 HV.

[0051] No film detachment was observed on the scraper ring after baking. Ten scrapers were randomly selected and twisted 180 degrees without film detachment, indicating good adhesion. One scraper was taken from the top, middle, and bottom for testing: pure chromium layer thickness was 2µm, CrN layer thickness was 22-27µm, and hardness was 1270HV.

[0052] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A process for preparing a CrN coating with a pointed scraper ring, using a multi-arc ion plating machine, employing multi-arc ion plating technology, using metallic Cr as the target material, nitrogen as the reactant gas, applying a negative bias voltage to a substrate after surface cleaning, applying a current to the Cr target, and depositing a CrN coating on the substrate surface, characterized in that... The multi-arc ion plating machine is divided into three groups of arc sources: a first group of chromium target arc sources, a second group of chromium target arc sources, and a third group of titanium target arc sources. The process steps are as follows: Step 1: Clean and pre-treat the surface of the scraper ring; Step 2: Perform IET cleaning on the surface of the scraper ring, and apply a bias voltage of 100V, frequency of 40HZ, and duty cycle of 70% to the multi-arc ion plating machine; Step 3: The scraper ring performs three bombardments. First bombardment: Nitrogen gas is introduced into the furnace. The multi-arc ion plating machine applies a bias voltage of 600V, a frequency of 40HZ, and a duty cycle of 70%. The first set of chromium target arc sources is turned on, with an arc current of 80-120A and a bombardment time of 90-120 seconds. The first set of chromium target arc sources is turned off. The second set of chromium target arc sources is turned on, with an arc current of 80-120A and a bombardment time of 90-120 seconds. The second set of chromium target arc sources is turned off. The first bombardment ends, and there is a 120-second pause. Second bombardment: Nitrogen gas is introduced into the furnace again. The multi-arc ion plating machine is biased at 800V, frequency at 40Hz, and duty cycle at 70%. The first set of chromium target arc sources is turned on with an arc current of 80-120A and a bombardment time of 90-120 seconds. The first set of chromium target arc sources is turned off, and the second set of chromium target arc sources is turned on with an arc current of 80-120A and a bombardment time of 90 seconds. The second set of chromium target arc sources is turned off, and the second bombardment ends. The process is paused for 110-120 seconds. Third bombardment: Nitrogen gas is introduced into the furnace again. The multi-arc ion plating machine is biased at 800V, frequency at 40Hz, and duty cycle at 70%. The first set of chromium target arc sources is turned on with an arc current of 80-120A and a bombardment time of 90-120 seconds. The first set of chromium target arc sources is turned off, and the second set of chromium target arc sources is turned on with an arc current of 80-120A and a bombardment time of 90-120 seconds. The second set of chromium target arc sources is turned off, and the third bombardment ends. Step 4: Apply a chromium layer to the surface of the scraper ring using a multi-arc ion plating machine, and then perform CrN plating; Step 5: After the CrN coating is completed, lower the furnace temperature of the multi-arc ion plating machine and remove the scraper ring with the CrN coating. In step 2, the IET cleaning is further specified as follows: Argon gas is introduced into the furnace of the multi-arc ion plating machine, a bias voltage of 100V, a frequency of 40HZ, a duty cycle of 70% is applied, the third set of titanium target arc sources is turned on, the arc current is 80-100A, and the cleaning time is 10-20 minutes. In step 4, the specific process of plating a chromium layer on the surface of the scraper ring using a multi-arc ion plating machine is as follows: Argon gas is introduced, a bias voltage of 60V is applied, the frequency is 40HZ, the duty cycle is 75%, the first and second groups of chromium target arc sources are turned on, the arc current is 180A, the coil current is 350mA, the electron collector is 40A, the pressure inside the furnace is maintained at 2.65Pa, and the time is 1h. In step 4, the process of CrN coating on the surface of the scraper ring by the multi-arc ion plating machine is as follows: nitrogen gas is introduced, no bias voltage is turned on, the first set of chromium target arc sources and the second set of chromium target arc sources are turned on, the arc current is 180A, the coil current is 350mA, the current of the electron collector is 40A, the pressure inside the furnace is maintained at 2.65Pa, and the time is 9h.

2. The process for preparing a CrN-coated pointed scraper ring coating according to claim 1, characterized in that, Step 1, the pre-treatment for cleaning, includes the following steps: Step 11: The scraper ring is immersed in an alkaline solution for ultrasonic cleaning to remove oil stains; Step 12: Remove rust and dry after two water washes; Step 13: After the scraper ring has cooled, immerse it in a hydrocarbon solution for another cleaning; Step 14: Dry the cleaned scraper ring by drying it with dryer or hot air.

3. The process for preparing a CrN-coated pointed scraper ring coating according to claim 1, characterized in that, After cleaning and pretreatment of the scraper ring surface, the furnace of the multi-arc ion plating machine is evacuated, and water vapor in the furnace is removed at the same time, so that the vacuum degree in the furnace reaches below 0.005 Pa. After the vacuum degree in the furnace reaches below 0.005 Pa, heating is carried out to raise the furnace temperature to 380-400℃, while ensuring that the vacuum degree is below 0.007 Pa.

4. The process for preparing a CrN-coated pointed scraper ring coating according to claim 1, characterized in that, In step 5, the coating process is completed, and the furnace temperature of the multi-arc ion plating machine drops to 100°C before the product is removed from the furnace.

5. A CrN-coated pointed scraper ring, wherein the scraper ring is manufactured by the coating preparation process described in claim 1, characterized in that, It includes a substrate, the head of which has a pure chromium layer, the surface of which is plated with a CrN layer, the thickness of which is 2 μm, the thickness of which is 22-27 μm, and the hardness of which is 1270 HV.

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