JP2005171274A - Method for forming sprayed coating and sliding member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a thermal spray coating excellent in scuff resistance and wear resistance while ensuring adhesion between the thermal spray coating and a sprayed body.
In forming a thermal spray coating by spraying a thermal spray gun melted by a plasma flame from a nozzle tip while moving a thermal spray gun from one end side to the other end side with respect to a bore inner surface of a cylinder bore, The supply amount of the auxiliary gas supplied to the spray gun is made smaller than the supply amount (reduction level Q2) at the second plasma spraying with respect to the supply amount at the first plasma spraying (initial setting flow rate Q1). If the auxiliary gas supply amount is reduced, many fine pores can be formed in the sprayed coating, and lubricant can be retained in the pores, greatly improving scuff resistance and wear resistance. Can be improved.
[Selection] Figure 4

Description

  The present invention relates to a method for forming a thermal spray coating on a thermal sprayed body by plasma spraying and a sliding member formed by the method.

  For example, the thermal spray coating formed on the base material (matrix) is irradiated with a laser in a pattern such as a dot or a line to partially heat and cause a structural change to partially modify the thermal spray coating, There is a method of forming a sliding surface with excellent seizure resistance by recessing the laser irradiated part or laser non-irradiated part mainly due to selective wear during finishing or sliding and using the recess as an oil reservoir. It has been proposed (see, for example, Patent Document 1).

According to the method described in Patent Document 1, since the lubricating oil accumulates in the recess, the recess becomes an oil reservoir, and the oil retention is improved. As a result, the seizure resistance of the sprayed coating formed on the substrate can be improved.
JP 2001-279421 A (2nd and 3rd pages, FIGS. 1 to 3)

  However, in the method described in Patent Document 1, since the wear form is affected by the engine operating state, the dent on the sliding surface is not stabilized, leading to quality degradation. Further, in the method described in Patent Document 1, since there is laser processing in addition to the normal finishing process, the process becomes complicated and the cost increases. Furthermore, in the method described in Patent Document 1, when laser heat treatment is performed on a thermal spray coating of an Fe (iron) -based thermal spray material, the hardness in the boundary region with or without laser irradiation tends to become harder. As a result, a protrusion shape remains in the surface property, and this leads to wear of the piston and piston ring.

  Accordingly, the present invention provides a method for forming a thermal spray coating and a sliding member that are excellent in scuff resistance (strength against scratches) and wear resistance while ensuring the adhesion between the thermal spray coating and the sprayed body. For the purpose.

  The method for forming a thermal spray coating of the present invention involves spraying a thermal spray powder melted by a plasma flame from the nozzle tip while moving the thermal spray gun from one end side to the other end side with respect to the thermal spray body. Form a film. In the method of the present invention, when the spray coating is formed, the supply amount of the auxiliary gas supplied to the spray gun is increased or decreased according to the spray position of the sprayed object.

  According to the present invention, when the spray coating is formed, the amount of auxiliary gas supplied to the spray gun is varied according to the spraying position of the sprayed object. The porosity of the thermal spray coating is large (many fine pores) in a portion where the porosity of the sprayed gas is small (formation with few fine pores) and the supply amount of the auxiliary gas is small.

  Therefore, if the sprayed coating formed by this method is formed on the inner surface of the bore of the cylinder bore, the minute pores function as an oil reservoir for collecting oil. The lubricating oil consumption and the frictional force can be reduced while ensuring sufficient.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

[Schematic configuration and operation of plasma spraying apparatus]
First, before describing a method for forming a sprayed coating to which the present invention is applied, a plasma spraying apparatus used in this method will be briefly described.

  FIG. 1 is a schematic configuration diagram of a plasma spraying apparatus, FIG. 2 is a principle diagram of plasma spraying, and FIG. As shown in FIG. 1, the plasma spraying apparatus includes a spraying gun 1, a vertical sliding device 2 that moves the spraying gun 1 up and down, a rotating device 3 that rotates the spraying gun 1, a robot 4, and a plasma flame. And an auxiliary gas supply device 5 for generation.

  The thermal spray gun 1 has a nozzle 6 for ejecting thermal spray powder melted by a plasma flame. As shown in FIG. 2, the thermal spray gun 1 supplies argon gas (Ar gas) or hydrogen gas (H 2 gas) into the nozzle 6 as an auxiliary gas, and the nozzle 6 serves as an anode, and is provided in the nozzle 6. A direct current is applied from a direct current power source 8 to the cathode 7 to generate a direct current arc 9, and a plasma flame is generated by the auxiliary gas. Then, the thermal spray powder 10 is supplied in front of the DC arc 9, the thermal spray powder 10 is melted, and the molten thermal spray powder 10 is ejected from the nozzle tip.

  A cooling water introduction hole 11 for cooling the nozzle tip is formed near the tip of the nozzle 6. By introducing the cooling water into the cooling water introduction hole 11, the nozzle tip is prevented from being heated by the plasma flame.

  The vertical sliding device 2 makes the above-described thermal spray gun 1 movable in the vertical direction indicated by an arrow X in a cylinder bore 12 of a cylinder block made of an aluminum alloy in, for example, an automotive engine that is a sprayed body. The rotating device 3 has an arrow on the thermal spray gun 1 so that the molten thermal spray powder 10 ejected from the nozzle tip of the thermal spray gun 1 can be sprayed over the entire circumference of the bore inner surface 12a which is the sprayed surface of the cylinder bore 12. It can be rotated in the horizontal direction indicated by. The robot 4 controls the operations of the thermal spray gun 1, the vertical sliding device 2, and the rotating device 3.

  For example, the auxiliary gas supply device 5 serves to supply argon gas or hydrogen gas as auxiliary gas into the nozzle 6. The auxiliary gas is supplied from the auxiliary gas supply device 5 to the nozzle 6 via the auxiliary gas supply pipe 13. Further, the supply amount of the auxiliary gas is appropriately adjusted as described later according to the number of times of spraying (number of strokes) by the spraying gun 1 and the spraying position (stroke position of the spraying gun 1) and supplied to the nozzle 6. .

  In the plasma spraying apparatus configured as described above, the spraying gun 1 is inserted into the cylinder bore 12, and the spraying gun 1 is moved up and down while being rotated by the rotating device 3 and the vertical sliding device 2. The sprayed powder 10 melted from the tip is sprayed onto the bore inner surface 12a. Thereby, the thermal spray coating 14 is formed on the bore inner surface 12a.

  In addition, the adhesive force of the thermal spray coating 14 can be enhanced by blasting the portion where the thermal spray coating 14 is formed before the thermal spraying. By forming the thermal spray coating 14 in this way, the thermal spray coating 14 can be firmly adhered to the bore inner surface 12a, and a thermal spray coating 14 having stable coating properties can be obtained.

  After forming the sprayed coating 14 using the plasma spraying apparatus described above, the sprayed coating 14 is finished by honing. Fine pores peculiar to the thermal spray coating are formed on the surface of the thermal spray coating 14 after the finishing process, and the generation rate of the pores varies depending on argon gas or hydrogen gas which is an auxiliary gas supplied to the nozzle 6. . For example, as shown in FIG. 3, the pore generation rate tends to increase when the hydrogen gas supply amount is small, and the pore generation rate tends to decrease when the hydrogen gas supply amount is large. This is because the energy of the plasma flame changes depending on the supply amount of the auxiliary gas and affects the laminated state of the coating particles.

  The porosity generation rate can also be represented by Rvk, which is an oil reservoir index of the surface roughness of the thermal spray coating 14.

  In this way, by controlling the supply rate of the auxiliary gas supplied to the nozzle 6 to control the porosity generation rate or Rvk formed in the sprayed coating 14, the scuffing resistance and wear resistance that are required functions of the sprayed coating 14 are controlled. Property, oil consumption and friction reduction can be optimized, and a desired film can be obtained.

[Example]
Next, an example of a thermal spray coating forming method for forming the thermal spray coating 14 that can satisfy scuffing resistance, wear resistance, and the like by controlling the amount of auxiliary gas supplied to the nozzle 6 will be described.

  FIG. 4 is a diagram showing an example of increasing or decreasing the hydrogen gas supply amount according to the spraying position of the cylinder bore, FIG. 5 is a flowchart showing a method of forming a sprayed coating of the method of the present invention, and FIG. 6 is an enlarged view of the sprayed coating after plasma spraying FIG. 7 is an enlarged cross-sectional view of the main part showing the thermal spray coating after the honing finish.

  In this embodiment, plasma spraying is performed in two stages, ie, an initial spraying stage (first spraying) L1 and a late spraying stage (second spraying) L2. That is, plasma spraying is performed in two steps. The thermal spraying initial stage L1 is indicated by a solid line in FIG. 4, and the thermal spraying late stage L2 is indicated by a one-dot chain line in FIG.

  In the initial stage of thermal spraying L1, in order to firmly adhere the thermal spray coating 14 to the bore inner surface 12a from the bottom dead center (BDC) to the top dead center (TDC) of the bore inner surface 12a, the initial hydrogen gas supply amount is set. Set flow rate Q1. In the later stage L2 of thermal spraying, the hydrogen gas supply amount is set to the initial flow rate Q1 from the bottom dead center to the position of the bore stroke SS1 in the vicinity of the top dead center, and the scuff resistance of the thermal spray coating 14 from the bore stroke SS1 to the top dead center. In order to optimize the wear resistance, oil consumption, and friction reduction, the hydrogen gas supply amount is set to a reduction level Q2.

  Specific values of the initial setting flow rate Q1 and the reduction level Q2 defined here are as shown in Table 1, for example. In the vicinity of the top dead center, the hydrogen gas supply rate is 1 to 3 (liters / minute), and the porosity generation rate (the ratio of the pores in the sprayed coating surface) is 5 to 15%. In the portion other than the top dead center, the hydrogen gas supply rate is 3 to 6 (liters / minute), and the porosity generation rate on the surface after the predetermined honing finish after the thermal spray coating is formed is 3 to 6%. In the vicinity of the top dead center, the porosity generation rate is increased in order to suppress bore wear due to the piston ring. That is, if the lubricating oil is accumulated in a large number of minute pores to improve the oil retaining property, the seizure resistance of the thermal spray coating 14 can be greatly improved.

Here, the highest position where the piston, which is slidable up and down in the cylinder bore 12, rises is defined as the top dead center, and the lowest position where the piston descends is defined as the bottom dead center.

  In order to form the sprayed coating 14 on the bore inner surface 12a of the cylinder bore 12, as shown in the flowchart of FIG. 5, first, in the process of step S1, the auxiliary gas supply amount is set to the initial setting flow rate Q1 (the auxiliary gas supply amount initial setting). ). Next, in the process of step S2, it is determined whether or not the number of spray strokes (the number of plasma sprays) is two or more. If the number of spray strokes is the first, spraying is performed with the auxiliary gas supply amount set to the initial flow rate Q1. At this time, thermal spraying is performed until one stroke for moving the thermal spray gun 1 from the bottom dead center to the top dead center is completed.

  When the thermal spray initial stage L1 is completed, a first thermal spray coating 14a having a film thickness t1 is formed on the bore inner surface 12a of the cylinder bore 12 as shown in FIG. Since the first sprayed coating 14a is supplied with hydrogen gas as the initial set flow rate Q1, it is firmly adhered to the bore inner surface 12a.

  In the process of step S6, it is determined whether or not the thermal spray gun 1 has completed one stroke. If one stroke has been completed, the process proceeds to step S7. If not, the process proceeds to step S3. Return to processing. In the process of step S7, it is determined whether or not the plasma spraying is finished. If the plasma spraying is finished, the flowchart is finished. If the plasma spraying is not finished, the flowchart is returned to the process of step S2.

  If the plasma spraying is the second time in the process of step S2, it is determined in step S3 where the nozzle 6 is located on the spraying position of the bore inner surface 12a (stroke position determination). If the nozzle 6 is in the bore stroke SS1 position (position near the top dead center), the auxiliary gas supply amount is adjusted in the process of step S4, and the auxiliary gas supply amount is set to the reduction level Q2. Then, plasma spraying is performed with the auxiliary gas supply amount set to the reduction level Q2.

  When the late spraying stage L2 is completed, the second thermal spray coatings 14b and 14c are formed on the first thermal spray coating 14a as shown in FIG. The In the late spraying stage L2, since the hydrogen gas supply amount is switched between the initial setting flow rate Q1 and the reduction level Q2 at the bore stroke position SS1, the properties of the thermal spray coatings 14b and 14c are the top dead center side E1 of the bore stroke range. Different properties are formed on the bottom dead center side E2.

  Next, after the plasma spraying is finished, the surface of the second sprayed coating 14 is honed. Then, as shown in FIG. 7, the thickness of the thermal spray coating 14 as a whole is reduced to t3 'and the thickness of the second thermal spray coatings 14b and 14c is reduced to t2' due to the finishing allowance. Many pores 15 are formed on the surface of the second thermal spray coating 14c on the top dead center side E1, and the pores 15 are formed on the surface of the second thermal spray coating 14b on the bottom dead center side E2 with the bore stroke position SS1 as a boundary. Few.

  As described above, since a large number of minute pores 15 are formed on the surface of the second thermal spray coating 14c on the top dead center side E1, the lubricating oil is accumulated in the pores 15 and the oil retaining property is improved. Scuff resistance and scuff resistance can be ensured. Further, since there are few pores 15 on the surface of the second thermal spray coating 14b on the bottom dead center side E2, oil consumption can be reduced and friction can be improved.

  As described above, if the plasma spraying is performed by adjusting the auxiliary gas supply amount according to the number of strokes and the stroke position, the adhesion with the bore inner surface 12a is secured, and the scuff resistance, wear resistance, and oil consumption are secured. In addition, it is possible to easily form the thermal spray coating 14 that optimizes friction reduction.

  In addition, it is possible to control the auxiliary gas supply amount in one plasma spraying device without switching the spraying powder in the middle of plasma spraying or performing plasma spraying for each type of sprayed powder. Therefore, it is possible to form an optimal sliding surface texture corresponding to the functional requirements.

[Other Examples]
Although specific embodiments to which the present invention is applied have been described above, the present invention can be variously modified without being limited to the above-described embodiments. For example, as shown in FIG. 8, in the initial stage of spraying L1, plasma spraying is performed from the bottom dead center to the top dead center with an auxiliary gas supply amount of an initial set flow rate Q1, and the late stage of spraying L2 is also started from the bottom dead center. Plasma spraying is performed with the auxiliary gas supply amount at the reduction level Q2 over the top dead center.

  Thus, by making the auxiliary gas supply amount at the time of the first movement of the spray gun 1 different from the auxiliary gas supply amount at the time of the second movement, all of the range from the bottom dead center side E2 to the top dead center side E1 can be obtained. Many fine pores 15 are formed on the surface of the second sprayed coating 14c. Therefore, in this embodiment, since the entire sprayed coating 14 formed on the bore inner surface 12a exhibits oil retention, the scuff resistance and wear resistance are further improved.

  In addition, as shown in FIG. 9, in the initial stage of spraying L1, plasma spraying is performed with the auxiliary gas supply amount of the initial set flow rate Q1 from the bottom dead center to the top dead center, and in the late stage of spraying L2, the vicinity of the center of the bore stroke is performed. Plasma spraying is performed from SS2 to SS3 with the hydrogen gas supply amount being reduced level Q2.

  Thus, the auxiliary gas supply amount in the bore inner surface 12a in the vicinity of the center of the bore stroke is made smaller than the auxiliary gas supply amount in the portion other than the vicinity of the center of the bore stroke. The adhesion is improved in the second sprayed coating 14b on the dead side E1, and the oil retaining property is improved in the vicinity of the center of the bore stroke. Therefore, if the sprayed coating 14 is formed in this way, the reliability can be improved even under conditions of a heavy engine load.

  In the above-described embodiment, the present invention is applied to the cylinder bore of the engine block as the sliding member. However, the present invention is not limited to this.

It is a schematic block diagram of a plasma spraying apparatus. It is a principle diagram of plasma spraying. It is a characteristic view which shows the relationship between hydrogen gas supply amount, a porosity generation rate, or surface roughness. It is a figure which shows an example which increases / decreases the hydrogen gas supply amount according to the spraying position of a cylinder bore. It is a flowchart which shows the formation method of the thermal spray coating of this invention method. It is a principal part expanded sectional view which expands and shows the sprayed coating after plasma spraying. It is a principal part expanded sectional view which expands and shows the sprayed coating after a honing process finish. It is a figure which shows the other Example and shows the example which increases / decreases the hydrogen gas supply amount according to the spraying position of a cylinder bore. Furthermore, it shows another embodiment, and is a diagram showing an example in which the hydrogen gas supply amount is increased or decreased according to the spraying position of the cylinder bore.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Thermal spray gun 2 ... Vertical sliding device 3 ... Rotating device 5 ... Auxiliary gas supply device 10 ... Thermal spray powder 12 ... Cylinder bore 12a ... Bore inner surface 14 ... Thermal spray coating 14a ... First thermal spray coating 14b, 14c ... Second thermal spray Coating 15: Pore L1 ... Initial stage of thermal spraying L2 ... Late stage of thermal spraying Q1 ... Initial set flow rate Q2 ... Reduction level

Claims (10)

When spraying the thermal spray powder melted by the plasma flame from the tip of the nozzle while moving the thermal spray gun from one end side to the other end side with respect to the thermal spray body, to form the thermal spray coating,
A method for forming a thermal spray coating, characterized in that a supply amount of auxiliary gas supplied to the thermal spray gun is varied according to a thermal spray position of the thermal spray body. When spraying the thermal spray powder melted by the plasma flame from the tip of the nozzle while moving the thermal spray gun from one end side to the other end side with respect to the thermal spray body, to form the thermal spray coating,
A method for forming a thermal spray coating, characterized in that an auxiliary gas supply amount supplied to the thermal spray gun during the first movement of the thermal spray gun is different from an auxiliary gas supply amount during the second and subsequent movements. A method for forming a thermal spray coating according to claim 1 or claim 2,
A method for forming a sprayed coating, wherein the sprayed body is a cylinder bore of an engine block. A method for forming a thermal spray coating according to claim 3,
A method for forming a thermal spray coating, characterized in that an auxiliary gas supply amount in a portion near a top dead center in an inner surface of the bore of the cylinder bore is less than an auxiliary gas supply amount in a portion other than a portion near the top dead center. A method for forming a thermal spray coating according to claim 3,
A method for forming a thermal spray coating, characterized in that an auxiliary gas supply amount at a portion near the center of the bore stroke on the inner surface of the bore of the cylinder bore is less than an auxiliary gas supply amount at a portion other than a portion near the center of the bore stroke. A method for forming a thermal spray coating according to claim 3,
A method for forming a thermal spray coating, characterized in that an auxiliary gas supply amount during the second and subsequent movements is less than an auxiliary gas supply amount supplied to the thermal spray gun during the first movement of the thermal spray gun. In a sliding member formed by forming a sprayed coating on the surface to be sprayed by plasma spraying,
The thermal spray coating has a portion with a high porosity and a portion with a low porosity. The sliding member according to claim 7,
The spray member is a bore inner surface of a cylinder bore in an engine block. The sliding member according to claim 8, wherein
A sliding member characterized in that the porosity of the thermal spray coating near the top dead center in the inner surface of the bore is larger than the porosity of the thermal spray coating other than the vicinity of the top dead center. The sliding member according to claim 8, wherein
A sliding member characterized in that the porosity of the sprayed coating near the center of the bore stroke in the inner surface of the bore is made larger than the porosity of the sprayed coating other than near the center of the bore stroke.

Images