JP5455149B2 - Iron-based thermal spray coating - Google Patents

Description

  The present invention provides an iron-based thermal spray coating capable of improving the wear resistance and scuff resistance of an alloy component by coating the surface of the component made of an aluminum alloy, and a vehicle equipped with such a thermal spray coating. It relates to parts.

In recent years, for the purpose of reducing the weight of vehicles, aluminum alloy cylinder blocks have been used for automobile internal combustion engines, and those with cast iron liners on the bore surface have become the mainstream. ing.
In this case, from the viewpoint of further weight reduction of engine parts, instead of cast iron liners, the development of cylinder blocks in which aluminum liners are cast or aluminum alloy monoblocks in which cast iron liners are completely abolished is being promoted. It has been.

However, aluminum liners and aluminum alloy monoblocks have problems with wear resistance and scuff resistance, and may be subjected to plating treatment such as nickel plating. Even in this case, wear resistance and scuff resistance Is not enough.
As countermeasures, measures are taken to improve wear resistance and scuff resistance by melting powder and wire with plasma flame to form droplets and spraying them on the inner surface of the cylinder bore to form a sprayed coating. It has been. That is, by spraying iron-based alloy powder onto the bore surface of the engine cylinder block, the wear resistance and scuff resistance of the piston ring and piston are improved (for example, see Patent Document 1).

JP 2000-212717 A

In the method described in Patent Document 1, the wear resistance and scuff resistance of the piston ring and the piston are improved by a sprayed coating formed by spraying an iron-based alloy powder.
However, in a cylinder block where a very high in-cylinder pressure is applied like a recent high-power engine, a high load is repeatedly applied to the sprayed coating due to a high combustion pressure, so cracks and peeling may occur inside the sprayed coating. I understand. When the peeling inside the thermal spray coating becomes large, the oil consumption deteriorates, and when the thermal spray coating reaches the complete peeling, it becomes a factor of scuffing with the piston ring and the piston.

  Also, compared to current cast iron liners, aluminum monoblock and nickel-plated products have problems with wear resistance and scuff resistance, so when using iron spraying, improve wear resistance and scuff resistance. Measures are needed.

  The present invention has been made in view of the above-mentioned problems in an iron-based thermal spray coating on an aluminum alloy, and the object thereof is to combine excellent wear resistance and scuff resistance, for example, a cylinder of a high-power engine. An object of the present invention is to provide an iron-based sprayed coating that exhibits sufficient durability (peeling resistance) to be applied to blocks.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on the material components of the iron-based thermal spray coating and the suitable hardness range of the coating, and as a result, sufficient durability even in a high combustion pressure load environment. Have found a component system of a thermal spray coating that exhibits high resistance (peeling resistance) and high scuff resistance, and has completed the present invention.

  That is, the present invention is based on the above knowledge, and the iron-based sprayed coating of the present invention is a sprayed coating for coating the surface of an aluminum alloy base material, and C is 0.3 to 0.00. 4% by mass, Si 0.2-0.5% by mass, Mn 0.3-1.5% by mass, Cr and / or Mo in total of 0.5% by mass or less, the balance being Fe and inevitable It is a characteristic impurity.

  A vehicle component of the present invention, or a component for an internal combustion engine such as a cylinder block, is provided with the iron-based thermal spray coating of the present invention. In particular, in a cylinder block for an internal combustion engine, the inner surface of the bore is provided. Is provided with an iron-based thermal spray coating.

  According to the present invention, since the component of the iron-based spray coating formed on the surface of the aluminum alloy base material is in the above range, it becomes a spray coating having excellent wear resistance and scuff resistance, for example, for a high-power engine. Even when applied to an aluminum alloy cylinder block, it exhibits sufficient durability and peel resistance.

It is a cross-sectional photograph which shows an example of the iron-type thermal spray coating of this invention. It is a schematic explanatory drawing which shows the peeling evaluation point of the thermal spray coating in an Example. It is a schematic explanatory drawing which shows the scuff evaluation point of the sprayed coating in an Example. It is a schematic explanatory drawing which shows the abrasion evaluation point of the sprayed coating in an Example.

  Hereinafter, the iron-based thermal spray coating of the present invention will be described more specifically and in detail along with its manufacturing method and the like, taking a cylinder block for an internal combustion engine as an example. In the present specification, “%” means mass percentage unless otherwise specified.

First, a thermal spraying method for obtaining the iron-based thermal spray coating of the present invention, that is, a heat source for melting a powdery, rod-like, or wire-like thermal spray material is not particularly limited and has been put into practical use so far. Various methods can be employed.
For example, flame spraying using the reaction heat of fuel gas and oxygen, explosive spraying using the explosive force of a mixed gas of oxygen and acetylene, laser spraying using a laser, fine particles of a material melted by the heat of an arc with high-speed gas For example, arc spraying that is sprayed and sprayed, plasma spraying in which a material melted by feeding into a plasma jet is accelerated by a plasma pressure, and laser-plasma composite spraying can be applied.

Next, in the manufacturing process, as an example of an aluminum alloy base material, after casting a cylinder block, in order to improve the adhesion of the sprayed coating, the inner surface of the cylinder bore is grounded, and the cylinder after the grounding is processed. A ferrous metal material is sprayed as droplets on the inner surface of the bore to form a sprayed coating.
Here, when iron-based metallic material is used as droplets, as described in Patent Document 1, it is common to use iron-based alloy powder, but it is advantageous in terms of cost. In the present invention, it is preferable to use an iron-based alloy wire.

  The spray coating can be formed by spraying a spray wire or a spray powder melted by a combustion flame while moving the spray gun inserted into a cylindrical cylinder bore from one end to the other. A spray coating can be formed by spraying from the tip of the gun to the inner surface.

FIG. 1 shows a cross-sectional photograph of the sprayed coating thus obtained. As shown in the figure, the iron-based sprayed coating of the present invention contains pores and iron oxide in the coating. .
The pores function as an oil reservoir and have the effect of improving the scuff resistance of the thermal spray coating. However, if the amount is too large, sufficient durability (peeling resistance) may not be obtained. The area ratio is desirably 2.1% or less.
On the other hand, iron oxide has a function as a solid lubricant, but when the amount of iron oxide contained in the sprayed coating is small, scuff resistance cannot be obtained, and conversely, when it is too much, sufficient durability is obtained. Since the tendency to not obtain (peeling resistance) is shown, the volume ratio of the porosity is preferably in the range of 5 to 35%.

  Hereinafter, the reason for limiting the range of the component composition in the iron-based sprayed coating of the present invention will be described.

C: 0.3 to 0.4%
First, as for carbon (C), when the carbon content contained in the iron-based sprayed coating of the present invention is low, sufficient durability (peeling resistance) cannot be ensured. As a result, the mating sliding parts (piston and piston ring in the case of a cylinder block) will be significantly worn.
Therefore, in this invention, it is necessary to make carbon content into the range of 0.3-0.4% by mass ratio.

Si: 0.2 to 0.5%
Mn: 0.3 to 1.5%
Next, about silicon (Si) and manganese (Mn), when these amounts contained in the sprayed coating of the present invention are low, sufficient durability (peeling resistance) and wear resistance cannot be ensured. On the other hand, when these contents are high, the opponent's aggression becomes higher as the hardness is increased, and the counterpart sliding part is significantly worn. Further, when the amount of Mn is high, the generation of iron oxide is hindered due to deoxidation drop, and the scuff resistance is deteriorated.
Therefore, in the iron-based sprayed coating of the present invention, it is necessary to limit the amounts of Si and Mn contained in the ranges of 0.2 to 0.5% and 0.3 to 1.5%, respectively. .

Cr + Mo: 0.5% or less Both chromium (Cr) and molybdenum (Mo) are added in order to improve durability (peeling resistance). When the content of is too high, an oxide is formed, so that the production of iron oxide is hindered and the scuff resistance is remarkably deteriorated.
Therefore, in the present invention, it is necessary to limit the total amount of Cr and Mo contained in the iron-based sprayed coating to 0.5% or less. If these contents are too low, it is difficult to ensure sufficient durability (peeling resistance), so the total content is preferably at least about 0.02%. .

In the iron-based thermal spray coating of the present invention, by setting the component composition within the above range, a thermal spray coating having abrasion resistance, scuff resistance, and peeling resistance and excellent in durability can be obtained.
In general, it is known that the coating component by thermal spraying is almost dependent on the chemical composition of the thermal spray material used, but since there is a concern about decarburization of the coating material, the carbon content of the wire material used as a raw material is slightly increased. Sometimes set. The form of the thermal spray material is not particularly limited, such as powder or rod, but it is desirable to use a wire-like material as described above.

Regarding the hardness of the thermal spray coating formed on the inner surface of the bore by thermal spraying, if the hardness of the thermal spray coating is low, there is a possibility that significant bore wear may occur due to the mating piston ring. On the other hand, when the thermal spray coating hardness is high, the opponent's aggression becomes high, and the piston or piston ring that is the counterpart sliding part may be significantly worn.
Therefore, in the present invention, it is preferable that the hardness of the iron-based sprayed coating (Vickers hardness) is in the range of HV 250 to 500.

  In addition, as thickness of the iron-type thermal spray coating of this invention, although it is also necessary to prepare according to the kind of aluminum alloy parts to apply, it should be in the range of several micrometers-several hundred micrometers generally. desirable.

  The iron-based thermal spray coating of the present invention can be applied to aluminum alloy internal combustion engine parts such as a cylinder block, a cylinder head, and a piston. More specifically, the iron-based thermal spray coating of the present invention can be applied to the bore inner surface of the cylinder block, etc., improving the wear resistance and scuffing resistance of the coated surface and improving the durability of the part. be able to.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, it cannot be overemphasized that this invention is not limited at all by such an Example.

[Formation of Thermal Sprayed Coating (Examples 1 to 10, Comparative Examples 1 to 14)]
Using an aluminum alloy plate as a base material, an iron-based thermal spray coating is performed by plasma spraying using an iron-based wire material (diameter: 1.4 to 1.8 mm) having a copper plating on the surface and having different components. Was formed to a thickness of about 300 μm, and each size test specimen was cut out and subjected to the following evaluation test.
The basic conditions for plasma spraying were plasma current: 90 A, plasma voltage: 100 V, gas flow rate (Ar + H ₂ ): 100 L / min, and torch speed: 120 cm / min.

  Table 1 shows the measurement results of the components and hardness of these iron-based thermal spray coatings. In Table 1, “others” means inevitable components, and in addition to P and S, Cu derived from copper plating applied to the wire surface is also included. Moreover, it cannot be overemphasized that the remainder other than a numerical value described is iron (Fe).

[Performance evaluation]
The following performance evaluation was performed using each evaluation test piece cut out from the aluminum alloy sheet material of each example to which the iron-based thermal spray coating was applied.

(1) Peeling evaluation method of sprayed coating As a peeling evaluation of sprayed coating, an evaluation test piece of the following size obtained in each example was subjected to a test using a blast testing machine as shown in FIG. The weight of the test piece was measured, and the weight loss (sprayed amount of the sprayed coating) was used as an index of peel resistance. Table 2 shows the test results obtained under the following test conditions.
・ Outline of testing machine: Fig. 2
・ Test specimen shape: 50 × 50 mm (5 mm thick)
・ Blasting material: Ablacks # 54 (alumina particles)
・ Irradiation amount: 50g / time, 5 times in total (250g)
・ Measuring method: Alumina particles are irradiated onto the sprayed surface, and the weight difference between the sprayed specimens before and after the test is measured.

(2) Scuff evaluation test method with piston ring As a scuff evaluation of the thermal spray coating, by pressing a cylindrical test piece as the mating sliding material against the evaluation test piece of the following size obtained in each example, A rotational sliding test as shown was performed, and the scuffing resistance of each test piece was measured. The test results obtained under the following test conditions are also shown in Table 2.
・ Outline of testing machine: Fig. 3
・ Test specimen shape: 50 × 50 mm (5 mm thick)
・ Measuring method: Increase the load by 10kgf, and make the point of sudden increase in friction force a ring scuff load ・ Sliding speed: 0.2m / s
・ Temperature: 25 ℃
・ Lubricant: 5W30SL (only initial application)
・ Sliding material (equivalent to piston ring): Carbon steel is used as the base material and the sliding surface is covered with CrN

(3) Wear evaluation test method with piston ring As a friction evaluation of the thermal spray coating, a bar-shaped test piece having a D-shaped cross section was pressed against the evaluation test piece of the following size obtained in each example, A reciprocating frictional wear test as shown in Fig. 4 was carried out, and the wear amount of both was measured (the amount of wear thinning was measured using a shape measuring instrument). The test results obtained under the following test conditions are also shown in Table 2.
・ Outline of testing machine: Fig. 4
-Test piece shape: 40 x 70 mm (wall thickness 5 mm)
・ Sliding speed: 0.5m / s
・ Temperature: 25 ℃
・ Pressing load: 10kgf
・ Test time: 1 hour ・ Lubricant: 5W30SL
・ Sliding material (equivalent to piston ring): Carbon steel is used as the base material and the sliding surface is covered with CrN

In Table 2, the peel test results indicate relative values where the amount of decrease in the test piece weight of Example 1 is “1”, and the smaller the value, the better the peel resistance of the thermal spray coating. Show.
Further, the scuff load in the scuff evaluation test result means a pressing load where the scuff is generated, and the larger the value, the better the thermal spray coating is. Further, the results of the wear test are expressed as relative values with the wear amount in Example 1 being “1”.
As for “Sprayed coating wear amount”, the smaller the value, the smaller the wear of the sprayed coating itself. As for the “Countermaterial wear amount”, the smaller the value, the smaller the wear amount of the counterpart material, It shows that there is no sex problem.

  As is apparent from the results of Tables 1 and 2, the iron-based thermal spray coatings according to Examples 1 to 10 of the present invention have extremely good performance in all test items compared to the thermal spray coatings according to Comparative Examples 1 to 14. In particular, a remarkable improvement width in peeling resistance and scuff resistance was confirmed.

Among the above Comparative Examples 1 to 14, the thermal spray coatings of Comparative Examples 1, 2 and 13 with low carbon and low coating hardness have good mating material wear (parity attack), but their own wear resistance. It turns out that the nature is inferior. A similar tendency is observed in the thermal spray coatings of Comparative Example 5 having a low Si content and Comparative Example 7 having a low Mn content.
On the other hand, in the thermal spray coatings of Comparative Examples 4 and 14 having high carbon and high coating hardness, it was confirmed that, on the contrary, the aggressiveness against the counterpart material was extremely high.

Claims (6)

In the iron-based thermal spray coating that covers the surface of the aluminum alloy base material,
In a mass ratio, 0.3 to 0.4% of C, 0.2 to 0.5% of Si, 0.3 to 1.5% of Mn, and Cr and / or Mo in total 0.5 An iron-based sprayed coating characterized by containing not more than% and the balance being Fe and inevitable impurities.   The iron-based thermal spray coating according to claim 1, wherein the hardness is HV 250 to 500 in terms of Vickers hardness.   A vehicle component comprising the iron-based thermal spray coating according to claim 1.   An internal combustion engine component comprising the iron-based thermal spray coating according to claim 1.   A cylinder block for an internal combustion engine, comprising the iron-based thermal spray coating according to claim 1.   6. The cylinder block for an internal combustion engine according to claim 5, wherein the iron-based sprayed coating is provided on an inner surface of the bore.

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