JP4984214B2 - Iron-based sprayed thin film for cylinder block and cylinder block - Google Patents

Description

  The present invention relates to an iron-based sprayed thin film for a cylinder block and a cylinder block, and more particularly, to an iron-based sprayed thin film for a cylinder block excellent in peeling resistance under a high surface pressure and a cylinder block including the same.

  In conventional automotive engine blocks, cast iron liners were cast into aluminum alloy cylinder blocks, but from the standpoint of reducing engine parts, cast iron liners were not cast. A certain aluminum alloy monoblock is being developed. It is known that such an aluminum alloy monoblock has problems in wear resistance and scuff resistance.

Therefore, the wear resistance and scuff resistance of the piston ring and piston are improved by spraying iron alloy powder on the cylinder sliding surface of the engine block to form a sprayed coating (see Patent Document 1). .)
JP 2000-212717 A

However, even with the thermal spray coating described in Patent Document 1, in a cylinder block where a very high in-cylinder pressure is applied as in recent high-power engines, a high load is repeatedly applied to the thermal spray coating due to the high combustion pressure. Therefore, there is a problem that cracks and peeling occur inside the sprayed coating.
Further, when the peeling inside the sprayed coating is increased, the oil consumption is deteriorated, and when the sprayed coating is completely peeled off, it causes scuffing.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide an iron-based sprayed thin film for a cylinder block excellent in peeling resistance under a high surface pressure and the same. It is to provide a cylinder block.

  As a result of intensive investigations to achieve the above object, the present inventors have formed a laminated structure in which a plurality of iron spray particles having a predetermined particle diameter are layered on the cylinder bore inner surface of the cylinder block base material. The inventors have found that the above object can be achieved by forming an iron-based sprayed thin film for a cylinder block and have completed the present invention.

That is, the iron block thermal spray film for cylinder block of the present invention is formed on the inner surface of the cylinder bore of the cylinder block substrate, and has a laminated structure in which a plurality of iron spray particles are stacked in layers. It is a thin film, contains pores, has a porosity of 2.0% or less (area ratio in the sprayed section), contains iron oxide, and its content is 10-35% (area ratio in the sprayed section). The film thickness is 100 to 380 μm, and the relatively thin film regions A and the relatively thick film regions B are alternately arranged in the axial direction of the cylinder bore, and the film thickness of the region A is The ratio (B / A) of the film thickness of the region B to 1.3 is 7.5 to 7.5, the hardness is HV300 to 500, and the average roughness Ra of the surface corresponding to the cylinder bore inner surface is 0.4 μm or less. Yes, cylinder bore The oil retention depth Rvk in the surface roughness curve corresponding to the inner surface is 0.2 to 2.0 μm, and the iron spray particles have a particle diameter of 30 μm in the film thickness direction of the iron block sprayed thin film for cylinder block. The particle diameter in the axial direction of the cylinder bore is 30 to 300 μm.

  A cylinder block according to the present invention includes the iron-based sprayed thin film for a cylinder block according to the present invention.

  According to the present invention, an iron-based sprayed thin film for a cylinder block having a laminated structure in which a plurality of iron-based sprayed particles having a predetermined particle diameter are stacked in layers is formed on the cylinder bore inner surface of a cylinder block substrate. Therefore, it is possible to provide an iron-based thermal sprayed thin film for a cylinder block excellent in peel resistance under a high surface pressure and a cylinder block including the same.

Hereinafter, the iron-based sprayed thin film for cylinder blocks of the present invention will be described in detail. In the present specification and claims, “%” for concentration, content, etc. represents mass percentage unless otherwise specified.
As described above, the iron-based sprayed thin film for a cylinder block of the present invention is formed on the cylinder bore inner surface of the cylinder block base material and has a laminated structure in which a plurality of iron-based sprayed particles are stacked in layers.
Such iron-based spray particles have a particle diameter in the film thickness direction of the iron-based sprayed thin film for cylinder block of 30 μm or less and the axial direction of the cylinder bore, in other words, the reciprocating direction of the piston sliding with the cylinder bore surface. The particle diameter is 30 to 300 μm.
By adopting such a configuration, an iron-based thermal sprayed thin film for cylinder blocks having excellent peeling resistance (durability) can be obtained, and the cylinder block having the same has excellent peeling resistance (durability). Become.

First, the iron-based sprayed thin film for a cylinder block of the present invention is formed by, for example, a conventionally known thermal spraying method using, for example, a ferrous metal material as droplets on the inner surface of a cylinder bore of a cylinder block base material produced by casting. A thermal spray coating having a laminated structure formed by laminating a plurality of iron-based thermal spray particles in layers.
As an example of a method for forming such a thermal spray coating, the thermal spray gun inserted into the center of the cylindrical cylinder bore is moved from one end side to the other end side, and melted by a combustion flame from the tip of the thermal spray gun. Although the formation method of spraying the spray droplets of the sprayed powder on the inner surface of the cylinder bore as a spraying frame can be mentioned, it is not limited to this.
Moreover, the component of the iron-based metal material is not particularly limited. For example, an iron-based alloy material obtained by adding an alloy element such as carbon to iron can be used. And it is not specifically limited as a material shape before making these into a droplet, Although an iron-type alloy powder may be used, it is desirable to use an iron-type alloy wire.
Further, at this time, in order to improve the adhesion of the sprayed coating, a conventionally known undercoating that forms an uneven shape on the inner surface of the cylinder bore of the cylinder block substrate may be performed in advance.
Furthermore, honing may be applied to the surface after the formation of the sprayed coating.

  Further, the iron-based sprayed thin film for cylinder block of the present invention requires that the particle size in the film thickness direction of the iron-based sprayed thin film for cylinder block be 30 μm or less in the iron-based sprayed particles constituting the cylinder block. The particle diameter in the axial direction of the cylinder bore, that is, the piston sliding direction, is preferably 30 to 300 μm.

Here, the structure of the iron-based sprayed thin film for cylinder block of the present invention will be described with reference to the drawings.
FIG. 1 is an enlarged explanatory view showing an example of a cross-sectional structure of an iron-based sprayed thin film for a cylinder block according to the present invention. As shown in the figure, a cylinder block iron-based sprayed thin film 20 having a laminated structure in which a plurality of iron-based spray particles 22 are stacked in layers is formed on the cylinder bore surface 10a of the cylinder block base 10. Yes.
The particle diameter (r) in the film thickness direction indicated by the arrow X of the iron-based spray particles 22 is 30 μm or less, and the axial direction of the cylinder bore indicated by the arrow Y, that is, the particle diameter (R) in the piston sliding direction is 30. ˜300 μm.
When the particle size (r) in the film thickness direction of the iron-based spray particles is more than 30 μm, the cooling effect of the iron-based spray particles cannot be obtained, and the hardness (strength) of the iron-based spray particles itself is reduced. Destruction (peeling) occurs in the system spray particles.
Moreover, when the particle diameter (R) in the piston sliding direction of the iron-based spray particles is less than 30 μm, the contact area with the base becomes small, and the adhesion force due to the anchoring effect cannot be secured, and the cylinder block base material Separation occurs at the interface or between the iron spray particles.
On the other hand, when the particle diameter (R) in the piston sliding direction of the iron-based spray particles is more than 300 μm, the cooling effect of the iron-based spray particles cannot be obtained and the hardness (strength) of the iron-based spray particles itself is low. (The hardness of the iron-based material has a correlation with the cooling rate. If the film thickness is thick, the cooling rate becomes slow and sufficient hardness cannot be obtained.) Because it is low, it breaks in the grain during operation.) Occurs.

Moreover, in this invention, it is preferable that a film thickness is 100-380 micrometers.
When the film thickness is less than 100 μm, sufficient thin film strength may not be ensured, and destruction (peeling) may occur when a high load is repeatedly applied.
On the other hand, when the film thickness exceeds 380 μm, the internal stress of the thin film becomes high, and there is a possibility that destruction (peeling) occurs when a high load is repeatedly applied.

Furthermore, in the present invention, the film thickness may be uniform, but from the viewpoint that the internal stress in the thin film is relaxed, and the destruction (peeling) when a high load is repeatedly applied can be further suppressed. In particular, it is desirable to have regions A having a relatively small thickness and regions B having a relatively large thickness alternately in the axial direction of the cylinder bore.
At this time, the ratio (B / A) of the thickness of the region B to the thickness of the region A is preferably B / A = 1.3 to 7.5, and B / A = 1. More preferably, it is 5-3.5.

Here, FIG. 2 is an enlarged explanatory view showing another example of the cross-sectional structure of the iron-based sprayed thin film for cylinder block of the present invention. As shown in the figure, a cylinder block iron-based sprayed thin film 20 is formed on a cylinder bore surface 10 a of the cylinder block base 10.
The cylinder block iron-based sprayed thin film 20 has alternately a relatively thick region B and a relatively thin region A in the axial direction of the cylinder bore indicated by the arrow Y.
In the figure, A indicates the film thickness of the region A, and B indicates the film thickness of the region B.

Moreover, in this invention, it is preferable that hardness is HV300-500.
When the hardness is less than HV300, the thermal spray particles shrink, the contact area with the base becomes small, and the adhesion due to the anchoring effect cannot be sufficiently secured, and the fracture (peeling) occurs when a high load is repeatedly applied. Can occur.
On the other hand, when the hardness is higher than HV500, the thin film tends to become brittle, and for example, when the thin film is formed on the cylinder bore surface of the cylinder block base material and then honing is performed, the thin film may drop or peel off. .

Further, in the present invention, pores may be contained, but since the pores in the thin film are likely to be the starting point of cracks and peeling, the porosity is preferably low.
Specifically, the porosity is preferably 2.0% or less (area ratio in the sprayed section), and more preferably 1.0% or less (area ratio in the sprayed section).

Moreover, in this invention, it is preferable that content of iron oxide is 10 to 35% (area ratio in a thermal spraying cross section).
Since iron oxide in a thin film is likely to be the starting point for cracks and delamination, if its content exceeds 35% (area ratio in the sprayed cross section), destruction (peeling) may occur when high loads are repeatedly applied. There is sex.
On the other hand, when the content is less than 10% (area ratio in the sprayed cross section), there is a possibility that sufficient scuff resistance cannot be ensured.

Furthermore, in the present invention, the average roughness Ra of the surface corresponding to the cylinder bore inner surface is preferably 0.4 μm or less, and more preferably 0.3 μm or less.
When the average roughness Ra of the surface corresponding to the inner surface of the cylinder bore is more than 0.4 μm, the metal contact increases, which may cause an increase in friction with the piston or piston ring which is a sliding partner.
The average roughness of such a surface can be adjusted by, for example, forming a sprayed thin film and then performing a honing process.
The “surface corresponding to the inner surface of the cylinder bore” is a cylinder bore that can slide with a piston, piston ring, etc. when the iron block sprayed thin film for cylinder block of the present invention is formed on the inner surface of the cylinder bore of the cylinder block substrate. It is the surface on the inner surface side.

Furthermore, in the present invention, the oil retention depth Rvk in the surface roughness curve corresponding to the cylinder bore inner surface is preferably 0.2 to 2.0 μm, more preferably 0.5 to 1.8 μm. preferable.
When Rvk is less than 0.2 μm, the retention performance of the engine oil is lowered, which may cause a decrease in scuff resistance with the piston or piston ring that is the sliding partner.
On the other hand, when Rvk is more than 2.0 μm, the attacking property of the thermal spray coating increases, causing an increase in friction with the piston or piston ring that is the sliding partner, and the piston or piston ring that is the sliding partner. May increase wear of sliding parts.

Here, the oil retention depth Rvk in the roughness curve will be described with reference to the drawings.
FIG. 3 is a graph showing an example of a roughness curve. As shown in the figure, the slope is the smallest among the straight lines passing through two points (point A and point B) where the difference in tp value is 40% tp or more at the point on the roughness curve in the figure. A straight line is obtained, and the intersections of the straight line with the tp value 0% tp and tp value 100% tp are point C and point D, respectively, and the intersection between the cutting level passing through the point D and the roughness curve is point E. The intersection point of the roughness curve and the tp value of 100% tp is defined as a point F. At this time, the tp value is 100% tp so that the area surrounded by the line segment DE, the line segment DF, and the line segment EF is equal to the area of the triangle DFG. When the intersection point G is obtained, the distance between the point D and the point G is Rvk.

Next, the cylinder block of the present invention will be described in detail.
As described above, the cylinder block of the present invention is provided with the iron-based sprayed thin film for a cylinder block of the present invention.
That is, the cylinder block of the present invention has a cylinder block iron-based thermal spraying having a laminated structure in which a plurality of iron-based thermal spray particles are stacked in layers on the cylinder block base material and the cylinder bore inner surface of the cylinder block base material. A thin film.
Such iron-based spray particles have a particle diameter in the film thickness direction of the iron-based sprayed thin film for cylinder block of 30 μm or less, and a particle diameter in the axial direction of the cylinder bore of 30 to 300 μm.
By adopting such a configuration, the peel resistance is excellent.
In addition, in the iron-based sprayed thin film for cylinder block, as described above, the oil retention depth in the film thickness, film thickness distribution, hardness, porosity, iron oxide content, surface average roughness or surface roughness curve. In addition, the particle diameter of the iron-based spray particles constituting this can be appropriately adjusted.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

Example 1
On the surface of the base aluminum alloy, an iron-based alloy material (shape: wire, component: Fe-C alloy) is used to form an iron-based sprayed thin film by plasma spraying, and then a honing finish is performed. Thus, an iron-based sprayed thin film of this example was obtained.
When the cross section of the obtained iron-based sprayed thin film was observed with a scanning electron microscope (SEM) and a transmission electron microscope (TEM), the particle diameter in the film thickness direction of the iron-based sprayed particles constituting the thin film was 12 μm. Yes, the particle diameter in the axial direction of the cylinder bore of the iron-based sprayed particles is 200 μm, the film thickness of the thin film is 240 μm, and the film thickness is relatively large with respect to the film thickness A of the relatively thin area A of the thin film. The ratio (B / A) of the film thickness B of the thick region B was 3.6.
Further, when the hardness of the surface of the obtained iron-based sprayed thin film was measured with a Vickers hardness tester, the hardness of the thin film was HV355.
Furthermore, when the cross section of the obtained iron-based sprayed thin film was measured by image analysis, the porosity was 1.1%.
Further, when the obtained iron-based sprayed thin film was measured by image analysis, the content of iron oxide was 25%.
Furthermore, in the obtained iron-based sprayed thin film, when the surface roughness was measured with a surface roughness meter, the surface roughness Ra was 0.32, and the surface roughness calculated by the above-described method. The oil retention depth Rvk in the curve was 0.90. Table 1 shows the specifications of the iron-based sprayed thin film of this example.

( Examples 2 to 4, Reference Examples 5 to 15 and Comparative Examples 1 to 3)
The same procedure as in Example 1 was repeated except that the conditions of current, gas pressure and wire feed rate were changed in forming the iron-based sprayed thin film by plasma spraying, and the iron of this example having the specifications shown in Table 1 was repeated. A system sprayed thin film was obtained.

[Evaluation test]
(Peeling evaluation test)
The bore test piece cut out from the iron-based sprayed thin film in each of the above examples was subjected to a blast tester under the following test conditions, and the mass of the bore test piece before and after the blast test was measured. ) As an index of peel resistance. In addition, the amount of reduction in Example 1 was set to a reference value of 1.0 (the smaller the value, the better the peel resistance). The obtained results are shown in Table 2.

(Test conditions)
-Shape of bore test piece: 50 mm x 50 mm (wall thickness 5 mm)
・ Blasting particles: Alumina particles ・ Blowing amount: 50g / time, 5 times (total 250g)

  FIG. 4 is an explanatory side view showing the point of the peel evaluation test. As shown in the figure, the bore test piece 50 was placed on the fixing jig 100 and blast particles 102 were sprayed thereon.

(Scuff evaluation test)
The bore test piece cut out from the iron-based sprayed thin film in each of the above examples was subjected to a sliding test machine under the following test conditions, applied with a load of 10 kgf (= 98 N), and the frictional force sudden increase point was set as a ring scuff load. The obtained results are also shown in Table 2.

(Test conditions)
・ Sliding speed: 0.2m / s
・ Temperature: 25 ℃
・ Lubricant: 5W30SL (only initial application)
-Opposite sliding material: ring test piece (carbon steel is used as a base material and the sliding surface is coated with chromium nitride (CrN). Corresponds to a piston ring.)

  FIG. 5 is a perspective explanatory view showing the point of the scuff evaluation test. As shown in the figure, the ring test piece 104a was disposed on the bore test piece 50 and rotated while applying a load in the arrow Z direction.

(Friction evaluation test)
The bore test piece cut out from the iron-based sprayed thin film in each of the above examples was subjected to a reciprocating friction wear tester under the following test conditions, and the friction value was measured. The obtained results are also shown in Table 2.

(Test conditions)
・ Sliding speed: 0.5m / s
・ Temperature: 25 ℃
・ Pressing load: 10kgf (= 98N)
・ Test time: 1 hour ・ Lubricant: 5W30SL
-Opposite sliding material: Ring test piece (carbon steel is used as a base material and the sliding surface is coated with CrN. Corresponding to a piston ring.)

  FIG. 6 is a perspective explanatory view showing the point of the friction evaluation test. As shown in the figure, the ring test piece 104b was disposed on the bore test piece 50 and reciprocated in the arrow W direction while applying a load in the arrow Z direction.

From Table 1 and Table 2, it can be seen that Examples 1 to 4 belonging to the scope of the present invention have excellent peeling resistance as compared with Comparative Examples 1 to 3 outside the present invention.

It is expansion explanatory drawing which shows an example of the cross-section of the iron-type thermal spraying thin film for cylinder blocks of this invention. It is expansion explanatory drawing which shows the other example of the cross-section of the iron-type thermal spraying thin film for cylinder blocks of this invention. It is a graph which shows an example of a roughness curve. It is side surface explanatory drawing which shows the point of a peeling evaluation test. It is a perspective explanatory view showing the point of a scuff evaluation test. It is a perspective explanatory view showing the point of a friction evaluation test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cylinder block base material 10a Bore surface of cylinder block base material 20 Iron-type thermal spraying thin film for cylinder blocks 22 Iron-type thermal spraying particle 50 Bore test piece 100 Fixing jig 102 Blast grain 104a, 104b Ring test piece

Claims (8)

An iron-based sprayed thin film for a cylinder block, which is formed on the cylinder bore inner surface of the cylinder block substrate and has a laminated structure in which a plurality of iron-based sprayed particles are stacked in layers,
Contains pores, the porosity is 2.0% or less (area ratio in the sprayed cross section),
Containing iron oxide, the content of which is 10-35% (area ratio in the sprayed cross section),
The film thickness is 100 to 380 μm,
While having relatively thin regions A and relatively thick regions B in the axial direction of the cylinder bore, the ratio of the thickness of the region B to the thickness of the region A (B / A) is 1.3 to 7.5,
The hardness is HV300-500,
The average roughness Ra of the surface corresponding to the inner surface of the cylinder bore is 0.4 μm or less,
The oil retention depth Rvk in the surface roughness curve corresponding to the cylinder bore inner surface is 0.2 to 2.0 μm,
The iron-based sprayed particles have a particle diameter in the film thickness direction of the iron-based sprayed thin film for cylinder block of 30 μm or less, and a particle diameter in the axial direction of the cylinder bore of 30 to 300 μm. Iron-based sprayed thin film for blocks. While having relatively thin regions A and relatively thick regions B in the axial direction of the cylinder bore, the ratio of the thickness of the region B to the thickness of the region A (B / The iron-based thermal sprayed thin film for a cylinder block according to claim 1, wherein A) is 1.5 to 3.5. The iron block sprayed thin film for a cylinder block according to claim 1 or 2, wherein an average roughness Ra of a surface corresponding to the inner surface of the cylinder bore is 0.3 µm or less. The iron-based sprayed thin film for a cylinder block according to any one of claims 1 to 3, wherein the porosity is 1.0% or less (area ratio in a sprayed cross section). The cylinder block according to any one of claims 1 to 4, wherein the iron spray particles have a particle diameter in the film thickness direction of the iron block sprayed thin film for cylinder blocks of 5 to 30 µm. Iron-based sprayed thin film. 6. The iron system for cylinder blocks according to claim 1, wherein an oil retention depth Rvk in a roughness curve of a surface corresponding to an inner surface of the cylinder bore is 0.5 to 1.8 μm. Thermal spray film. The iron-based sprayed thin film for a cylinder block according to any one of claims 1 to 6, wherein the cylinder block substrate is made of an aluminum alloy. A cylinder block comprising the iron-based thermal sprayed thin film for a cylinder block according to any one of claims 1 to 7 .

Images