JPS5946303B2 - thermal spray surface layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermally sprayed surface layer having particularly excellent wear resistance, and more specifically to a plasma sprayed surface layer having excellent abrasive wear resistance and scuff resistance.

For example, in mechanical parts such as piston rings and cylinder liners that slide at high speed, hard chrome plating has been widely used on the sliding surfaces to impart wear resistance.

However, although the hard chrome plating layer has high hardness and excellent wear resistance, it has the drawbacks of requiring a long time for the plating process, lack of oil retention, and being prone to scuffing during sliding. have. Therefore, in recent years, a molybdenum sprayed surface layer has been partially adopted in place of the hard chromium plating layer as a surface layer with improved scuff resistance.
In this case, the surface layer sprayed with molybdenum is porous and has the advantage of good oil retention and scuff resistance. It has the disadvantage that its wear resistance is inferior to that of a hard chrome plated layer. In order to eliminate such drawbacks of the molybdenum sprayed surface layer, a sprayed surface layer is made by spraying a mixed powder obtained by adding and mixing self-fusing alloy and/or metal carbide or oxide powder to molybdenum powder. have been proposed, and some of these have achieved considerable success.

However, when lubricating oil containing carbon sludge and dust from partially incomplete combustion of fuel is used, it is difficult to resist so-called abrasive wear, where these act as abrasive agents and wear piston rings and cylinder liners. I haven't found anything that satisfies me yet. The purpose of the present invention is to provide a thermal sprayed surface layer that has even better abrasive wear resistance without compromising scuff resistance. Nickel-chromium alloy powder (i.e., self-fusing alloy powder) containing less than % by weight is added to molybdenum powder of approximately the same particle size so that the total amount is 15 to 60% by weight based on the entire thermal sprayed material, and The present invention relates to a thermal sprayed surface layer formed by thermal spraying a thermal spraying material made of a mixture whose main component is ferrochrome powder containing 60 to 70% by weight of chromium based on the total weight.

Here, the expression "as the main component of the remainder" includes not only the case where the ferrochrome powder occupies most of the remainder, but also the case where the ferrochrome powder occupies 100% of the remainder. The sprayed surface layer according to the invention is preferably formed by plasma spraying.

Plasma spraying is advantageous because it can provide a high-temperature spray flame, and therefore can easily melt wear-resistant powder materials with high melting points to form a sprayed surface layer with strong bonding strength.
In the present invention, the blending amount of molybdenum powder and nickel chromium alloy powder is 15 to 60% by weight based on the entire thermal spray material.
The reason for limiting the amount is that if the amount is less than 15% by weight, the seizure resistance will be significantly impaired and the wear of the mating material will increase. On the other hand, if the blending amount exceeds 60% by weight, although the seizure resistance is improved, the hardness of the sprayed surface layer decreases, and the abrasive agent is absorbed into the sprayed surface layer during lubricated sliding with the abrasive agent present. This increases the wear of the sprayed surface layer itself and the mating sliding material. It is particularly preferable that the molybdenum and nickel-chromium alloy powder be blended in an amount of 25 to 50% by weight. Ferrochrome powder containing 60 to 70% by weight of chromium, for example, crushed high carbon ferrochrome, is used; however, if the chromium content is less than 60% by weight, the hardness of the sprayed surface layer decreases and the abrasive wear resistance decreases. to degrade.

On the other hand, if the chromium content exceeds 70% by weight, too much fine powder will be produced during pulverization, making it unsuitable as a thermal spray material.
Note that low carbon ferrochrome has relatively low hardness, low abrasive wear resistance, and is not easy to crush, so high carbon ferrochrome is better. Therefore, 0 of the high carbon ferrochromes specified in JISG23O3 "Ferrochrome"
You can use it by crushing it from No. 4 to No. 4.

What is the particle size of molybdenum powder, Niskelium chromium alloy powder containing boron, carbon, silicon, and iron (self-soluble elements), and high carbon ferrochrome powder? -170~325
Preferably mesh.

However, -170 to 325 mesh is used here to mean a range that passes through a 170 mesh sieve but does not pass through a 325 mesh sieve. If the particle size is coarser than 170 mesh, there will be too many pores in the sprayed surface layer, impairing abrasive wear resistance.On the other hand, if it is finer than 325 mesh, it will be easily oxidized during thermal spraying, and these oxides will form in the sprayed surface layer. It accumulates inside the surface and deteriorates the mechanical strength, and the number of pores becomes too large, impairing the abrasive wear resistance. Further, Japanese Patent Application No. 1983-127905 filed by the present applicant relates to a wear-resistant thermal sprayed surface layer made of a thermal sprayed material in which molybdenum powder is added to high carbon ferrochrome powder at a weight ratio of 15 to 60%. However, the thermal spray material according to the present invention further adds Niskelium chromium alloy powder containing a self-fusing element to increase the metallic wettability between the molybdenum powder and the high carbon ferrochrome powder, and improves the density of the entire thermal spray coating. The purpose of this is to further improve abrasion resistance.

For this reason, it is essential that the amount of self-soluble elements added be 8% by weight or less. As this self-fusing alloy, JISH
MSFNi system standardized to 83O3 can be used. Next, the present invention will be explained using experimental examples.

Wear Test Figure 1 shows an example of the results of an abrasion test in which a sprayed surface layer obtained by varying the blending ratio of the sprayed material was combined with cast iron for a cylinder, and the cylinder was made to slide.

The blending ratio of the thermal spray material and each element contained in this blending ratio are
The weight ratio is shown in the table. The particle size is -170 to 325 mesh.

Ferrochrome powder is JISG23O3 [Ferochrome]
A pulverized high carbon ferrochrome No. 3 specified in the following was used. In Table 1 above, the composition of the self-fusing alloy powder is Cr: 17%, B: 3.2%, Si: 4%, F
e: 4%, C: 0.8%, balance Ni.

These mixed powders were thermally sprayed onto the square end faces of prismatic cast iron test pieces measuring 511 x 511 x 10 mm, and polished to form a sprayed surface layer with a thickness of 0.31 Lm.

The thermal spraying conditions are as follows. Used by Ganri Metco 3
MB plasma spray gun nozzle: GH current: 470-50
0A, Voltage: 64V Gas used: argon, hydrogen mixed gas argon 100ft3/h! - Hydrogen 10ft3/Hr Abrasion tests on the sprayed surface layer were conducted on these test pieces.

The main parts of the test machine are schematically shown in Figure 2a.
diameter 80 removably mounted on stator holder 1
11, thickness 11m1f) Lubricating oil is applied to the center of the disk 2 made of FC25 from the back side through the oiling hole 3. Also,
A hydraulic device (not shown) applies a pressing force to the stator holder 1 toward the right in the figure at a predetermined pressure. Four test pieces 6 are fitted into holes carved at equal intervals on the concentric circle of the rotating shaft of the test piece holder 5 fitted to the rotor 4 on the disk 2, and these test pieces The thermally sprayed surface layer 7 of the piece 6 is brought into contact with the disk 2, and further rotated at a predetermined speed by a drive device (not shown). With such a testing machine, the contact pressure 1
00k9/d, friction speed 5m/Sec, friction distance 200
The thermal sprayed surface layer 7 and the disk 2 were allowed to slide against each other under conditions of a lubricating oil supply amount of 0.41/Mn, and an oil temperature of 80° C., and the amount of wear of both was measured. For lubricating oil, 4000 rpm, 6
A lubricating oil containing significant carbon sludge was used for a 50 hour diesel engine bench test at 0 horsepower full load. For comparison, FIG. 1 also shows the results of a similar test conducted on a hard chrome plating layer.

In the figure, the amount of wear of the sprayed surface layer 7 is the amount of decrease in thickness,
The amount of wear on the disk 2, which is the mating material, is expressed by the cross-sectional area of the groove-like wear scar caused by sliding with the test piece 6. From the same figure, Ni-Cr is mainly composed of MO powder and contains self-soluble elements.
An alloy powder containing 15 to 60% by weight has excellent abrasive wear resistance, and a composition containing 25 to 50% by weight gives better results than a hard Cr plating layer.

Furthermore, even when compared with Japanese Patent Application No. 127905/1982, the abrasion of the thermally sprayed surface layer 7 according to the present invention, which improves the density of the thermally sprayed coating, shows good results. Structure observation Among the formulations in Table 1 above, Ni- containing MO + self-soluble elements
A mixed powder containing 25% by weight of Cr powder and 75% by weight of Fe-Cr powder was heated to a size of 85mm x 2.2m77 under the same conditions as above.
X3. A secondary image taken with a scanning electron microscope of the surface of the sprayed layer, which was thermally sprayed into an annular groove with a width of 1.9m1L and depth of 0.18mm cut into the outer peripheral surface of an Omm cast iron piston ring and polished. The third electronic image (magnification: 800x x 5/9)
As shown in the figure.

Figure 4 is a CrKα X-ray image taken by an X-ray microanalyzer at the same location as in Figure 3, Figure 5 is the same FeKa X-ray image,
FIG. 6 similarly shows a MOLα X-ray image, and FIG. 7 shows a Kα X-ray image of Ni and Cr containing self-soluble elements. However, the seventh
The CrKα-ray X-ray image in the figure overlaps with that in FIG. 3 and cannot be clearly distinguished. From these, the gray area in Figure 3 is approximately Fe.
-Cr, it can be seen that the white phase distributed therein is MO, and it can be seen that the Ni-Cr alloy containing self-soluble elements is also well distributed in appropriate places. Seizure Resistance Test A scarf test was conducted on the same test piece as used in the abrasion test using the same testing machine.

In Figure 2 a, the sprayed surface layer 7 of the test specimen 6 and the disc 2
The contact pressure is 50kg/Crii, and the friction speed is 8m.
/Sec, slide the motor oil #30 heated to 80°C through the oil filling hole 3 while supplying 350cc/min, and increase the contact pressure by 10kg/Cd every 3 minutes, so that the thermal sprayed surface layer 7 and The torque (frictional force) F generated in the stator holder 1 due to the friction between the disk 2 and the disk 2 is transferred to the load cell via the spindle 8 as shown in FIG. 9, the change was read by an axial strain meter 10, and recorded by a recorder 11. Thus, it was assumed that scuffing occurred when the torque F suddenly increased, and the contact pressure at this time was compared to evaluate the scuffing resistance. The test results are shown in FIG.

As in the abrasion test described above, the same figure also shows the results of a similar test conducted on a hard chromium plating layer for comparison. From the same figure, the main component is MO powder, and Ni-Cr
It can be seen that the smaller the amount of alloy powder mixed, the worse the seizure resistance becomes.

In particular, when the amount is less than 15% by weight, the seizure resistance deteriorates rapidly, and when it is less than 10% by weight, it becomes inferior to a hard Cr plated layer. From the above experiments, the greater the amount of powder-free blending of the main MO component, the better the seizure resistance, but considering the abrasive wear resistance mentioned above, it is recommended that the blending amount ranges from 15 to 60% by weight. I understand. Within this range, although the scuff resistance is inferior to that of conventional molybdenum sprayed surface layers, the difference is not large and is sufficient as a sliding surface for sliding parts such as piston rings and cylinder liners in internal combustion engines. This is a satisfactory level. Further, the blending amount is particularly preferably in the range of 25 to 50% by weight.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the results of the abrasion test, and FIG. 8 is a graph showing the results of the scathing test. Figure 2a is a partial vertical sectional view schematically showing the main parts of the testing machine used for the wear test and the scathing test, and Figure 2b is Af)I-
It is a 1 arrow side view. FIG. 3 is an electron micrograph (magnification: 800 times) showing the structure of the sprayed surface layer according to the present invention formed on the outer peripheral surface of the piston ring. FIGS. 4 to 7 show Cr. Fe. M.O. It is an X-ray photograph showing the distribution state of each element of Ni. In addition, in the symbols used in the drawings, 2
......Mating material disc, 6...Test piece, 7.
...This is a thermal sprayed surface layer.

Claims (1)

[Claims] 1 Nickel-chromium alloy powder containing boron, carbon, silicon, and iron in a total amount of 8% by weight or less based on the entire thermal sprayed material is added to molybdenum powder of approximately the same particle size, and the total amount is added to the total amount based on the entire thermal sprayed material. A thermal spraying surface layer formed by thermal spraying a thermal spraying material consisting of a mixture of ferrochrome powder containing 15 to 60% by weight and 60 to 70% by weight of chromium based on the entire thermal spraying material, with the remainder being the main component.