JPS581066A - Melt-sprayed surface layer - Google Patents

Abstract

PURPOSE:To form a melt-sprayed surface layer which has specific hardness and is excellent in its abrasion resistance and scuff resistance, by performing a plasma melt-spray of mixed powder consisting of ferromolybdenum powder of specific percentage, and a metallic carbide or metallic oxide powder. CONSTITUTION:A melt-sprayed surface layer on which a carbide or oxide particle whose hardness is >=Hu 800 has been dispersed is formed in an iron-molybdenum alloy, by performing a plasma melt-spray of a mixture consisting of 50-95% ferromolybdenum powder and 5-50% metallic carbide or metallic oxide powder. As for the ferromolybdenum powder, both high carbon and low carbon are available. As for the metallic carbide, for instance, a carbide of Cr, W, Si and B is available, and as for the metallic oxide, for instance, an oxide of alumina, titania, etc. is available. Also, as for the ferromolybdenum powder, it is desirable that its particle diameter is <= about 120mu.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal sprayed surface layer having excellent wear resistance, particularly 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 provide wear resistance. The hard chrome plating layer has high hardness,
Although it has excellent wear resistance, it has the drawbacks of requiring a long time for plating, lack of oil retention, and being prone to scuffing during sliding. 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. The surface layer sprayed with molybdenum is porous and has the advantage of good oil retention and scuff resistance. Since the wear resistance is low, it has the disadvantage that its wear resistance is inferior to that of a hard chromium plating layer.

In order to eliminate such drawbacks of the molybdenum thermal sprayed surface layer, thermal spraying is performed by thermal spraying a mixed powder obtained by adding and mixing molybdenum powder with self-fluxing alloy or/and metal carbide or oxide powder. Surface layers have been proposed, some of these with considerable success.

However, when lubricating oil containing carbon sludge and dust from partially incomplete combustion of fuel is used, the above-mentioned resistance to so-called abrasive wear, in which these act as abrasive agents and wear piston rings and cylinder liners, is lower. The sprayed surface layer is not satisfactory (・
0 This problem has been solved, without compromising scuff resistance.
As a thermal sprayed surface layer with even better abrasive wear resistance, the applicant has already plasma sprayed a mixed powder consisting of a high carbon ferrochrome powder containing 15 to 60% molybdenum powder and the balance 60 to 70% chromium. (Japanese Patent Application No. 54-1279)
051 wear-resistant thermal sprayed surface layer).

The object of the present invention is to provide an improved thermal sprayed surface layer having even better abrasive wear resistance and scuffing resistance than the thermal sprayed surface layer according to the above-mentioned Japanese Patent Application No. 54-127905. 95%, metal carbide or metal oxide powder 5-501,! . It is formed by plasma spraying a mixed powder consisting of iron-molybdenum alloy with metal carbide or metal oxide particles having a hardness of I(v800 or higher) dispersed in it.It has excellent wear resistance and scuff resistance. Regarding the surface layer.

The sprayed surface layer of the present invention is formed by plasma spraying. Plasma spraying is advantageous because it can provide a high-temperature spraying flame and can easily melt wear-resistant powder materials with high melting points to form a sprayed surface layer with strong bonding strength.

The ferromolybdenum powder used as thermal spraying material is JI
Pulverized ferromolybdenum specified in SG 2307r Ferromolybdenum-1 can be used.

The JIS standard specifies high carbon ferromolybdenum and low carbon ferromolybdenum, and either of them may be used.

Metal carbides or metal oxides are dispersed in the sprayed surface layer to form hard spots and contribute to wear resistance, but if the hardness exceeds Hv800, the effect of improving wear resistance is insufficient. Such metal carbides and metal oxides include
Examples include carbides of chromium, tungsten, silicon, and boron, and oxides of alumina and titania.

If the particle size of the thermal spraying material powder is too coarse, the porosity of the thermal spraying surface layer will become too high, reducing the bonding strength of the thermal spraying surface layer and adhesion to the base material, and hard carbides and oxides will fall off. This becomes an abrasive agent and increases wear. These particle sizes are approximately 125 μ (120 mesh)
The following is preferable.

Pores are formed in the sprayed surface layer, which provides oil retention and contributes to scuff resistance, but as mentioned above, it is better not to have too many pores (the porosity should be 30% by volume or less). is good.

Next, an experimental example will be explained.

Wear Test (Part 1) 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 mixed powder was combined and slid on cylinder cast iron (Fe12).

The blending ratio of the thermal spray mixed powder is as shown in Table 1.

Ferromolybdy (re-Mo) is 0.04% C, 65
, 96% MO1 is obtained by pulverizing low carbon ferromolybdenum, the remainder of which consists of Fe and impurities. The particle size of ferromolybdenum powder is 10-105μ, chromium carbide (Cr3C2) powder is 10-74μ, Cr3C2
It has a hardness of Gi llv 1300.

Table 1 (% by weight) These mixed powders were thermally sprayed onto the square end faces of 5m+xx 511x10 prismatic cast iron test specimens to give a thickness of 1.
A sprayed surface layer of fl 1 m was formed and polished to a thickness of 0.511. The thermal spraying conditions are as follows.

Gun used: Metco 3MB plasma spray gun
Flow: 450 to 500 A Voltage: 61 V Gas used: argon, hydrogen mixed gas Argon 100 ft/hr, hydrogen 13 ft3/hr Abrasion test of the sprayed surface layer was conducted on these test pieces.

The test apparatus is schematically shown in FIG.
An Fe12 disc (mating material) with a diameter of 80 mm and a thickness of 1111 mm is removably attached to the stator holder (1).
2) is filled with lubricating oil from the back side through the oil filling hole (3). A predetermined pressure is applied to the stator holder (1) by a hydraulic device (not shown) in a direction toward the right in the figure. A rotor (4) is provided opposite to the disk (2), and is rotated at a predetermined speed by a drive device (not shown). A test specimen holder (5
), the four test pieces (6) manufactured as described above are removable at equal intervals on a concentric circle, and the sprayed surface layer (6a) is made to slide against the disk (2). It is installed on. Figure 3 shows a partially enlarged view of the area around the test piece. In such a device, a predetermined pressing force is applied to the stator holder (1), and the disc (mate 1) (2+ and the thermal sprayed surface layer (6a) of the test piece (6) are separated by a predetermined surface pressure. The rotor (4) is rotated while being in contact with each other, and the sliding surface is supplied with oil from the oil supply hole (3) at a predetermined oil supply speed.

With such a testing device, the contact surface pressure is 100 kg/c.
Friction speed 8m/5eC1 Friction distance 200 km, '
The thermal sprayed surface layer (6a) and the disc (2) were made to slide on each other under the conditions of lr4 lubricating oil supply rate of 0.41/m group and oil temperature of 80°C, and the amount of wear of both was measured. 4000 rpm, 60 for lubricating oil
A lubricating oil containing significant carbon sludge was used for a 50 hour diesel engine bench test at full horsepower load. In Figure 1, the amount of wear on the sprayed surface layer is the amount of decrease in thickness, and the amount of wear on the mating disk is the radial cross-sectional area of the groove-shaped wear scar caused by sliding with the test piece. It represents.

From the same figure, it can be seen that the greater the amount of C[3C2 powder in the thermal spray mixed powder, the more the wear of the mating cast iron material increases, and the amount of orientation becomes 50%.
%, the wear of the mating cast iron material increases rapidly. The wear of the sprayed surface layer decreases rapidly when the blending amount of Cr3C2 powder reaches 5%, but when the blending amount is in the range of 5 to 60%, the wear of the sprayed surface layer gradually increases until it exceeds 60%. It can be seen that the wear of the sprayed surface layer increases rapidly. The reason is that the blended amount of Cr3C2 powder is 60%.
If the value exceeds , the bonding strength of the sprayed surface layer will suddenly weaken.
During sliding, Cr3A2 particles from the sprayed surface layer became noticeable, and the dropped Cr3C particles interacted with the abrasive agent to abrade not only the mating cast iron material but also the sprayed surface layer. This is because from the above test results,
It can be said that the blending amount of hard metal carbide or metal oxide powder such as Cr3C2 is preferably within the range of 5 to 50%.

Wear Test (Part 2) The thermal sprayed surface layers A and B of the present invention, which are formed by thermal spraying the mixed powder having the composition shown in Table 2, and the comparative surface layer shown in the above-mentioned Japanese Patent Application No. 1973-
127905, a molybdenum sprayed surface layer D formed by spraying molybdenum wire with an oxygen-acetylene flame.
, and the hard chromium plating layer E, the above wear test (
The same test as in Part 1) was conducted. However, the wear rate was 3.
．． It was taken at 5.8 m/Sec. The ferromolybdenum powder was made by Ronodo, the same as that used in the wear test (part 1). Cr, C2 powder and A/, 0.
The particle size of the powder is 10 to 74μ, and the hardness of the former is HV.
1300, the latter being 11v 1-icro.

Table 2 (Weight: C) Note: A and B are the sprayed surface layers of the present invention, and C, D, and E are the comparative coating surfaces.

The test results are shown in FIG. Number 3.5 in the diagram
and 8 indicate the friction speed m/sec, respectively. From the figure, it can be seen that the thermal sprayed surface layer of the present invention is not only a hard chromium plating layer, but also a hard chromium plating layer, as compared to the molybdenum thermal sprayed surface layer.
It can be seen that both the wear of the sprayed surface layer and the wear of the mating material are smaller than that of the sprayed surface layer according to the above, and the wear resistance is further improved.

Scuff test A scuff test was conducted on the surface layers shown in Table 2 using the testing apparatus (FIGS. 2 and 3) used in the abrasion test. The test method is as described below. 80°C motor oil #30 as lubricating oil at 0.46/mi
F' shown in Fig. 3 was obtained by setting the contact surface pressure to 40 kg/c% and the friction speed to l'3 rri/see.
The surface layer (6) of the C25 mating disk (2) and the test piece (6)
a), and increase the contact pressure to 10k every 3 minutes.
The surface layer ( 6a)
The stator holder (
The torque (torque generated by friction) T generated in 1) is applied to the load cell (8) via the spindle (force), and its change is read by the dynamic strain meter (9) and recorded by the recorder 00).

Assuming that scuffing occurs when the torque T suddenly increases, the contact surface pressure at that time is taken as the scuffing surface pressure, and the quality of the scuffing resistance is determined based on the magnitude of this.

The test results are shown in Table 3.

From Table 3, it can be seen that the thermal sprayed surface layer of the present invention has improved scuffing resistance compared to the comparative surface layer (.

As explained above, the thermal sprayed surface layer of the present invention has further improved wear resistance and scuff resistance compared to the chromium plating layer, which has excellent wear resistance, and the molybdenum thermal sprayed surface layer, which has excellent scuff resistance. The material used is ferromolybdenum, which is much cheaper than molybdenum, so the strike is low and the industrial value is high (・0

[Brief explanation of drawings]

1 and 5 are graphs showing the results of the wear test. Figure 2 is a vertical cross-sectional view showing an outline of the test equipment used in the wear test and scuff test, Figure 3 is a partially enlarged view of Figure 2,
FIG. 4 is a side view taken in the direction of the IV-■ arrow shown in FIG. Figure 1 ■ Figure 3 2 ra 6 ri b Figure 5

Claims (1)

[Claims] A metal carbide or metal oxide formed by plasma spraying a mixed powder consisting of 50 to 95% ferromolybdenum powder and 5 to 50% metal carbide or metal oxide powder, and having a hardness of 1 vsoo or more in an iron-molybdenum alloy. A thermal sprayed surface layer with dispersed particles that has excellent wear resistance and scuff resistance.