JPS5937735B2 - Wear-resistant sintered alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintered alloy suitable as a material for sliding parts that requires wear resistance, and which is made of S t 3 N
The object of the present invention is to provide a sintered alloy with improved wear resistance by dispersing the hard particles of No. 4.

It has been well known that one method of improving the wear resistance of a sintered alloy is to disperse hard particles such as various carbides, oxides, nitrides, and intermetallic compounds into the sintered alloy.

These hard particles have a large effect on wear resistance, but the reason why they are fully effective is because the hard particles dispersed on the friction sliding surface are firmly held by the base metal matrix and do not fall off. is necessary.

In general, these hard particles are themselves brittle or have poor sintering properties with the metal matrix, so they tend to fall off from the metal matrix, and adding hard particles alone is not necessarily effective in improving wear resistance. The hard particles that cannot be used and instead fall off increase the wear of the sintered alloy itself due to the abrasive abrasive action σ, and have a large effect on the wear of the mating friction surface.

The present invention aims to improve the above-mentioned drawbacks and provide a wear-resistant sintered alloy that has excellent wear resistance and is also economical.

The alloy of the present invention is produced in the following manner.

Weight arm Si3N4; 0.5-10%, Ni; 0.5
~5.0%, C: 0.2~1.2%, and the balance is iron.The powders are mixed together, and then press-molded and sintered.

Although this alloy has excellent wear resistance as it is, it is further added to the matrix composition (one or more of CaF2, BaF2, and LiF, which have lubricating properties, in a total amount of 2 to 8 Contains 1 to 10% by weight of low melting point metals such as lead, indium, bismuth, and tin, or 0.5 to 4% by weight of sulfides such as WS2 and Mo82, and has lubricity. This has the effect of reducing frictional resistance and further reducing the amount of wear on the mating material.

The reasons for selecting the composition range etc. will be described below.

All percentages below indicate weight.

Silicon nitride (S h 3N, i 'ii is a hard particle that is relatively inexpensive, has high hardness, and has high mechanical and thermal impact strength. It is added to improve wear resistance, and the amount added is 0.5 to 10
% is appropriate.

If the amount added is less than 0.5%, the effect will not be fully exhibited and the effect of improving wear resistance will be small.

If the amount added is 10% or more, the strength of the sintered material itself will be weakened, and the wear and tear of the mating material will increase.

As mentioned above, 813N4 of the present invention also requires S l as hard particles dispersed on the friction surface in order to achieve its full effect.
3 It is necessary for N4 to be firmly held in the base metal matrix so that it does not fall off, but as a result of various studies, the present invention has developed a method using iron as the metal matrix and hard particles of S
It has been found that the addition of nickel is extremely effective in improving the bonding properties of i3N4.

Nickel is often added in powder metallurgy for the purpose of improving sinterability and strength, but in the present invention, in addition to strengthening the matrix, Fe is added to a part of the S13'N4 particle surface.
- Promote the formation of the 8i reaction layer, matrix and St
3N4% has the effect of significantly improving the bonding properties with the molecule.

If the amount of Ni added is less than 0.5%, the effect is small;
% or more, the matrix is hardened more than necessary, so the preferred range is 0.5 to 5.0%.

Carbon dissolves in iron, strengthens the iron matrix, and contributes to improving heat resistance and wear resistance, but if it is less than 0.2%, the effect is insufficient, and if it exceeds 1.2%, the amount of cementite increases. increases, making the material brittle, so the addition range is 0.2 to 1.
．． 2%.

The sintering temperature of the alloy according to the invention is selected between 1080°C and 1230°C.

If the sintering temperature is below 1080°C, the reaction between the matrix and 813N4 will not be sufficient, and if it is above 1230°C, a liquid phase of Fe-8i, which is the main reaction product, will be produced, so the decomposition of 5i3N4 will be extremely resistant. This is not preferable since the abrasion resistance is rather reduced and the dimensional accuracy is also deteriorated.

The particle size of the 5i3N4 powder is optimally in the range of 160 mesh to +350 mesh.

If the mesh is more than 60, the mating friction surface will be damaged.

In addition, if the mesh is less than 350, Fe-8i3N4 during sintering
It is difficult to control the reaction, and this tendency becomes more pronounced as the amount of 5i3N4 added increases or as the sintering temperature increases.

Addition of a lubricious fluoride such as CaF2, BaF2, or LiF has the effect of reducing frictional resistance and reducing wear on the mating friction surface.

Since Ca F 2 , B a F 2 , and LiF exhibit very similar behavior during friction, they may be added alone, or two or more of them may be added at the same time.

If the total amount of addition is less than 2 times, the effect of addition will be small, and 8
% or more, compression moldability is inhibited and material strength decreases, so the preferred range is 3 to 8%.

Pb has low shear strength, and In, Bi, Sn, C
It is a metal that has lubricating properties along with d, Se, etc.
As a result of the frictional action, some of the Pb on the friction surface becomes molten or oxidized into the form of PbO, which further increases its lubricity and prevents the phenomenon of adhesion between the sintered alloy and the mating friction surface. This has the effect of reducing frictional resistance and wear.

However, if it is less than 1%, the effect is small, and if it is more than 10%, the material strength decreases, so the preferred range is 1 to 10%.

A sulfide having lubricating properties such as WS2 or MoB2 also has the same effect as the above-mentioned fluoride addition.

If the amount added is less than 0.5%, the effect is insufficient, and 4%
As mentioned above, since the dimensional change during sintering is large, the preferable range is set to 0.5 to 4.0%.

Example 1 S3N4 powder with 1100+350 mesh, Ni powder with average particle size of 3μ, F''e powder with -100 mesh, and graphite with -300 mesh were mixed into the composition shown in Table 1 and molded at 517d pressure. After 1050℃ or 1150℃
Friction and wear tests were conducted on the sintered bodies obtained by sintering at ℃ for 30 minutes in a reducing atmosphere under the test conditions shown in Table 2.

The test results are summarized in Tables 3 and 5.

It is clear from the above results that the alloy of the present invention has excellent wear resistance.

Example 2 A sample obtained by blending the composition shown in Table 4 in the same manner as in Example 1, molding at 5 t/d pressure, and sintering at 1150°C for 30 minutes was prepared in Example 1.
Similarly, a friction and wear test was conducted under the test conditions shown in Table 2 (Table 5), and the results are shown in Table 5.

Example 3 The following formulation was treated and sintered in the same manner as in Example 1, and tested under the test conditions shown in Table 2. The results were as follows.

■ Fe-2Ni-0,2C-4Si3N4-3BaF
2■ F e-2N i -1, 2C-4S i 3
N4-IMo 82 test results Density Hardness Crushing strength Wear amount -

Claims (1)

[Claims] 1 Weight: Si3N4; 0.5-10%, Ni;
A wear-resistant sintered alloy containing 0.5 to 5.0%, C; 0.2 to 1.2%, and the remainder substantially consisting of iron. 2 813 N4 with weight receiver; 0.5-10%, Nl
; 0.5-5.0%, C; 0.2-1.2%, Ca
A wear-resistant sintered alloy containing a total of 2 to 8% of one or more of F2, B a F2, and LiF, with the remainder substantially consisting of iron. 3 wt% Si3N4; 0.5-10%, N
i; 0.5-5.0%, C; 0.2-1.2%, lead,
A wear-resistant sintered alloy containing a total of 1 to 10% of one or more low-melting point metals such as indium, bismuth, and tin, and the remainder being substantially G-iron. 4 5t3N at the weight receiver; 0.5-10%, to i;
0.5-5.0%, C; 0.2-1.2%, W S 2
．． One or two types of M o S 2 in total 0.5
~4%, with the remainder consisting essentially of iron.