SU1502198A1 - Method of applying a coating on the surface of sintered blanks - Google Patents

Abstract

The invention relates to powder metallurgy, in particular, to methods for applying lubricating coatings. The goal is to increase the coating thickness and increase the stability of properties. A billet and a tumbling mixture in the amount of 30-50% by weight of the billet, consisting of iron and graphite, taken in a ratio of 9: 1-8.5: 1.5, are placed in the mixer, and the tumbling is carried out for 1-2 hours The method allows to increase the stability of the properties of powder materials obtained by double pressing and sintering. 2 tab.

Description

one

(21), 4295551 / 23-02 (22) 08/11/87 (46) 08/23/89. Bksh. No. 31 (72) N.V.Russkikh and N.A.Sidorbv (53) 621.762.02 (088/8)

(56) USSR Author's Certificate and 181946, cl. C 23 C 17/00, 19b6.

Technological instructions ABA25.065.00013, 1978.

(5A) METHOD OF DRAWING COATINGS ON THE SURFACE OF SPECIAL BLOCKS

(57) The invention relates to powder metallurgy, in particular to methods for applying lubricating coatings. The goal is to reduce the thickness of the coating and increase the stability of the properties. Place the billet and tumbling mixture in the amount of 30-50% by weight of the billet, consisting of iron and graphite, taken in a ratio of 9: 1-8.5: 1.5. and carry out tumbling for 1-2 hours. The method allows to increase the stability of the properties of powder materials obtained by double pressing and sintering. 2 tab.

The invention relates to powder metallurgy, in particular to methods for applying lubricating coatings, and can be used in the double pressing and sintering of powder blanks.

The purpose of the invention is to increase the coating thickness and increase the stability of properties.

The method is carried out as follows.

A billet and a tumbling mixture in the amount of 30-50Z by weight of the blanks, consisting of iron and graphite, taken in a ratio of 9: 1-8.5: 1.5, are placed in the mixer, and the tumbling is carried out for 1-2 hours

When tumbling in a mixture of iron powder with graphite, burrs and sharp edges are removed due to abrasion with iron powder, and the surface of the blanks and pores are uniformly coated with graphite by adhesion. during high-temperature sintering, graphite dissolves and compensates for the loss of carbon in the surface layer, which inevitably occurs during high-temperature sintering of powder blanks. The absence of burrs ensures the accuracy of placing the blanks in the die cavity and eliminates instances of tool breakage. The process of trimming the blanks is carried out for 1-2 hours. The hardening of such blanks leads to an increase in the hardenability and stability of the hardness values. During the second pressing, a layer of graphite lying on the surface of the blanks lubricates the cavity of the matrix and reduces wear. When the content of graphite in the mixture is less than 1 part and the increase in the iron content is more than 9 parts, the coating effect decreases. In this case, the coating layer decreases and a decarbonized layer takes place on the blanks after sintering and the scatter of hardness values is preserved.

g

31 302

Inspection: The initial content of 1 rp. Klisna more than 1.5 leads to a decrease in the concentration of the iron powder and its content is not sufficient to conduct the abrasion of sharp edges and burrs. and the surface of the workpieces, the productivity of the flashing operation affects the penetration depth of the graphite. The optimal time for tumbling is 1-2 hours, and a maximum possible film of a coating of 20-25 µm is formed on the surface. With a hapton lasting less than 1 hour, the layer becomes insignificant, less than 20 microns; therefore, the billets, after sintering and subsequent quenching, retain low hardenability and a large scatter of solid matter.

An increase in the duration of tumbling more than 2 hours does not give a significant increase in the thickness of the film; therefore, carrying out tumbling more than 2 hours is impractical. Achieving the maximum possible coating thickness of 25 microns makes it possible to significantly reduce the spread of hardness and increase the hardenability, and a further increase in the layer is economically inefficient.

Example 1. Prepare a tumbling mixture of waste iron powder fraction of 0.2-0.3 mm and graphite pencil fraction less than 0.2 mm. Billets of the 30I12M grade with a density of 6.5 g / cm, sintered at a temperature of 1150 ° C, are placed in a cone blender and tacked according to the modes given in the table. After that, they are pressed at a pressure of 8 t / cm and subjected to a second sintering at 1230 ° C and quenched in oil. Hardenability assess- HHBajoT based on measurements of the torus

Powder Fe 9 Stearate n 1 Powder Fe 9 Gy afit 1

Powder Fe 8.5 Graphite1,5

Proposed

0

five

0

50

five

Reached, Rechu. iMTi) tests are shown in Table B. one .

Example 2. The modes of preparation of the blanks and the compositions of the tumbling mixtures are the same as in example I, but a lubricating coating is applied on the blank of material GPR-1.

The test results are shown in table 2.

From the tables it can be seen that the depth of coating increases with the increase in the length of tumbling and the concentration of graphite in the mixture. The best hardenability and stability of hardness are obtained when tumbling for 1-2 hours with a ratio of iron powder and graphite of 9: 1-8.5: 1.5. In this case, a uniform coating of 25 µm depth is obtained, the hardening is greatest with a minimum dispersion of hardness values. An increase in the concentration of graphite leads to the fact that, when tumbling, the workpiece in such a mixture does not need to be rubbed due to a decrease in the volume of the iron powder mixture. As a result, the burrs and sharp edges are not completely removed from the surface of the blanks.

Claims (1)

Invention Formula The method of coating the surface of sintered workpieces, which includes the tumbling of workpieces in a mixture of iron with a solid lubricant, taken in an amount of Gp-50% by weight of the workpieces, characterized in that, in order to increase the thickness of the coating and increase the stability of properties, as a solid lubricant graphite is taken when the ratio of iron to graphite 9: l is 8.5: l, 5, and tumbling is carried out for 1-2.4.  Table 1 28-40 31-40 32-40 36-42 31-42 34-43 37-44 37-45 Fe9 powder Stearate1 Fe9 powder GraphiteI Re8,5 powder Graphite1,5 Compiled by I. Poymenova. I. Gorn Editor. Tehred L. Oliynyk. Corrector S. Cherni Order 5006/14 Circulation 711 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushyka nab. 4/5 10 20 25 12 22 25 26 24-38 26-38 27-39 33-42 26-39 31-40 36-42 36-44 Subscription