A boron-containing gradient cemented carbide with a shell structure and its preparation method

Abstract

The invention discloses a boron-containing gradient cemented carbide with a shell structure and a preparation method thereof. The method is to perform boronizing heat treatment on a sintered dense cemented carbide matrix in a boron-containing filler, and the temperature of the heat treatment is slightly lower than that of the hard alloy. The liquidus point of the alloy matrix. The boron-containing gradient cemented carbide has a three-layer structure of surface layer, subsurface layer and core; the surface layer is a shell structure with a uniform distribution of boron-containing phases, the subsurface layer is a gradient transition structure with uniform changes in boron-containing phases, and the core is a structure that does not contain Boron-containing cemented carbide structure; and the concentration of boron-containing phase gradually decreases from the interface between the surface layer and the subsurface layer inwards, and completely disappears at the interface between the subsurface layer and the core. The service performance of the boron-containing gradient cemented carbide is obviously higher than that of ordinary cemented carbide, and the existence of the gradient layer avoids sudden failure caused by the performance difference between the boronizing shell layer and the alloy matrix.

Description

technical field [0001] The invention relates to the technical field of hard alloy material manufacture, in particular to a boron-containing gradient hard alloy with a shell structure and a preparation method thereof. Background technique [0002] Cemented carbide is widely used in metal processing, engineering machinery, mold manufacturing and other fields. With the continuous upgrading of the manufacturing industry, the service conditions of cemented carbide have become increasingly stringent, and various cemented carbide strengthening technologies have continued to develop. Among them, the method of introducing B, C, N and other elements and their compounds (especially compounds with IVB, VB, VIB group metals) into the cemented carbide can effectively improve the mechanical properties of the cemented carbide because it can have a gradient distribution. The hardness and wear resistance of high-quality alloys have been widely used. [0003] Boride has extremely high meltin...

AI Technical Summary

Problems solved by technology

At present, the representative methods of cemented carbide boronizing include: 1. "Cemented Carbide Surface Boronizing Treatment Method", Patent No. Publication No. CN101948997B; in this method, cemented carbide is placed in a solid composed of boron donor, activator and filler. In the boronizing agent, a dense boronizing layer of tens to hundreds of microns can be formed on the surface of the cemented carbide after the temperature is raised to 800-1300°C under negative pressure and kept for 0.5-8 hours; the disadvantage of this method is: boronizing layer Too thin, less than 1 mm. Under actual service conditions, such as cemented carbide buttons for geological and mining drill bits, the actual wear thickness of the alloy usually exceeds 1 mm; in addition, due to the thin boronizing layer, the gap between the boronizing layer and the substrate The transition area of ​​the cemented carbide is also narrow, resulting in a sudden change in performance from the boronizing layer to the substrate, which is prone to stress concentration and damage during use, which is not conducive to the extension of the service life of the cemented carbide

2. "Cemented Carbide Treated with Boron", Patent No. Publication No. CN1039837C; This method provides a boronizing method, placing cemented carbide in alumina fillers containing BN and C, in hydrogen or nitrogen or In the mixed atmosphere of the two, the temperature is raised to above 1400°C for 70 minutes, and a boronizing layer with a depth of more than 3mm can be obtained with a dispersed boron-containing phase; The number of boron-containing phases from the surface to the interior is continuously decreasing, resulting in a rapid decline in the performance of the alloy in the later period of service; at the same time, the amount of boron-containing phases on the surface layer of this method is less than that of the first method, and the strengthening effect is also weak.

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