Method for preparing gradient cemented carbide with cubic carbide free layer

Abstract

The invention relates to a process for preparing gradient cemented carbide with a cubic carbide free layer, which is generally used for preparing a coated cemented carbide substrate. The process is characterized in that: an initial component adopts a nitrogen-free cemented carbide raw material, and is prepared into a blade or a sample green compact by a standard cemented carbide preparation process; and a sintering process adopts a one-step sintering method comprising the following steps of: performing sintering by adopting normal dewaxing and deoxidizing processes, introducing micro-pressure nitrogen to react the nitrogen with carbides in the cemented carbide substrate to synthesize a nitrogen-containing cubic phase, evacuating the nitrogen at gradient sintering temperature and switching to sintering in a denitriding atmosphere like vacuum to form a surface layer into a cubic phase-free and cobalt layer-rich structure, namely, the cubic carbide free layer. The process is characterized in that: a nitrogen-containing phase is not added into the cemented carbide raw material, so the increasing of alloy porosity caused by the early decomposition of the nitrogen-containing phase can be avoided; the reaction nitrogen-addition of the cemented carbide substrate is realized by controlling the reaction between the sintering atmosphere and the cemented carbide substrate, so the gradient cemented carbide with the cubic carbide free layer also can be prepared under the condition of not adding the nitrogen-containing phase into the initial component; due to the adoption of the one-step sintering method, the sintering process can be simplified and the production cost can be reduced; and the prepared gradient cemented carbide comprises the cubic carbide free layer with the thickness of 10 to 40 microns, and has high compactness and bending resistance.

Description

technical field [0001] The invention relates to a preparation process of a beta layer-removed gradient cemented carbide. Background technique [0002] Cemented carbide has been widely used in the field of metal cutting because of its high strength, high hardness, wear resistance, corrosion resistance and other advantages. In recent years, the development of modern manufacturing industry has put forward higher and higher requirements on the performance of cemented carbide cutting tools. Good impact resistance, cemented carbide with traditional homogeneous structure usually cannot meet this requirement. For this reason, one or more layers of wear-resistant coatings, such as TiN, Ti(C,N), Al 2 o 3 Wait. Since the deposition temperature of general CVD technology may be as high as 800-1000 ° C, and there is a difference in thermal expansion coefficient between the coating and the substrate, a large thermal stress will inevitably be generated at the interface between the coati...

AI Technical Summary

Problems solved by technology

[0008] 2) When adding TiC with lower nitrogen content 0.5 N 0.5 , TiC 0.7 N 0.3 When the powder is prepared, one-step sintering method can be used, but at this time the activity of nitrogen in the matrix is ​​too low, and it is not easy to form a gradient cemented carbide with the ideal thickness of the beta-free layer at the same sintering temperature. Therefore, it is necessary to increase the nitrogen content of the matrix. Activity, if the method of increasing the sintering temperature is used, it will be limited by the process and equipment; if the method of reducing the particle size of Ti(C,N) powder is used, additional powder processing technology is required, and the production process and cost are also increased

Images