Multi-grain-size hard alloy and preparation method thereof

Abstract

The invention belongs to the technical field of hard alloy preparation, and particularly relates to a multi-grain-size hard alloy and a preparation method thereof. Certain amounts of Co powder, WC powder, amorphous alloy powder and a forming agent are weighed according to a target alloy component ratio and are uniformly mixed, and a novel hard alloy containing a micron-submicron-nano multi-scale structure is prepared through a pre-sintering and densification sintering two-step method multi-physics field coupling rapid sintering technology. According to the method, presintering is superplastic hot pressing sintering, primary bonding is achieved through superplasticity of the amorphous alloy in a supercooled liquid phase region, the amorphous alloy serves as a bonding phase, the densification sintering time is shortened, and WC grain growth is avoided; densification sintering is liquid phase sintering with Co serving as a binding phase, so that the raw material powder is further bound, W-rich nanocrystals are separated out through crystallization of the amorphous alloy, beneficial elements or compounds of the beneficial elements are introduced, the multi-grain-size hard alloy is formed, and the comprehensive performance of the hard alloy is improved.

Description

technical field [0001] The invention belongs to the technical field of hard alloy preparation, and more specifically relates to a multi-grain scale hard alloy and a preparation method thereof. Background technique [0002] Cemented carbide is a cermet material with high hardness and high wear resistance. It is known as "the tooth of industry" and has become an indispensable key material for the development of modern industrial society. It is widely used in the automotive industry, aerospace, integration Various fields such as circuit manufacturing. However, cemented carbide also presents both opportunities and challenges, and cemented carbide mainly uses Co as the binder phase. Co as a strategic resource, due to the widespread use of lithium batteries, the consumption of Co has been exacerbated, and my country has gradually become the largest producer and major consumer of refined Co in the world. 1%, long-term dependence on imports, which also makes hard alloys expensive a...

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Problems solved by technology

[0003] But, these methods face some problems simultaneously: (1) the patent No. is the invention patent of CN 111254336 A, after adding NiCl 2 ·6H 2 When O is used as a sintering aid instead of Co to prepare WC-Ni cemented carbide, the heating temperature is as high as 1400°C-2000°C and the heating time is 30min-200min, which seriously aggravates the grain coarsening of WC. In addition, the solubility of WC in Ni is high. , it is easy to cause defects such as pores and nickel pools after sintering of cemented carbide; (2) the addition of rare earths and their compounds will indeed refine the grains: the patent No. is CN 111057928 A invention patent, after adding Y 2 o 3 The WC grains can be refined by dispersion strengthening to improve the performance of the alloy, however, Y 2 o 3 The addition of Co does not reduce the amount of Co used, and at the same time reduces thermoplasticity and toughness; the invention patent of CN109468516 A can obviously inhibit the grain growth by adding a small amount of rare earth elements, but it is difficult to ensure uniform dispersion, and it is extremely difficult in the sintering process. Oxidation is easy to occur; (3) The invention patent of CN110438384A prepares an iron-nickel-based ultrafine-grained hard alloy, which can improve the strength and toughness, but for the directly added aluminum powder, it will burn out during the sintering process , it is difficult to guarantee the utilization rate, so we need to consider adding compounds directly to avoid burning loss; (4) Adding transition metal carbides can inhibit WC grain growth: literature "Bouleghlem M, Zahzouh M, Hamidouche M, etal.Microstructural and Mechanical Investigation of WC-TiC-Co CementedCarbides Obtained by Conventional Powder Metallurgy[J].International Journal of Engineering Research in Africa.2019,45:1-14" pointed out that adding TiC, TaC, NbC will refine WC grains, but relatively , the density of the formed cemented carbide is not particularly high; (5) the invention patent with the patent number of CN 112359241A uses in-situ reaction to generate fine-grained WC powder, and further sinters with coarse-grained WC powder to form twin-crystal heterogeneous cemented carbide, It can reduce the production cost and improve the performance, but the in-situ reaction is difficult to control; (6) the selection of a suitable process will have a certain impact on the cemented carbide, especially the traditional one-step sintering method cannot inhibit the grain growth at the same time Improve the density of the sintered sample

The invention patent with the patent number CN 103667844 A proposes the preparation of cemented carbide with a non-uniform structure of thickness and thickness. However, it can improve the strength and toughness of the alloy to a certain extent by blending and sintering WC powder with different particle sizes and other powder materials. The preparation cost of fine WC is high. In addition, during the sintering process, coarse and fine WC powders tend to aggregate and grow unevenly, especially if nano-grains are added for co-sintering, nano-grains are prone to agglomeration, and the agglomerated grains It may also affect the properties of the alloy

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