阅读说明：本技术 一种梯度纳米复合金属陶瓷刀具材料及其烧结工艺 (Gradient nano composite metal ceramic cutter material and sintering process thereof ) 是由 倪秀英 赵军 孙军龙 于 2018-08-15 设计创作，主要内容包括：本发明属于陶瓷材料技术领域,涉及一种具有梯度结构的纳米复合金属陶瓷刀具材料及其烧结工艺。该刀具材料具有五层对称梯度层次结构,相对于中心层对称的层中组分含量相同,相对中心层对称的层的厚度也相同,梯度层厚度按第一层厚度/第二层厚度=第二层厚度/第三层厚度=0.2确定。其制备方法包括步骤:(1)按每层各组分的含量配料；(2)对各层中纳米颗粒进行分散；(3)将各层中其它材料与分散的纳米材料混料；(4)采用分层铺填粉末形成梯度结构,在真空环境中采用二阶段烧结工艺烧结。本烧结工艺利用了颗粒界面迁移动力和扩散动力的差异,使材料致密度提高,而且颗粒没有异常长大。烧结样品中Ni,Mo的梯度分布,使得刀具材料的力学性能呈梯度阶梯变化,保证了梯度材料表层高硬度,高抗氧化性,内层韧性、强度较好的要求。(The invention belongs to the technical field of ceramic materials, and relates to a nano composite metal ceramic cutter material with a gradient structure and a sintering process thereof. The cutter material has a five-layer symmetrical gradient hierarchical structure, the components in the layers symmetrical relative to the central layer have the same content, the thicknesses of the layers symmetrical relative to the central layer are also the same, and the thicknesses of the gradient layers are determined according to the thickness of a first layer/the thickness of a second layer = the thickness of the second layer/the thickness of a third layer = 0.2. The preparation method comprises (1) mixing materials according to the content of each layer of components; (2) dispersing the nanoparticles in each layer; (3) mixing other materials in each layer with the dispersed nano materials; (4) adopts layered filling powder to form a gradient structure, and adopts a two-stage sintering process to sinter in a vacuum environment. The sintering process utilizes the difference between the migration power and the diffusion power of the grain interface, so that the density of the material is improved, and the grains do not grow abnormally. The mechanical properties of the tool material are in gradient step change due to the gradient distribution of Ni and Mo in the sintered sample, and the requirements of high hardness, high oxidation resistance, and better toughness and strength of the inner layer of the gradient material are met.)

1. A gradient nano-composite cermet cutting tool material has a symmetrical gradient structure with 5 layers, and the symmetrical layers with same component content and symmetrically distributed thickness, wherein Al in each layer₂O₃Is nano Al₂O₃And micron Al₂O₃Mixed, nano-Al₂O₃The volume content of (a) is fixed to 11%; the thickness of the five-layer gradient layer is determined according to the thickness of the first layer/the thickness of the second layer-the thickness of the second layer/the thickness of the third layer = 0.2; the first and fifth gradient layers contain nano metal phases, and the other gradient layers contain micron metal phases; the first layer and the fifth layer each contain 54.25 vol.% Al₂O₃45% of micron (W, Ti) C, 0.5% of nano Ni and 0.25% of nano Mo; the second layer and the fourth layer each contain 47.5% by volume of Al₂O₃47% of micro (W, Ti) C, 2.5% of micro TiN, 2% of micro Ni, 1% of micro Mo; the third layer comprises 32.5-14% by volume of Al₂O₃48% -53% of micron (W, Ti) C, 4% -10% of micron TiN and 3% -8% of micron TiNNi, 1.5% -4% of micron Mo; the micro MgO and the micro NiO respectively account for 0.5 percent of the total mass of each layer of powder.

2. The gradient nanocomposite ceramic tool material of claim 1, having five gradient layer thicknesses determined by first layer thickness/second layer thickness-second layer thickness/third layer thickness = 0.2; the first and fifth gradient layers do not contain metal phase, and the rest gradient layers contain metal phase.

3. The method for preparing a gradient nano composite cermet cutting tool material as claimed in claim 1 or 2, wherein: the method comprises the following steps:

(1) preparing materials: the first layer and the fifth layer each contain 54.25 vol.% Al₂O₃45% of micron (W, Ti) C, 0.5% of nano Ni and 0.25% of nano Mo; the second layer and the fourth layer each contain 47.5% by volume of Al₂O₃47% of micro (W, Ti) C, 2.5% of micro TiN, 2% of micro Ni, 1% of micro Mo; the third layer comprises 32.5-14% by volume of Al₂O₃48% -53% of micron (W, Ti) C, 4% -10% of micron TiN, 3% -8% of micron Ni, 1.5% -4% of micron Mo, micron MgO and micron NiO, wherein the micron MgO and the micron NiO respectively account for 0.5% of the total mass of each layer of powder; (2) dispersing and mixing the nano particles in each layer: nano Al₂O₃The dispersion of the Al-based nano-material takes absolute ethyl alcohol as a dispersion medium, and relative nano-Al is added₂O₃1% by mass of nano Al₂O₃The special dispersant of (2) to prepare a suspension of the nano material; mixing the micron powder particles taken from the same layer with the suspension of the nano material well dispersed in the layer, ball-milling for 48 hours on a planetary ball mill, and then carrying out vacuum drying and sieving to obtain well-dispersed composite metal ceramic material powder; (3) loading and sintering: loading materials by adopting a powder layering and paving method, sintering the composite powder material in a vacuum environment by adopting a two-stage hot pressing sintering process, heating from room temperature to 1200 ℃, wherein the heating speed is 20 ℃/min, and the pressure is increased to 5 MPa; when the temperature is from 1200 ℃ to 1700 ℃, the heating rate is unchanged, the pressure is stably and uniformly increased to 30MPa, and the temperature is kept for 3min to obtain the materialObtaining a certain sintering driving force; then reducing the temperature to 1450 ℃, reducing the temperature at the speed of 50 ℃/min, continuously preserving heat and pressure for 60min, keeping the pressure at 30MPa, and then cooling along with the furnace.

4. The sintering process of the gradient nano-composite metal ceramic cutter material according to claim 3, comprising heating, first-stage heat preservation, cooling and second-stage heat preservation, and is characterized in that:

the temperature rising step: the temperature rising speed is 20 ℃/min, the pressure is increased to 5MPa, and the gas in the powder is discharged; the first stage heat preservation step: the sintering temperature of 1600-1725 ℃, preferably 1700 ℃, and the heat preservation time of 3min in the first stage ensure that the powder is uniformly heated and a certain sintering driving force is obtained; and the second stage heat preservation step: the sintering temperature of the second stage is 1400-1500 ℃, preferably 1450 ℃, the cooling speed is 50 ℃/min, and the heat preservation time of the second stage is 30-60 min, so that the surface layer and the inner layer are sintered compactly, and crystal grains are not excessively grown.

5. The gradient cermet having a low surface metal content of claim, characterised in that the average (W, Ti) C particle size in the hard phase is not more than 2 μm and the phases are uniformly distributed.

Technical Field

The invention belongs to the technical field of composite ceramic cutter materials, and particularly relates to a gradient nano composite metal ceramic cutter material and a sintering process thereof.

Background

The ceramic cutter material has excellent heat resistance, wear resistance and chemical stability, has incomparable advantages of a hard alloy cutter in the field of high-speed cutting and the aspect of cutting difficult-to-process materials, but has lower strength and fracture toughness, and restricts the use of the ceramic cutter. At present, the domestic and foreign researches adopt various toughening and reinforcing mechanisms to improve the toughness and the strength of the ceramic cutter, but the effect is not very ideal; the bending strength and fracture toughness of the metal ceramic are higher than those of the ceramic, but the high-temperature mechanical properties of the material are poor due to the low melting point of the metal phase. Moreover, the high-speed cutter, especially the intermittent cutting cutter, has different loads on all parts and different required main mechanical property requirements. The gradient Functional material (FGM for short) can realize 'cutting and splicing' of material performance, and gradient changes of components, microstructures and performance are introduced into a member to enable the member to meet different performance requirements of the member on different positions, and finally the member obtains the best comprehensive performance. The gradient functional cermet material opens up a wide prospect for improving the comprehensive mechanical property of the cutter material. Therefore, FGM can meet the requirements of hard surface layer and middle toughness required by interrupted hard cutting processing, and can relieve the requirements of a cutter on thermal stress and impact stress.

The process of making cermet cutting tool materials involves complex thermodynamic and kinetic phenomena, with numerous parameters such as: chemical compositions, sintering temperature, sintering time, sintering atmosphere and the like all have obvious influence on the microstructure and the performance of the ceramic material. To date, a large amount of studies have been made by domestic and foreign scholars on the sintering process of ceramics and cermets without metal phase, and the suitable maximum sintering temperature of the two is generally different by more than 100 ℃. In addition, at high temperatures, the metal phase is easily diffused and homogenized. Meanwhile, the following results are found through retrieval: at present, the difference of sintering processes of two materials is considered, and the preparation of gradient materials with different metal contents in each layer is not researched specially.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a gradient nano composite metal ceramic cutter material which is suitable for hard cutting and has a surface layer containing a small amount of nano metal phase and an inner layer containing micron metal phase by combining high thermal shock resistance of a gradient functional material, and also provides a sintering process of the cutter material which has the advantages of low production cost, simple process, capability of inhibiting excessive growth of particles and diffusion of the metal phase and compactness. Aims to keep the advantages of higher hardness, oxidation resistance and the like of the gradient metal ceramic cutter material and improve the comprehensive mechanical properties, particularly the bending strength and the fracture toughness of the inner layer of the gradient material.

The invention is realized by the following mode

The gradient nano composite metal ceramic cutter material has a symmetrical gradient structure, the number of layers is 5, the components in the layers symmetrical relative to the central layer have the same content, the thicknesses are symmetrically distributed, and Al of each layer is₂O₃Is nano Al₂O₃And micron Al₂O₃Mixed, nano-Al₂O₃The volume content of (b) was fixed to 11%. The thickness of the five-layer gradient layer is determined according to the thickness of the first layer/the thickness of the second layer = the thickness of the second layer/the thickness of the third layer = 0.2; the first and fifth gradient layers contain nano metal phase, and the rest gradient layers contain micron metal phase. The first layer and the fifth layer each contain 54.25 vol.% Al₂O₃45% of micron (W, Ti) C, 0.5% of micron Ni, 0.25% of micron Mo; the second layer and the fourth layer each contain 47.5% by volume of Al₂O₃47% of micro (W, Ti) C, 2.5% of micro TiN, 2% of micro Ni, 1% of micro Mo; the third layer comprises 36-25% of Al by volume percent₂O₃50% -53% of micron (W, Ti) C, 6.5% -10% of micron TiN, 5% -8% of micron Ni and 2.5% -4% of micron Mo.

The preparation and sintering process of the gradient nano composite ceramic cutter material comprises the following steps: (1) batching: the components of each layer are mixed according to the volume ratio of the components given below, and the components of the first layer and the fifth layer are 54.25 percent of Al according to volume percentage₂O₃45% of micron (W, Ti) C, 0.5% of micron Ni, 0.25% of micron Mo; the second layer and the fourth layer each contain 47.5% by volume of Al₂O₃47% of micro (W, Ti) C, 2.5% of micro TiN, 2% of micro Ni, 1% of micro Mo; the third layer comprises 36-25% of Al by volume percent₂O₃50% -53% of micron (W, Ti) C, 6.5% -10% of micron TiN, 5% -8% of micron Ni and 2.5% -4%% of micron Mo. The micro MgO and the micro NiO respectively account for 0.5 percent of the total mass of each layer of powder.

(2) Dispersing and mixing the nano particles in each layer: nano Al₂O₃The dispersion of the Al-based nano-material takes absolute ethyl alcohol as a dispersion medium, and relative nano-Al is added₂O₃1% by mass of nano Al₂O₃The special dispersant of (2) to prepare a suspension of the nano material; and mixing the micron powder particles taken from the same layer with the suspension of the nano material well dispersed in the layer, ball-milling for 48 hours on a planetary ball mill, and then carrying out vacuum drying and sieving to obtain the composite cermet material powder material well dispersed.

(3) And (3) sintering: loading materials by adopting a powder layering and paving method, sintering the composite powder in a vacuum environment by adopting a two-stage hot-pressing sintering process, heating from room temperature to 1200 ℃, wherein the heating speed is 20 ℃/min, and the pressure is pre-increased to 5 MPa; then heating to the highest sintering temperature, wherein the heating rate is unchanged, and the pressure is stably and uniformly increased to 30 MPa; keeping the temperature for 3min, then reducing the temperature to 1450 ℃, reducing the temperature rate to 50 ℃/min, keeping the temperature and the pressure for 60min, keeping the pressure at 30MPa, and then cooling along with the furnace.

In the sintering process, the highest sintering temperature in the first stage is controlled to be 1600-1725 ℃, and the highest sintering temperature is preferably 1700 ℃. The maximum sintering temperature refers to the temperature maintained in the first stage after sintering temperature rise.

In the sintering process, the sintering temperature is controlled to be 1450-1550 ℃ in the second sintering stage, the ceramic particle interface has certain diffusion but does not migrate, and the particles do not grow up. The metal is in liquid phase, and the liquid phase sintering is ensured. The second stage heat preservation time is 30-90 min, preferably 60 min. The densification, the particle growth and the metal loss of the material are well balanced, so that the gradient composite metal ceramic material has the optimal mechanical property.

Compared with the traditional sintering technology, in the sintering process, the sintering process is carried out in two stages, the temperature is raised to a higher temperature in the first stage, and the temperature is kept for a short time, so that the material obtains a certain sintering driving force; then quickly cooling to a lower sintering temperature, preserving heat for a longer time, promoting the material to be compact, avoiding excessive growth of particles, and obtaining the composite material with uniform compact fine particles.

The invention has the beneficial effects that:

the two-stage hot-pressing sintering process is adopted, and the difference between the densification rate of a sintered sample and the growth rate of crystal grains is utilized to inhibit the excessive growth of the crystal grains, so that the effect of refining the crystal grains is achieved. The temperature is kept at a lower temperature, the large-range diffusion of metal at high temperature and high pressure is avoided, and the designed gradient structure with low metal content on the surface layer and high metal content on the inner layer is ensured.

Through the steps, the gradient nano composite metal ceramic cutter material with uniform particle size distribution, almost maintained initial particle size, high bending strength, good fracture toughness and high surface hardness can be prepared.

Drawings

FIG. 1 is a schematic structural view of the gradient nanocomposite cermet cutting tool material of the present invention.

FIG. 2 is a composition distribution diagram of a two-gradient nanocomposite cermet cutting tool material according to an embodiment of the present invention.

Detailed Description

As shown in the figure, the gradient nano composite metal ceramic cutter material has a symmetrical gradient structure, the number of layers is 5, the components in the layers symmetrical relative to the central layer have the same content, the thicknesses are symmetrically distributed, and Al of each layer is₂O₃Is nano Al₂O₃And micron Al₂O₃Mixed, nano-Al₂O₃The volume content of (b) was fixed to 11%. The thickness of the five-layer gradient layer is determined according to the thickness of the first layer/the thickness of the second layer = the thickness of the second layer/the thickness of the third layer = 0.2; the first and fifth gradient layers contain nano metal phase, and the rest gradient layers contain micron metal phase. The first layer and the fifth layer each contain 54.25 vol.% Al₂O₃45% of micron (W, Ti) C, 0.5% of micron Ni, 0.25% of micron Mo; the second layer and the fourth layer each contain 47.5% by volume of Al₂O₃47% of micro (W, Ti) C, 2.5% of micro TiN, 2% of micro Ni, 1% of micro Mo; the third layer comprises the components in percentage by volumeAl with the ratio of 36-25%₂O₃50% -53% of micron (W, Ti) C, 6.5% -10% of micron TiN, 5% -8% of micron Ni and 2.5% -4% of micron Mo. The micro MgO and the micro NiO respectively account for 0.5 percent of the total mass of each layer of powder.

The following examples illustrate the preparation of the gradient nanocomposite ceramic cutting tool material of the present invention.