CN107866754A - A kind of porous cubic boron nitride abrasive wheel working lining based on graphene combined binder and preparation method thereof - Google Patents

Abstract

A porous cubic boron nitride grinding wheel working layer based on graphene composite binder and its preparation method, the grinding wheel working layer is composed of Cu-Sn-Ti composite solder (10%Ti, 72%Cu, 18%Sn), graphite Graphene particles, ammonium bicarbonate particles, cubic boron nitride abrasive particles, the preparation method is: 55wt%-65wt% Cu-Sn-Ti composite solder and 5wt% graphene particles, after adding butyral colloidal solution Mix evenly, and obtain graphene composite binder after drying, ball milling, and sieving; mechanically mix graphene composite binder with ammonium bicarbonate particles and cubic boron nitride abrasive grains, and cool through the unilateral axial direction of the mold at 200MPa The working layer blank is made by pressing, and the pore-forming agent is removed to make the working layer blank of the porous grinding wheel; then the working layer of the porous cubic boron nitride grinding wheel is formed by vacuum liquid phase sintering. The prepared open-pore cubic boron nitride grinding wheel working layer has the characteristics of high porosity, high strength, good water permeability and good thermal conductivity.

Description

A porous cubic boron nitride grinding wheel working layer based on graphene composite binder and its preparation method

technical field

The invention belongs to the technical field of superabrasive tools, in particular to a method for preparing an open-pored cubic boron nitride (Cubic Boron Nitride, CBN) grinding wheel working layer based on a graphene composite binder.

Background technique

With the wide application of difficult-to-machine materials such as nickel-based superalloys and titanium alloys in aerospace manufacturing, cubic boron nitride (Cubic Boron Nitride, CBN) grinding wheels are widely used as a superhard abrasive Grinding of processed materials. In order to adapt to the working conditions of fast grinding wheel wear, large grinding load and high grinding temperature in the grinding process of difficult-to-machine materials represented by nickel-based superalloys, in theory, the abrasive layer of CBN grinding wheel needs to have high abrasive grain holding force. , sharp cutting edge, and good surface stability, it must also meet the requirements of high strength and high porosity.

At this stage, the CBN grinding wheels used for grinding difficult-to-machine materials at home and abroad are divided according to the type of binder used, mainly including resin bond CBN grinding wheels, vitrified bond CBN grinding wheels and metal bond CBN grinding wheels (including sintered type) Metal bond CBN grinding wheel, electroplated metal bond CBN grinding wheel and the current development of single-layer brazing metal bond CBN grinding wheel). From the perspective of the bond strength between the bond and the CBN abrasive grains, resin bond CBN grinding wheels mainly use phenolic resin materials with high elasticity and poor heat resistance as the bond, so the abrasive grains have weak holding force and are easy to fall off, which is not suitable for heavy-duty high-efficiency grinding. processing. The ceramic bonded CBN grinding wheel has holes, so that the cutting fluid can effectively enter the grinding arc area, and has a large space for chips. It is not easy to heat and block during the grinding process, and the self-sharpening of the grinding wheel is very good. However, the sintering temperature of the vitrified bond CBN grinding wheel is high, and its strength and impact resistance are low. Moreover, the vitrified bond CBN grinding wheel is sharpened by the continuous wear of the bond during the grinding process, and the service life of the grinding wheel is limited. The sintered metal bond CBN grinding wheel usually uses bronze, iron and nickel alloy as the main bond. The abrasive holding strength is relatively high, the temperature resistance and thermal conductivity are good, the service life is long, the shape retention is good, and it can bear a large load. . However, the traditional metal-bonded CBN sintered grinding wheels are all dense. In order to pursue high holding force on abrasives in their manufacture, their density is generally used as an important indicator to measure the quality of the grinding wheel, resulting in poor self-sharpening of the grinding wheel, easy clogging, Difficult to reshape and sharpen initially and after wear.

In view of this, in order to further improve the grinding performance of metal bond CBN grinding wheels when processing high-strength, tough and difficult-to-machine materials, the requirement to ensure that the abrasive layer of the grinding wheel has both high porosity and high strength is still an urgent need to be solved in the development of porous metal bond CBN grinding wheels. key issues.

Contents of the invention

For the problems existing in the prior art, the object of the present invention is to propose a porous cubic boron nitride grinding wheel working layer based on a graphene composite binder and a preparation method thereof, which can improve the strength and porosity of the metal bond CBN grinding wheel, and the obtained The grinding wheel can realize efficient and precise grinding of difficult-to-machine materials represented by nickel-based superalloys.

To achieve the above object, the present invention adopts the following technical solutions:

A porous cubic boron nitride grinding wheel working layer based on graphene composite binder, which is uniformly mixed with Cu-Sn-Ti composite solder, graphene particles, sodium bicarbonate particles and CBN abrasive particles, pressurized and heated Holes, vacuum liquid phase sintering and other operating steps to finally produce a porous CBN grinding wheel working layer.

Further, the raw material components and mass percentage content of the working layer of the open-pore cubic boron nitride grinding wheel are: 15%-20% CBN (cubic boron nitride) abrasive grains, 5% graphene particles, 15%- 20% ammonium bicarbonate particles, 55%-65% Cu-Sn-Ti composite solder;

Further, the mass percentage content of each component of the raw material of the Cu-Sn-Ti composite solder is: 10% Ti, 72% Cu, 18% Sn.

Further, the CBN abrasive particle size is 150-180 microns;

Graphene particles adopt multi-layer graphene (number of layers <10), particle size is 3-6 microns;

Ammonium bicarbonate particles are irregular in shape, with an equivalent diameter of 200-400 microns;

The particle size of the Cu-Sn-Ti composite solder particles is 20-30 microns.

The preparation method of the porous cubic boron nitride grinding wheel working layer based on graphene composite binder, at first, in Cu-Sn-Ti composite solder, uniformly mixes graphene particle and makes graphene composite binder, and pore-forming agent bicarbonate Ammonium and C BN abrasive grains are added to the graphene composite binder, mixed thoroughly, and then pressurized, dried to remove the pore-forming agent, and vacuum liquid-phase sintering to finally obtain open pores with high porosity and high strength. CBN grinding wheel working layer, and enhance the water permeability and thermal conductivity of the grinding wheel working layer to a certain extent.

Specifically, the following steps are included:

(1) Graphene and Cu-Sn-Ti composite solder are mixed evenly, and the concentration that is prepared in advance is 5wt.% butyral colloidal solution that is dripped into, after mixing evenly, dry, ball mill, sieve, make graphene composite binder;

(2) Add CBN abrasive grains and pore-forming agent ammonium bicarbonate particles to the graphene composite binder, mix evenly, pack into a cold-press mold, and finally make a working layer segment blank;

(3) baking the obtained working layer segment blank to remove the pore-forming agent ammonium bicarbonate, and making the porous grinding wheel working layer blank;

(4) Place the prepared porous grinding wheel working layer blank in a vacuum furnace and heat up to 880°C for vacuum liquid phase sintering. The temperature rise and fall curves are: from room temperature to 150°C in 10 minutes, and keep warm for 10 minutes; then heat up to 150°C in 45 minutes. 600°C, keep warm for 20 minutes; then raise the temperature to 880°C for 56 minutes, keep warm for 30 minutes; then cool to room temperature with the furnace and leave the furnace to prepare the CBN grinding wheel working layer nodes. It has the characteristics of high open porosity, high strength and good thermal conductivity.

The beneficial effects of the present invention are:

The invention mixes graphene particles evenly into Cu-Sn-Ti composite solder to prepare graphene composite binder, and the graphene composite binder and CBN abrasive particles react chemically in the vacuum liquid phase sintering process, improving the metal binder The wettability of CBN improves the holding strength of abrasive grains while maintaining the characteristics of super wear resistance and sharp cutting edge of CBN abrasive grains.

Description of drawings

Figure 1 is a schematic diagram of the organizational structure of the working layer of the CBN grinding wheel;

Figure 2 is a physical map of the large pores in the working layer of the CBN grinding wheel;

Fig. 3 is a physical diagram of the organizational structure of the working layer of the CBN grinding wheel prepared by the present invention.

In Figure 1: 1-CBN abrasive grains; 2-Cu-Sn-Ti active matrix alloy; 3-macropores; 4-micropores; 5-grinding wheel substrate

Detailed ways:

Example 1

The working layer of the porous cubic boron nitride grinding wheel is composed of Cu-Sn-Ti composite solder, graphene particles, sodium bicarbonate particles and CBN abrasive particles 1 according to uniform mixing, pressure molding, heating pore making, vacuum liquid phase sintering and other operations The steps are finally made.

The equivalent particle size of the irregular ammonium bicarbonate particles is 200-400 microns, and its mass percentage of the whole working layer is 15%.

The mass percent of Cu-Sn-Ti active matrix alloy 2 is selected to be 65% (the content of Ti is 10%, the content of Cu and Sn alloy is 90%, and the ratio is 4:1), and the particle size is 20-30 microns.

The graphene particles adopt multi-layer graphene (number of layers<10), the particle size is 3-6 microns, and the mass percentage is 5%.

The particle diameter of CBN abrasive grain 1 is 150-180 microns, and the mass percentage is 15%.

The preparation method is:

(1) Mix graphene and Cu-Sn-Ti composite solder evenly, and drop into 1ml of butyral colloidal solution, after stirring fully, put it into a constant temperature blower box and bake at 60°C for 30 minutes, and the mixture is Fully ball milling and sieving to obtain a graphene composite binder;

(2) Mix the graphene composite binder, ammonium bicarbonate particles and CBN abrasive particles uniformly by mechanical stirring, and make the above-mentioned uniform mixture into a working layer blank by 200MPa unilateral axial pressure;

(3) Place the working layer blank in a constant temperature blower box and bake at 100°C for 120 minutes to remove the pore-forming agent ammonium bicarbonate to prepare a porous working layer blank;

(4) Heat the porous working layer blank to 880°C at high temperature in vacuum and keep it warm for 30 minutes. Through sufficient liquid phase sintering, the Cu-Sn-Ti composite solder, CBN abrasive grains and graphene particles undergo chemical reactions, and wait to be cooled to Remove from oven at room temperature. The heating and cooling curve is as follows: 10 minutes from room temperature to 150°C, heat preservation for 10 minutes; then 45 minutes to 600°C, heat preservation for 20 minutes; then 56 minutes to 880°C, heat preservation for 30 minutes.

Fig. 1 shows the schematic diagram of abrasive grains and pore arrangement of the CBN grinding wheel working layer prepared in Example 1 of the invention. It is not difficult to see that the porosity prepared by ammonium bicarbonate particles can reach 60%, and the shape of the pores is irregular, and the pore diameter is remarkable. It is larger than the internal pore structure of the metal bond grinding wheel; its bending strength exceeds 80MPa measured by the three-point bending test, which meets the requirements of high porosity and high strength of the working layer of the grinding wheel. In addition, during the fracture process of the bending test of the working layer segment, no abrasive particle shedding was found on the cross section, which proves that the bond layer provides a high holding force for the abrasive particle while maintaining the sharp cutting edge and super wear resistance of the abrasive particle.

The process parameter that embodiment 1-4 adopts is different from embodiment 1 as shown in table 1, and all the other unlisted contents are with embodiment 1:

Table 1

In the case that the graphene addition amount is 5wt.%, and the mass fraction of CBN abrasive grains is 15wt.%, ammonium bicarbonate particles are added to prepare a nodal sample with a concentration of 100%, and the bending strength of ammonium bicarbonate particles is experimentally studied and the effect of open porosity. The results show that the higher the content of ammonium bicarbonate particles, the lower the block strength and the larger the open porosity. The content of ammonium bicarbonate particles increased from 15wt.% to 20wt.%, and the block strength decreased from 83.2MPa to 42.6MPa. The open porosity increased from 61.2 to 76.2 vol.%.

When the ammonium bicarbonate particles were fixed at 15%-20%, the influence of the mass fraction of CBN abrasive grains on the performance was investigated, and it was found that the bending strength of the segment and the open porosity remained basically unchanged with the increase of the mass fraction of CBN abrasive grains.

Graphene particles act as a skeleton phase in the nodule, and when the amount of graphene added is less than 5wt.%, the nodule cannot maintain the shape before brazing and collapses. When it is higher than 5%, the bending strength of the nodule sample Significantly reduced, aggravating the wear of the grinding wheel.

Claims (5)

1. A porous cubic boron nitride grinding wheel working layer based on a graphene composite binder, characterized in that its raw material components and mass percentage content are: 15%-20% CBN abrasive grains, 5% graphene particles , 15%-20% ammonium bicarbonate particles, 55%-65% Cu-Sn-Ti composite solder. 2. the porous cubic boron nitride grinding wheel working layer based on graphene composite binder according to claim 1, is characterized in that: the mass percent content of each component of the raw material of Cu-Sn-Ti composite solder is: 10%Ti , 72% Cu, 18% Sn. 3. the porous cubic boron nitride grinding wheel working layer based on graphene composite binder according to claim 1, is characterized in that: The particle size of the CBN abrasive grains is 150-180 microns; Graphene particles adopt multi-layer graphene, and the particle size is 3-6 microns; Ammonium bicarbonate particles are irregular in shape, with an equivalent diameter of 200-400 microns; The particle size of the Cu-Sn-Ti composite solder particles is 20-30 microns. 4. The porous cubic boron nitride grinding wheel working layer based on graphene composite binder according to claim 1, characterized in that: the number of layers of graphene particles<10. 5. the preparation method of the porous cubic boron nitride grinding wheel working layer based on graphene composite binder according to claim 1, is characterized in that, comprises the following steps: Step (1), mix graphene and Cu-Sn-Ti composite solder evenly, drop into butyral colloidal solution, mix evenly, dry, ball mill, and sieve to prepare graphene composite binder; Step (2), adding CBN abrasive grains and pore-forming agent ammonium bicarbonate particles to the graphene composite binder, mixing evenly, and putting them into a cold-press mold to make a working layer block blank; Step (3), baking the prepared working layer segment blank to remove the pore-forming agent ammonium bicarbonate to prepare a porous grinding wheel working layer blank; Step (4), put the prepared porous grinding wheel working layer blank in a vacuum furnace and heat up to 880°C for vacuum liquid phase sintering. The temperature rise and fall curves are: 10 minutes from room temperature to 150°C, heat preservation for 10 minutes; then 45 minutes Raise the temperature to 600°C and keep it warm for 20 minutes; then raise the temperature to 880°C for 56 minutes and keep it warm for 30 minutes; then cool down to room temperature with the furnace and leave the furnace to prepare the CBN grinding wheel working layer nodes.