CN115652127B - Nearly equiaxial grain Mo 2 FeB 2 Preparation method of base metal ceramic - Google Patents
Nearly equiaxial grain Mo 2 FeB 2 Preparation method of base metal ceramic Download PDFInfo
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Abstract
The invention discloses a near equiaxial grain Mo 2 FeB 2 A preparation method of base metal ceramic. The disclosed method comprises the steps of sequentially ball milling, drying and compression molding mixed powder of Mo, feB and Fe to prepare a green body, and then sintering the green body, wherein the sintering process comprises the following steps: the temperature rising rate from room temperature to sintering temperature I is 5-15 ℃/min, the sintering temperature I is 1100-1150 ℃, the heat preservation time I is 10-60 min, the cooling rate from the sintering temperature I to the sintering temperature II is 1-15 ℃/min, the sintering temperature II is 950-1090 ℃, the heat preservation time II is 10-30 h, and then the furnace is cooled. The invention has the advantages of less raw material types and low cost, is beneficial to large-scale and repeated tests and production, and is convenient for industrial application and popularization; by adopting a novel sintering process, the grain directional growth is inhibited, thereby obtaining the approximately equiaxial grain Mo 2 FeB 2 The metal ceramic is an ideal material for preparing tools and dies.
Description
Technical Field
The invention relates to Mo 2 FeB 2 A metal-based ceramic-related art,in particular to a near equiaxial grain Mo 2 FeB 2 A preparation method of base metal ceramic.
Background
The wear-resistant material has extremely wide application in the fields of metallurgy, mine, electric power, building materials, energy, traffic and the like. The field of such materials has changed tremendously over the past few decades. Cermet has been favored by researchers because of its low density, high hardness, good wear resistance, and excellent comprehensive mechanical properties, among which Mo 2 FeB 2 The metal-based ceramic has the advantages of high strength, high hardness, wear resistance, corrosion resistance, high bonding strength with steel and the like, is an ideal material for preparing tools and dies and wear-resistant parts, and is widely used as a cutting tool, a hot extrusion grinding tool of copper, a wire drawing die and the like.
Mo 2 FeB 2 The base metal ceramic is composed of Mo 2 FeB 2 The hard phase and the Fe binding phase are formed, so that the ceramic phase has the advantages of high hardness, high melting point, high chemical stability and the like of the ceramic phase, and the metal binding phase has high strength, high toughness and good processability. Mo prepared at present 2 FeB 2 The base metal ceramic has good mechanical properties, and can basically meet the requirements of conventional service conditions, but researchers hope that the base metal ceramic can be further used for hundred-rod heads, and further improving the performance so as to adapt to more severe working condition environments. In Mo 2 FeB 2 Mo in the base metal ceramic 2 FeB 2 The hard phase occupies about 75% (volume fraction). Therefore, the morphology of the hard phase has an important influence on the mechanical properties of the metal ceramic. Mo (Mo) 2 FeB 2 The growth of the hard phase is directional and takes on a long columnar morphology (a shape factor of about 0.66) when it grows sufficiently. Compared with the nearly equiaxial grains, the long columnar grains can reduce the deformation coordination of the metal ceramic, reduce the deformation of the metal ceramic in the bearing process, and further reduce the strength and toughness of the metal ceramic. Therefore, how to improve Mo was studied 2 FeB 2 The morphology of the crystal grains is approximately equiaxed, so that the improvement of the comprehensive mechanical properties of the crystal grains has important theoretical significance and engineering value. The prior art adopts Cr element doping to reduce Mo 2 FeB 2 The anisotropism of the crystal grain improves the morphology, thereby improving the performance of the crystal grain. However, the doping elements can increase the cost of raw materials, and the components and impurity contents of raw materials produced by different manufacturers in different batches are different, so that the variety of the raw materials is too large to be beneficial to large-scale and repeated tests and production. In addition, the mechanical property of the doped Cr element on the metal ceramic is also limited.
Disclosure of Invention
In order to overcome the defects or shortcomings in the prior art, the invention provides a near equiaxial grain Mo 2 FeB 2 A preparation method of base metal ceramic.
To this end, the method provided by the invention comprises the following steps: ball milling, drying and compression molding are sequentially carried out on mixed powder of Mo, feB and Fe to prepare a green body, and then sintering is carried out on the green body, wherein the sintering process comprises the following steps: the temperature rising rate from room temperature to sintering temperature I is 5-15 ℃/min, the sintering temperature I is 1100-1150 ℃, the heat preservation time I is 10-60 min, the cooling rate from the sintering temperature I to the sintering temperature II is 1-15 ℃/min, the sintering temperature II is 950-1090 ℃, the heat preservation time II is 10-30 h, and then the furnace is cooled.
Optionally, the following components in percentage by mass: 44.0 to 55.0 percent of Mo, 25.0 to 34.0 percent of FeB and 13.0 to 25.0 percent of Fe.
Preferably, the sintering is performed in a vacuum carbon tube furnace.
Preferably, the Mo 2 FeB 2 The shape factor of the crystal grains of the base metal ceramic is 0.72-0.83; the bending strength of the metal ceramic is 1396.8-1812.4 MPa, and the fracture toughness is 13.9-14.6MPa.m 1/2 。
Compared with the prior art, (1) the invention has the advantages of less raw material types and low cost, is beneficial to large-scale and repeated tests and production, and is convenient for industrial application and popularization; (2) by adopting the novel sintering process, not only the densification of the metal ceramic is realized, but also the dissolution-precipitation mechanism of crystal grains is inhibited, and the directional growth degree of the metal ceramic is weakened; finally obtain the Mo with nearly equiaxial grains 2 FeB 2 The metal ceramic is an ideal material for preparing tools and dies.
Drawings
FIG. 1 is Mo in example 1 2 FeB 2 XRD pattern of the base cermet;
FIG. 2 is Mo in example 1 2 FeB 2 A photograph of the microstructure of the base cermet;
FIG. 3 shows Mo in the comparative example 2 FeB 2 Microscopic photograph of the base cermet.
Detailed Description
Unless specifically stated otherwise, scientific and technical terms and methods herein have been understood or implemented by those of ordinary skill in the relevant art based on the knowledge of one of ordinary skill in the relevant art. It should also be understood that the temperature, concentration referred to herein are approximations for purposes of illustration. Although methods and materials similar or equivalent to those described herein can be used in the practice of the present disclosure, some suitable methods and materials are described below. Publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety to the extent that any conflict arises. In addition, the materials, methods, solution concentrations, and examples are illustrative only and are not intended to be limiting. In particular, the person skilled in the art can optimize the material ratios, concentrations, values of the operating parameters, and the order of addition of the reactants involved in the method according to the disclosure of the present invention using conventional experimental periods to achieve the objects of the present invention.
Mo prepared by the prior conventional method 2 FeB 2 The reason that the grains of the base metal ceramic are in a long column shape is mainly because the final sintering temperature is higher in the existing sintering process parameters, so that Mo 2 FeB 2 The dissolution-precipitation mechanism of the hard phase is fully carried out to cause the grain to grow directionally. However, if sintering is performed at a relatively low temperature, the dissolution-precipitation mechanism of the hard phase can be suppressed to decrease the directional growth degree of grains, but the fluidity of the liquid phase is lowered to decrease the density of the cermet. Thus, preparing near equiaxed grain Mo 2 FeB 2 The key difficulty of the base metal ceramic is to reduce the grain growth in a directional mode and simultaneously give consideration to the densification of the metal ceramic. Through hairIntensive studies by the Ming dynasty have found that Mo 2 FeB 2 When the base metal ceramic is sintered, mo is gradually generated along with the temperature rise 2 FeB 2 Solid phase, liquid phase L 1 And liquid phase L 2 . Densification of cermets is predominantly in the liquid phase L 1 The stage is completed by particle rearrangement, at which stage there is also a small amount of grain growth. The grains grow in a directional manner mainly in the liquid phase L 2 Stage through Mo 2 FeB 2 The dissolution-precipitation mechanism of the hard phase proceeds. Thus, it is possible to make use of Mo 2 FeB 2 The microstructure evolution rule of the base metal ceramic during sintering adopts a novel sintering process by improving the sintering process parameters: first, in the liquid phase L 1 And L 2 Preserving heat at a certain temperature for a certain time in a temperature interval, cooling, and mixing with solid phase and liquid phase L 1 And preserving heat at a certain temperature in the temperature interval for a certain time, and then cooling the furnace. The process has the advantages that: densification of the metal ceramic is realized through twice heat preservation, and the two heat preservation temperatures are lower than the liquid phase L 2 Temperature, mo is suppressed 2 FeB 2 The dissolution-precipitation mechanism of the crystal grains reduces the directional growth degree of the crystal grains, and finally the approximately equiaxed crystal grain Mo is obtained 2 FeB 2 And (3) a base metal ceramic.
The purpose of the compression molding is to initially densify the powdery raw material, and the shape and size of the obtained green body depend on the shape of the mold. The molds used in the prior art of ceramics, such as molds with volume dimensions greater than 3mm by 3mm, are suitable for use in the present invention.
The invention is illustrated in further detail by the following examples. The raw materials Mo, feB and Fe powder used in the embodiment of the invention are all commercial chemical pure powder reagents, ball milling is carried out in a planetary ball mill (QM-3 SP 4), then drying is carried out in a rotary evaporator (QE-2000), a stainless steel die is utilized for bidirectional pressing to prepare a blank, and the blank is placed into a vacuum carbon tube furnace (ZT-25) for sintering.
In the present invention, mo was tested using Image Pro Plus, version 6.0 2 FeB 2 The shape factor of the base metal ceramic crystal grain is between 0 and 1, the closer the numerical value is to 1, the more the crystal grain is connectedNearly equiaxed; with reference to national standard GB/T6569-2006, mo is tested by adopting a three-point bending test method 2 FeB 2 Flexural strength of the base cermet specimens; measurement of Mo by Single Edge Notched Beam (SENB) 2 FeB 2 Fracture toughness of the base cermet specimens.
Example 1:
selecting Mo, feB and Fe powder with purity not lower than 99.0% to prepare powder, wherein the powder comprises the following components in percentage by weight: mo:44.0%, feB:31.0%, fe:25.0% mixing; ball milling the mixed powder, drying and compacting to prepare a cylindrical (diameter 44mm, height 8-9 mm) blank; then placing the blank into a vacuum carbon tube furnace for sintering, wherein the specific technological parameters are as follows: the temperature rising rate from room temperature to sintering temperature I is 5 ℃/min, the sintering temperature I is 1100 ℃, the heat preservation time I is 10min, the temperature reducing rate from the sintering temperature I to the sintering temperature II is 1 ℃/min, the sintering temperature II is 950 ℃, the heat preservation time II is 10h, and then the furnace is cooled.
In this embodiment, mo is approximately equiaxed grains 2 FeB 2 The preparation method of the base metal ceramic is simple and the cost is low. The resulting cermet comprises Mo 2 FeB 2 The hard phase and the Fe binding phase (XRD pattern, see figure 1), the microstructure (see figure 2) and the mechanical properties are respectively: the shape factor of the crystal grain is 0.83, the bending strength is 1812.4MPa, and the fracture toughness is 14.6MPa m 1/2 。
Example 2:
selecting Mo, feB and Fe powder with purity not lower than 99.0% to prepare powder, wherein the powder comprises the following components in percentage by weight: mo:49.0%, feB:29.0%, fe:22.0%; ball milling the mixed powder, drying and compacting the mixed powder to prepare a cylindrical (diameter 44mm, height 8-9 mm) blank; then placing the blank into a vacuum carbon tube furnace for sintering, wherein the specific technological parameters are as follows: the temperature rising rate from room temperature to sintering temperature I is 10 ℃/min, the sintering temperature I is 1130 ℃, the heat preservation time I is 30min, the temperature reducing rate from the sintering temperature I to the sintering temperature II is 10 ℃/min, the sintering temperature II is 1000 ℃, the heat preservation time II is 20h, and then the furnace is cooled.
In this embodiment, mo is approximately equiaxed grains 2 FeB 2 The preparation method of the base metal ceramic is simple and the cost is lowIs low in cost. The obtained metal ceramic microstructure and mechanical properties are respectively as follows: the shape factor of the crystal grain is 0.79, the bending strength is 1681.8MPa, and the fracture toughness is 14.3MPa m 1/2 。
Example 3:
selecting Mo, feB and Fe powder with purity not lower than 99.0% to prepare powder, wherein the powder comprises the following components in percentage by weight: mo:55.0%, feB:26.0%, fe:19.0%; ball milling the mixed powder, drying and compacting the mixed powder to prepare a cylindrical (diameter 44mm, height 8-9 mm) blank; then placing the blank into a vacuum carbon tube furnace for sintering, wherein the specific technological parameters are as follows: the temperature rising rate from room temperature to sintering temperature I is 15 ℃/min, the sintering temperature I is 1150 ℃, the heat preservation time I is 60min, the temperature reducing rate from the sintering temperature I to the sintering temperature II is 15 ℃/min, the sintering temperature II is 1090 ℃, the heat preservation time II is 30h, and then the furnace is cooled.
In this embodiment, mo is approximately equiaxed grains 2 FeB 2 The preparation method of the base metal ceramic is simple and the cost is low. The obtained metal ceramic microstructure and mechanical properties are respectively as follows: the shape factor of the crystal grain is 0.72, the bending strength is 1396.8MPa, and the fracture toughness is 13.9MPa m 1/2 。
Comparative example 1:
the comparative example used the same raw material composition as in example 1, except that the sintering process parameters were 1100 ℃ for 10 hours and 10 minutes. The obtained product has bad deadly and extremely high brittleness.
Comparative example 2:
the comparative example used the same raw material composition as in example 1, except that the sintering process used the existing conventional sintering process, and the specific process parameters were: the temperature rising rate from room temperature to the highest sintering temperature is 5 ℃/min, the highest sintering temperature is 1280 ℃, the heat preservation time is 35min, and the furnace is directly cooled after heat preservation.
Mo obtained in comparative example 2 FeB 2 The metal ceramic microstructure (see figure 3) and the mechanical properties of the base metal are respectively: the shape factor of the crystal grain is 0.66, the bending strength is 1334.3MPa, and the fracture toughness is 13.5MPa m 1/2 。
Mo of the above examples and comparative examples 2 FeB 2 The test properties of the base cermets are shown in Table 1.
Table 1 Mo 2 FeB 2 Base metal ceramic microstructure and mechanical properties
| Sample of | Shape factor | Flexural Strength/MPa | Fracture toughness/MPa.m 1/2 |
| Comparative example 2 | 0.66 | 1334.3 | 13.5 |
| Example 1 | 0.83 | 1812.4 | 14.6 |
| Example 2 | 0.79 | 1681.8 | 14.3 |
| Example 3 | 0.72 | 1396.8 | 13.9 |
From FIG. 3, it can be seen that Mo has been prepared by the conventional sintering process 2 FeB 2 The grains of the base metal ceramic are long columns, and as can be seen from fig. 2, the grains of the metal ceramic prepared by the novel sintering process grow in a nearly equiaxial shape. As can be seen from the test results of Table 1, the novel sintering process can increase the form factor of the grains, indicating that Mo can be weakened 2 FeB 2 The grain directional growth degree is approximately equiaxial, the hardness and the bending strength of the metal ceramic are both increased, the bending strength is improved by about 35.8% at the highest, and the comprehensive mechanical property is greatly improved compared with that of comparative example 2.
Claims (3)
1. Nearly equiaxial grain Mo 2 FeB 2 The preparation method of the base metal ceramic is characterized by comprising the following steps: ball milling, drying and compression molding are sequentially carried out on mixed powder of Mo, feB and Fe to prepare a green body, and then sintering is carried out on the green body, wherein the sintering process comprises the following steps: the temperature rising rate from room temperature to sintering temperature I is 5-15 ℃/min, the sintering temperature I is 1100-1150 ℃, the heat preservation time I is 10-60 min, the cooling rate from the sintering temperature I to sintering temperature II is 1-15 ℃/min, the sintering temperature II is 950-1090 ℃, the heat preservation time II is 10-30 h, and then the furnace is cooled;
the weight percentages are as follows: 44.0 to 55.0 percent of Mo, 25.0 to 34.0 percent of FeB and 13.0 to 25.0 percent of Fe.
2. The near equiaxed grain Mo according to claim 1 2 FeB 2 The preparation method of the base metal ceramic is characterized in that the sintering is performed in a vacuum carbon tube furnace.
3. The near equiaxed grain Mo according to claim 2 2 FeB 2 A method for producing a base cermet, characterized in that the Mo 2 FeB 2 The shape factor of the crystal grains of the base metal ceramic is 0.72-0.83; the bending strength of the metal ceramic is 1396.8-1812.4 MPa, and the fracture toughness is 13.9-14.6MPa.m 1/2 。
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003205352A (en) * | 2002-01-08 | 2003-07-22 | Toyo Kohan Co Ltd | Member for molten metal, composed of sintered alloy having excellent corrosion resistance and wear resistance to molten metal, its producing method and machine structural member using it |
| WO2012133328A1 (en) * | 2011-03-30 | 2012-10-04 | 東洋鋼鈑株式会社 | Hard sintered alloy |
| CN104451325A (en) * | 2014-12-12 | 2015-03-25 | 西安交通大学 | Process for preparing Mo2FeB2-based metal ceramic |
| CN109825754A (en) * | 2019-02-11 | 2019-05-31 | 西安交通大学 | A kind of modified Mo2FeB2Based ceramic metal and preparation method thereof |
| CN109868382A (en) * | 2019-02-11 | 2019-06-11 | 西安交通大学 | A kind of rare-earth element modified Mo2FeB2Based ceramic metal and preparation method thereof |
| CN110218928A (en) * | 2019-06-28 | 2019-09-10 | 南京航空航天大学 | A kind of high-strength tenacity Mo2FeB2Based ceramic metal and preparation method thereof |
| CN113930760A (en) * | 2021-09-28 | 2022-01-14 | 西安迈瑞驰石油科技有限公司 | Laser cladding boride-based wear-resistant coating and preparation method and application thereof |
| CN114318038A (en) * | 2021-12-01 | 2022-04-12 | 三峡大学 | Boride modified Mo2FeB2Base cermet and method for preparing same |
-
2022
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Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003205352A (en) * | 2002-01-08 | 2003-07-22 | Toyo Kohan Co Ltd | Member for molten metal, composed of sintered alloy having excellent corrosion resistance and wear resistance to molten metal, its producing method and machine structural member using it |
| WO2012133328A1 (en) * | 2011-03-30 | 2012-10-04 | 東洋鋼鈑株式会社 | Hard sintered alloy |
| CN104451325A (en) * | 2014-12-12 | 2015-03-25 | 西安交通大学 | Process for preparing Mo2FeB2-based metal ceramic |
| CN109825754A (en) * | 2019-02-11 | 2019-05-31 | 西安交通大学 | A kind of modified Mo2FeB2Based ceramic metal and preparation method thereof |
| CN109868382A (en) * | 2019-02-11 | 2019-06-11 | 西安交通大学 | A kind of rare-earth element modified Mo2FeB2Based ceramic metal and preparation method thereof |
| CN110218928A (en) * | 2019-06-28 | 2019-09-10 | 南京航空航天大学 | A kind of high-strength tenacity Mo2FeB2Based ceramic metal and preparation method thereof |
| CN113930760A (en) * | 2021-09-28 | 2022-01-14 | 西安迈瑞驰石油科技有限公司 | Laser cladding boride-based wear-resistant coating and preparation method and application thereof |
| CN114318038A (en) * | 2021-12-01 | 2022-04-12 | 三峡大学 | Boride modified Mo2FeB2Base cermet and method for preparing same |
Non-Patent Citations (1)
| Title |
|---|
| 气压烧结工艺对Mo2FeB2基金属陶瓷组织和 性能的影响;董彪 等;《硬质合金》;第36卷(第1期);38-43 * |
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