Method for adjusting pore size of porous metal material and pore structure of porous metal material

Abstract

Disclosed are a method for adjusting the pore size of a porous metal material and the pore structure of a porous metal material. The method comprises: permeating at least one element into the surface of the pores of the material to generate a permeated layer on the surface of the pores, so that the average pore size of the porous material is reduced to within a certain range, thus obtaining a pore structure of the porous metal material having the pores distributed on the surface of the material and the permeated layer provided on the surface of the pores.

Claims

1. A method for treating a surface of a TiAl intermetallic compound porous material to decrease its pore diameters, which comprises: exposing the TiAI intermetallic compound porous material in an active carburizing atmosphere at a temperature of 8001200 C. for 112 hours while maintaining carbon potential at 0.81.0%.

2. A method for treating a surface of NiAl intermetallic compound porous material to decrease its pore diameters, which comprises: exposing the NiAl intermetallic compound porous material in an active carburizing atmosphere at a temperature of 8001200 C. for 210 hours while maintaining carbon potential at 1.01.2%.

3. A method for treating a surface of FeAl intermetallic compound porous material to decrease its pore diameters, which comprises: exposing the FeAl intermetallic compound porous material in an active carburizing atmosphere at a temperature of 8001200C. for 19 hours while maintaining carbon potential at 0.81.2%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic plan view of the pore structure of the porous metal materials of the invention.

(2) FIG. 2 is a sectional view along A-A in FIG. 1.

(3) FIG. 3 are the curves of average pore diameter changes for TiAl and NiAl materials carburized separately at different temperatures for 6 hours.

(4) FIG. 4 is the average pore diameter plotted as a function of carburization time at 900 C. for TiAl material

(5) FIG. 5 is the average pore diameter plotted as a function of carburization time at 940 C. for NiAl material

(6) FIG. 6 are the corrosion resistance kinetics curves of TiAl material before and after nitriding.

(7) In the FIGS., 1 is the pore, and 2 is the permeated layer.

EMBODIMENTS

(8) Below, the methods of the current invention for adjusting pore diameters are explained further through the multiple groups of embodiments.

(9) Embodiment 1

(10) The first group of embodiments treated titanium porous materials with carburizing, nitriding and carbonitriding processes separately. Before the carburizing, nitriding and carbonitriding porcesses, the initial average pore diameter of the materials was 20 m, and the initial porosity of the materials was 30%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 1.

(11) TABLE-US-00001 TABLE 1 Pore structure of the material after the Carbon chemical- potential thermal treatment Chemical- and/or Average thermal Temperature Time nitrogen pore Porosity treatment ( C.) (h) potential (%) diameter (%) Carburization 850 1 1.0 19.2 27.6 3 18.9 26.8 5 18.4 25.4 7 17.8 23.8 950 1 1.0 16.4 20.1 3 14.0 14.7 5 13.2 13.1 7 11.0 9.0 Nitridation 850 4 1.0 19.3 27.9 8 18.7 27.6 12 18.0 24.3 16 17.5 22.9 950 4 1.0 16.0 19.2 8 13.6 13.9 12 12.6 11.9 16 10.6 8.4 carbonitriding 850 2 1.0 19.6 28.8 4 19.0 26.9 6 18.3 25.1 8 18.0 24.3 950 2 1.0 17.1 22.2 4 16.2 19.7 6 15.4 17.8 8 13.8 13.9

(12) Embodiment 2

(13) The second group of embodiments treated TiAl intermetallic compound porous materials with carburizing processes. Before the carburizing processes, the initial average pore diameter of the materials was 15 m, and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatment and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 2.

(14) TABLE-US-00002 TABLE 2 Pore structure of the material after chemical-thermal treatment Carbon Average pore Permeated layer Chemical-thermal Temperature Time potential diameter Porosity thickness treatment ( C.) (h) (%) (m) (%) (m) Carburization 800 1 1.0 14.6 42.6 1 3 13.7 37.5 6 13.2 34.8 9 12.8 32.8 12 12.3 30.2 900 1 1.0 14.5 42.0 3 13.4 35.9 6 12.9 33.3 9 12.3 30.3 12 11.6 26.9 1000 1 1.0 14.2 40.3 3 13.1 34.4 6 12.7 32.2 9 11.6 26.9 12 11.1 24.6 1100 1 1.0 13.5 36.4 3 12.7 32.2 6 12.0 28.8 9 11.1 24.6 12 10.2 20.8 1200 1 1.0 12.8 32.8 3 12.1 29.3 6 11.2 25.1 9 10.2 20.8 12 9.3 17.3 30

(15) Embodiment 3

(16) The third group of embodiments treated TiAl intermetallic compound porous materials with nitriding processes. Before the nitriding processes, the initial average pore diameter of the materials was 15 m, and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 3.

(17) TABLE-US-00003 TABLE 3 Pore structure of the material after chemical-thermal treatment Nitrogen Average pore Permeated layer Chemical-thermal Temperature Time Potential diameter Porosity thickness treatment ( C.) (h) (%) (m) (%) (m) Nitridation 800 4 1.0 14.5 42.0 0.5 8 13.8 38.0 12 13.0 33.8 16 12.7 32.3 20 12.2 29.8 850 4 1.0 14.3 40.9 8 13.5 36.4 12 12.7 32.2 16 12.2 29.8 20 11.8 27.8 900 4 1.0 14.0 39.2 8 13.1 34.3 12 12.3 30.2 16 11.4 26.0 20 11.2 25.1 950 4 1.0 13.4 35.9 8 12.6 31.7 12 11.6 26.9 16 10.4 21.6 20 10.3 21.2 1000 4 1.0 12.9 33.0 8 12.2 29.8 12 11.1 24.6 16 9.9 19.6 20 9.0 16.2 20

(18) Embodiment 4

(19) The fourth group of embodiments treated TiAl intermetallic compound porous materials with carbonitriding processes. Before the carbonitriding processes, the initial average pore diameter of the materials was 15 m and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 4.

(20) TABLE-US-00004 TABLE 4 Carbon potential Pore structure of the material after the chemical-thermal and nitrogen Average pore Permeated layer Chemical-thermal Temperature Time potential diameter Porosity thickness treatment ( C.) (h) (%) (m) (%) (m) Carbonitriding 800 1 1.0 14.8 43.8 0.5 4 14.1 39.8 8 13.1 34.3 12 12.6 31.8 16 12.0 28.8 850 1 1.0 14.7 43.2 4 13.6 36.9 8 12.8 32.7 12 12.1 29.3 16 11.5 26.4 900 1 1.0 14.3 40.9 4 13.2 34.8 8 12.2 29.8 12 11.3 25.5 16 11.0 24.2 950 1 1.0 13.6 36.9 4 12.5 31.2 8 11.4 26.0 12 10.5 22.0 16 10.0 20.0 1000 1 1.0 13.1 34.3 4 12.0 28.8 8 10.4 21.6 12 9.7 18.8 16 9.0 16.2 25

(21) Embodiment 5

(22) The fifth group of embodiments treated porous TiAl materials with boronization processes. Before the boronization processes, the initial average pore diameter of the materials was 15 m and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 5.

(23) TABLE-US-00005 TABLE 5 Pore structure of the material after the chemical- thermal treatment Average Chemical- Boron pore thermal Temperature Time potential diameter treatment ( C.) (h) (%) (m) Porosity (%) Boronization 800 5 1.0 14.4 41.5 10 13.6 36.9 15 12.9 33.3 20 12.4 30.7 25 11.8 27.8 850 5 1.0 14.2 40.3 10 13.3 35.4 15 12.6 31.7 20 11.9 28.3 25 11.4 25.9 900 5 1.0 13.9 38.6 10 12.9 33.3 15 12.1 29.3 20 11.2 25.1 25 10.7 22.9 950 5 1.0 13.2 34.8 10 12.4 30.7 15 11.3 25.5 20 10.3 21.2 25 9.8 19.2 1000 5 1.0 12.7 32.3 10 12.0 28.8 15 10.5 22.0 20 9.4 17.6 25 8.8 15.5

(24) Embodiment 6

(25) The sixth group of embodiments treated NiAl intermetallic compound porous materials with carburizing processes. Before the carburizing processes, the average pore diameter of the materials was 15 m and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 6.

(26) TABLE-US-00006 TABLE 6 Pore structure of the materials after chemical-thermal treatment Carbon Average pore Permeated layer Chemical-thermal Temperature Time potential diameter Porosity thickness treatment ( C.) (h) (%) (m) (%) (m) Carburization 800 2 1.0 14.2 40.3 0.5 4 13.6 36.9 6 13.3 35.4 8 13.1 34.3 10 12.9 33.3 900 2 1.0 14.0 39.2 4 13.2 34.8 6 12.8 32.8 8 12.6 31.8 10 12.5 31.3 1000 2 1.0 13.8 38.1 4 13.0 33. 6 12.3 30.3 8 11.8 27.8 10 11.5 28.3 1100 2 1.0 13.4 35.9 4 12.5 31.2 6 11.8 27.8 8 11.5 26.4 10 10.9 23.8 1200 2 1.0 13.0 33.8 4 12.2 29.8 6 11.3 25.5 8 10.5 22.1 10 10.1 20.4 25

(27) Embodiment 7

(28) The seventh group of embodiments treated NiAl intermetallic compound porous materials with nitriding processes. Before the nitriding processes, the average pore diameter of the materials was 15 m and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 7.

(29) TABLE-US-00007 TABLE 7 Pore structure of the material after chemical-thermal treatment Nitrogen Average pore Permeated layer Chemical-thermal Temperature Time potential diameter Porosity thickness treatment ( C.) (h) (%) (m) (%) (m) Nitridation 700 2 1.0 14.8 43.8 0.5 8 14.7 43.2 14 14.7 43.2 20 14.6 42.6 26 14.5 42.0 750 2 1.0 14.6 42.6 8 14.3 40.9 14 14.0 39.2 20 13.8 38.1 26 13.7 37.5 800 2 1.0 14.2 40.3 8 13.4 35.9 14 12.6 31.7 20 12.1 29.3 26 11.6 26.9 850 2 1.0 13.7 37.5 8 12.7 32.3 14 12.0 28.8 20 11.6 26.9 26 11.1 24.6 900 2 1.0 13.2 34.8 8 12.4 30.3 14 11.5 26.4 20 10.6 22.5 26 10.3 21.2 15

(30) Embodiment 8

(31) The eighth group of embodiments treated porous NiAl intermetallic compound porous materials with carbonitriding processes. Before the carbonitriding processes, the average pore size of the materials was 15 m and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 8.

(32) TABLE-US-00008 TABLE 8 Pore structure of the materials after chemical-thermal treatment Carbon potential Average pore Permeated layer Chemical-thermal Temperature Time and nitrogen diameter Porosity thickness treatment ( C.) (h) potential (%) (m) (%) (m) Carbonitriding 750 2 1.0 14.6 42.6 0.5 6 14.3 40.9 10 14.1 39.8 14 14.0 39.2 18 13.9 38.6 800 2 1.0 14.3 40.9 6 13.9 38.6 10 13.5 36.4 14 13.2 34.8 18 13.0 33.8 850 2 1.0 14.0 39.2 6 13.3 35.4 10 12.4 30.7 14 11.9 28.3 18 11.4 25.9 900 2 1.0 13.6 36.9 6 12.6 31.7 10 11.7 27.4 14 11.4 25.9 18 10.9 23.8 950 2 1.0 13.1 34.3 6 12.1 29.3 10 11.2 25.1 14 10.4 21.6 18 10.2 20.8 20

(33) Embodiment 9

(34) The ninth group of embodiments treated porous NiAl intermetallic compound porous materials with boronization processes. Before the boronization processes, the initial average pore diameter of the materials was 15 m and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 9.

(35) TABLE-US-00009 TABLE 9 Pore structure of the material after the chemical-thermal treatments Average Chemical- pore thermal Temperature Time Boron size treatment ( C.) (h) potential (%) (m) Porosity (%) Boronization 650 2 1.0 14.9 44.4 6 14.8 43.8 10 14.7 43.2 14 14.6 42.6 18 14.5 42.0 750 2 1.0 14.6 42.6 6 14.3 40.9 10 13.9 38.6 14 13.7 37.5 18 13.6 37.0 850 2 1.0 14.1 39.8 6 13.5 36.4 10 12.7 32.3 14 12.3 30.3 18 11.8 27.8 950 2 1.0 13.7 37.5 6 12.6 31.7 10 12.1 29.3 14 11.8 27.8 18 11.2 25.1 1050 2 1.0 13.3 35.4 6 12.3 30.3 10 11.4 25.9 14 10.8 23.3 18 10.4 21.6

(36) Embodiment 10

(37) The tenth group of embodiments treated FeAl intermetallic compound porous materials with carburizing processes. Before the carburizing processes, the average pore diameter of the materials was 15 m and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 10.

(38) TABLE-US-00010 TABLE 10 Pore structure of the materials after the chemical-thermal treatment Carbon Average pore Permeated layer Chemical-thermal Temperature Time potential diameter Porosity thickness treatment ( C.) (h) (%) (m) (%) (m) Carburization 800 1 1.0 14.6 42.6 1 3 14.3 40.9 5 14.1 39.8 7 13.9 38.6 9 13.8 38.1 900 1 1.0 13.2 34.8 3 12.4 30.7 5 11.7 27.4 7 10.9 23.8 9 9.9 19.6 1000 1 1.0 12.6 31.7 3 11.8 27.8 5 11.1 24.6 7 10.3 21.2 9 9.5 18.1 1100 1 1.0 12.0 28.8 3 10.3 21.2 5 9.10 16.6 7 10.3 21.2 9 9.5 18.1 1200 1 1.0 10.6 22.5 3 8.3 13.8 5 7.1 10.1 7 5.9 6.90 9 5.0 5.00 50

(39) Embodiment 11

(40) The seventh group of embodiments treated FeAl intermetallic compound porous materials with nitriding processes. Before the nitriding processes, the average pore size of the materials was 15 m, and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 11.

(41) TABLE-US-00011 TABLE 11 Pore structure of the material after the chemical-thermal Nitrogen Average pore Permeated layer Chemical-thermal Temperature Time potential diameter Porosity thickness treatment ( C.) (h) (%) (m) (%) (m) Nitridation 550 2 1.0 14.7 43.2 1 6 14.3 40.9 10 14.0 39.2 14 13.8 38.1 18 13.7 37.5 600 2 1.0 14.1 39.8 6 13.5 36.5 10 12.8 32.8 14 11.9 28.3 18 11.0 24.2 650 2 1.0 13.7 37.5 6 12.9 33.3 10 12.2 29.8 14 11.4 25.9 18 10.7 22.9 700 2 1.0 13.1 34.3 6 11.2 25.1 10 10.0 20.0 14 11.4 25.9 18 10.7 22.9 750 2 1.0 11.9 28.3 6 9.20 16.9 10 7.60 11.6 14 6.40 8.20 18 5.60 6.30 25

(42) Embodiment 12

(43) The twelfth group of embodiments treated FeAl intermetallic compound porous materials with carbonitriding processes. Before the carbonitriding processes, the average pore diameter of the materials was 15 m and the initial porosity of the materials was 45%. The specific processing parameters, the average pore diameters after the chemical-thermal treatments and the porosities after the chemical-thermal treatments of this group of embodiments are shown in Table 12.

(44) TABLE-US-00012 TABLE 12 Pore structure of the material after the chemical-thermal treatment Carbon potential Average pore Permeated layer Chemical-thermal Temperature Time and nitrogen diameter Porosity thickness treatment ( C.) (h) potential (%) (m) (%) (m) Carbonitriding 700 2 1.0 14.6 43.2 1 4 14.2 40.3 6 14.0 39.2 8 13.8 38.1 10 13.6 36.9 750 2 1.0 13.6 36.9 4 12.9 33.3 6 12.0 28.8 8 11.2 25.1 10 10.6 22.5 800 2 1.0 13.1 34.3 4 12.3 33.3 6 11.3 25.5 8 10.8 23.3 10 10.3 21.2 850 2 1.0 12.4 30.8 4 10.5 22.1 6 9.40 17.7 8 10.8 23.3 10 10.3 21.2 900 2 10.9 23.8 4 1.0 8.50 14.5 6 7.40 10.9 8 6.10 7.40 10 5.10 5.20 35

(45) FIGS. 3, 4 and 5 are drawn using some of the data shown in the above 12 examples, to present the effects of temperatures and durations of time of the chemical-thermal treatments on the pore diameters. FIG. 3 shows the average pore diameter changes of TiAl and NiAl materials, respectively, after carburizing for 6 hours at different temperatures. FIG. 4 shows the average pore diameter changes with the carburizing time for TiAl material kept at 900 C. FIG. 5 is the average pore diameter change of FeAl materials kept at 940 C. for different carburizing time. It can be seen from FIGS. 3-5 that the higher the temperatures of the chemical-thermal treatments, the larger the amounts of reductions of the average pore diameters; the longer the durations of the chemical-thermal treatments, the larger the amount of reductions of the average pore diameters. Moreover, the amounts of reductions of average pore diameters of the materials obviously relate with the thickness of the permeated layers, so the thickness of the permeated layers are measured only for the first and the last experiments in each example. From the changes of the thickness of the permeated layers in the first and last experiments of each example, it can be shown that the larger the thickness of the permeated layers, the larger the amounts of reductions of the average pore diameters of the materials.

(46) Then the pore structures of the porous metal materials obtained through the methods described above will be explained in detail combined with FIG. 1 and FIG. 2.

(47) As shown in FIG. 1, the pore structures of the porous metal materials include pores 1 distributed on the surfaces of the materials, and permeated layers 2 covered on the surfaces of said pores 1. In FIG. 1 and FIG. 2, the dotted lines represents the pores before chemical-thermal treatments; the solid lines indicate the pores after chemical-thermal treatments; the region between the solid lines and dotted lines indicate the permeated layers 2. Therefore, it can be seen from FIG. 1 and FIG. 2 that the permeated layers 2 covered on the surfaces of the pores 1. During the formations of the permeated layers 2, the original pores of the porous metal materials shrinked due to the lattices distortion and inflation, thus the purpose of adjusting pore diameters is achieved. Therein, the average pore diameter of the pores 1 is best to be 0.05100 m. In addition, the porous metal materials are Al-based intermetallic compound porous materials, such as TiAl intermetallic compound porous materials, FeAl intermetallic compound porous materials or NiAl intermetallic compound porous materials. Moreover, the permeated layers 2 can be one kind of carburized layers, nitrided layers, boride layers, sulfide layers, siliconized layers, aluminized layers or chromized layers or co-permeated layers of least two of the elements described above, for instance, carbonitriding layer. On the basis of adjusting the pore diameters, the surface properties of the porous metal materials can be improved as well, such as high temperature oxidation resistance, corrosion resistance and so on.

(48) This invention can apply localized anti-permeation treatments to the porous metal materials during chemical-thermal treatments of the porous metal materials. For example, as shown in FIG. 2, sides a, b and c of the materials can be coated with anti-permeating agents, respectively, so that elements can only enter from the front of pores 1 during chemical-thermal treatments. Thus, the thickness of the permeated layers 2 on the pores 1 exhibit asymmetry from front to back, i.e., the thickness of the permeated layers 2 gradually decrease from front to back along the directions of the pores 1. Thus, the morphology of the porous metal materials is formed similarly to that of an asymmetric membrane, the pore diameters of pores 1 on one side of the surface of the porous materials are relatively smaller due to the larger thickness of the permeated layers 2, whereas the pore diameters of the pores on the other side of the surface are relatively larger due to the smaller thickness of the permeated layers (or the lack of permeated layers). When the porous materials are used for filtration, the side with relatively smaller pore diameters can be used to realize the separation of the medium to be filtered, so that the permeability of the porous metal materials and the backwash effect can be improved.

(49) The changes of the surface properties of the materials after chemical-thermal treatments are proven below through experiments. 1 The porous TiAl intermetallic compound materials carburized at 900 C. for 6 h were oxidized at 900 C. for 48 h, and then the samples were analyzed by backscattered electron (BSE) photos and spectroscopic analysis. The results show that the surfaces of the pores of the materials before and after the oxidation experiments have similar structures, indicating that the carburized layers still exhibit good thermal stability and oxidation resistance even exposed in high temperature atmosphere. 2 Corrosion experiments of TiAl intermetallic compound porous material before and after treated with nitriding at 900 C. for 12 h were conducted separately in pH=3 hydrochloric acid solutions. The results shown in FIG. 6 present the mass losses of the TiAl materials treated with nitriding are clearly lower than the TiAl materials that were not treated with nitriding as the corrosion time.