JP2006336048A - Cemented carbide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide cemented carbide by which, even in the case that, after being joined to a base material (basis material) by welding or brazing, the resultant joined object (joined material) is subjected to holding at a high temperature, cracking and deterioration in wear resistance after the high temperature holding can be prevented. <P>SOLUTION: (1) The cemented carbide uses Co and/or Ni as a binding material, and in which WC is dispersed in the binding material, and further, the particle size of the WC is 1.5 to 4μm and the total content of the Co and/or Ni is 25 to 45 mass% and 6 to 25 mass% W is contained in the binding material. (2) The cemented carbide is produced by substituting not more than 15 vol.% of the WC with fine powder of 0.3 to 3μm particle size composed of one or more kinds among the carbides, nitrides and carbonitrides of at least one element selected from Ti, Ta, Nb, V and Cr. (3) The cemented carbide is used by being joined to the surface of the basis material of a sliding member. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to a technical field related to cemented carbide, and in particular, a technology related to cemented carbide used by being joined (welded, brazed) to the surface thereof in order to improve the wear resistance of the sliding member. Belongs to the field.

  Japanese Patent Application Laid-Open No. 7-126792 (Patent Document 1) discloses a cemented carbide in which WC is dispersed in a binder made of Co and / or Ni, and the particle size of the WC is 0.3 to 3 μm, A cemented carbide for welding is described, wherein the total content of Co and / or Ni is 25 to 45% by mass. Further, 15% by volume or less of WC in the cemented carbide is a grain composed of at least one element selected from Ti, Ta, Nb, V, and Cr, nitride, and carbon / nitride. The one substituted with fine powder having a diameter of 0.3 to 3 μm is described.

These cemented carbides do not cause defects such as cracks in the welded part and the weld heat-affected zone, have excellent weldability and good wear resistance. Therefore, these cemented carbides can be widely used for welding forming and repairing various wear parts, such as cutting tips, drawing dies, wear parts of civil engineering construction machines (well drilling bit rock drills, etc.) and mechanical seals. It can be widely used for welding and repairing wear parts such as sliding wear parts and dies.
Japanese Patent Application Laid-Open No.7-126792

  The cemented carbide described in Japanese Patent Application Laid-Open No. 7-126792 has excellent weldability and good wear resistance as described above. However, when it is held at a high temperature after being joined by welding or brazing, cracks may occur in the joint interface or cemented carbide of the joint after this high temperature holding, or the wear resistance may deteriorate. That is, in the utilization place as exemplified above, the cemented carbide is joined to the base material (base material) by welding or brazing and then joined (hereinafter also referred to as a joining material). Is sometimes used in a high temperature environment and kept at a high temperature. Thus, when the bonding material is held at a high temperature, even if the cemented carbide of the bonding material is the cemented carbide described in the above publication, Cracks may occur at the cemented carbide or joint (welding, brazing) joint interface, and wear resistance may deteriorate.

  The present invention has been made paying attention to such circumstances, and its purpose is to join the base material (base material) by welding or brazing and then join the base material (joining material). Therefore, the present invention intends to provide a cemented carbide capable of suppressing the generation of cracks and the deterioration of wear resistance after maintaining at a high temperature.

  In order to achieve the above object, the present inventors have intensively studied, and as a result, completed the present invention. According to the present invention, the above object can be achieved.

  The present invention, which has been completed in this way and has achieved the above object, relates to a cemented carbide, and the cemented carbide according to claims 1 to 3 of the claims (superstructures according to the first to third inventions). Hard alloy), which has the following configuration.

  That is, the cemented carbide according to claim 1 is a cemented carbide in which Co and / or Ni is used as a binder and WC is dispersed in the binder, and the grain size of the WC is 1.5 to 4 μm. The cemented carbide is characterized in that the total content of Co and / or Ni is 25 to 45% by mass, and W is contained in the binder by 6 to 25% by mass [first invention]. .

  The cemented carbide according to claim 2, wherein at least 15% by volume of the WC is one of carbide, nitride, and carbon / nitride of at least one element selected from Ti, Ta, Nb, V, and Cr. The cemented carbide according to claim 1, wherein the cemented carbide is replaced with a fine powder having a particle size of 0.3 to 3 µm [second invention].

  The cemented carbide according to claim 3 is the cemented carbide according to claim 1 or 2 used by being bonded to the surface of the base material of the sliding member [third invention].

  According to the cemented carbide according to the present invention, after this is joined to the base material (base material) by welding or brazing, even if this joined material (joining material) is kept at a high temperature, Generation of cracks after holding at high temperature and deterioration of wear resistance can be suppressed. That is, even after such high temperature holding, cracks are hardly generated and wear resistance is not easily deteriorated.

  As described above, the cemented carbide according to the present invention is a cemented carbide in which Co and / or Ni is used as a binder and WC is dispersed in the binder, and the grain size of the WC is 1.5. The cemented carbide is characterized in that the total content of Co and / or Ni is 25 to 45% by mass and W is contained in the binder by 6 to 25% by mass. .

  In the cemented carbide according to the present invention, the total content of Co and / or Ni contained as a binder as described above is specified as 25 to 45 mass%, and the particle size of WC dispersed in the binder is determined. In addition to being specified as 1.5 to 4 μm, W is included in the binder, and the content of W is specified as 6 to 25% by mass. Hereinafter, the specific reason will be described.

  Co and Ni in the cemented carbide are binders, and support and fix the WC fine powder as a matrix component of the cemented carbide and exhibit an effect of reducing the cracking sensitivity. Co and / or Ni If the total content of is less than 25% by mass (% by weight), the cracking sensitivity becomes sensitive, and cracking is likely to occur in the bonded portion of the bonding material or the cemented carbide. However, if the total content of Co and / or Ni exceeds 45% by mass, deformation is likely to occur in the sintering process when a cemented carbide alloy body is produced by powder metallurgy, and a molded body having a predetermined shape and size. Not only becomes difficult to obtain, but also the wear resistance tends to be insufficient due to the relatively low content of WC. Accordingly, the total content of Co and / or Ni is specified as 25 to 45% by mass.

  The particle size of WC dispersed in the binder is closely related to the wear resistance of the cemented carbide. If the WC particle size is a coarse particle having a particle size of more than 4 μm, the WC particles may fall off during use. Since it tends to occur, sufficient wear resistance cannot be obtained. On the other hand, if the WC particle size is less than 1.5 μm, the hardness is increased and the sensitivity to cracking becomes sensitive, and cracking is likely to occur in the joint or cemented carbide. Therefore, the particle size of WC is specified as 1.5 to 4 μm.

  W contained in the binder affects recrystallization during holding at a high temperature such as aging after bonding, and when W is not contained in the binder, or even if W is contained, the W content When the amount is less than 6% by mass, the binder recrystallizes during the high temperature holding such as aging treatment after the joining, and pores accumulate, resulting in deterioration of wear resistance. In order to prevent deterioration of wear resistance due to pore accumulation due to such recrystallization, the W content needs to be 6% by mass or more. In order to prevent deterioration of the wear resistance at a higher level, it is desirable that the content be 10% by mass or more.

When the added amount of W exceeds 25% by mass, the η phase [: eta phase (Co ₃ W ₃ C)] is likely to be generated, and the mechanical properties are deteriorated.

  Accordingly, W is contained in the binder, and the content of W is specified to be 6 to 25% by mass.

  For the reasons described above, the cemented carbide according to the present invention includes the total content of Co and / or Ni contained as a binder as described above, the particle size of WC dispersed in this binder, and this bond. The content of W in the material is specified. Therefore, even when the bonding material is held at a high temperature after being joined to the base material (base material) by welding or brazing, generation of cracks and deterioration of wear resistance after the high temperature holding can be suppressed. . That is, even after such high temperature holding, cracks are hardly generated and wear resistance is not easily deteriorated.

  In addition, after joining, when a joining material is hold | maintained at high temperature, the case where a joining material receives an aging treatment other than the case where a joining material is used in a high temperature environment and kept at high temperature is included. This aging treatment is performed when the base material (base material) is a precipitation hardening (type) metal such as SUS630. Even when the cemented carbide joining material according to the present invention is subjected to such an aging treatment, the occurrence of cracks and the deterioration of the wear resistance after the aging treatment hardly occur.

  15% by volume or less of the WC has a particle size of 0.3 to 3 μm composed of at least one of carbide, nitride, and carbon / nitride of at least one element selected from Ti, Ta, Nb, V, and Cr. By substituting with the fine powder, it is possible to improve wear resistance, high temperature strength, toughness, oxidation resistance, corrosion resistance, etc. [second invention]. In addition, when it exceeds 15 volume% of WC and it substitutes with these fine powders, it will become easy to produce a crack in the junction part of a joining material.

  The cemented carbide according to the present invention can be used by being joined to the surface of the base material of the sliding member [third invention]. In this case, even when the sliding member is held at a high temperature, the generation of cracks and the deterioration of wear resistance after the high temperature holding are unlikely to occur.

  The type of the substrate to which the cemented carbide according to the present invention is joined is not particularly limited, but steel is usually used.

  Examples of the present invention and comparative examples will be described below. The present invention is not limited to this embodiment, and can be implemented with appropriate modifications within a range that can be adapted to the gist of the present invention, all of which are within the technical scope of the present invention. include.

Co powder, Ni powder, Cr ₃ C ₂ powder, WC powder and W powder are mixed so that the total weight is 1 kg, and 5 kg of carbide balls and 700 CC of hexane are added to it and mixed in an attritor for 4 hours. did. After removing the cemented carbide balls from the mixture and drying the mixture, the mixture was formed into a green compact of 75 × 75 × 8 mm at a pressure of 1 ton / cm ^2. Sintered for a time to obtain a sintered body (super hard alloy).

  The sintered body (superhard alloy) thus obtained was subjected to heat treatment simulating the thermal history during joining by brazing. In addition, after this heat treatment, high temperature holding was performed assuming use in a high temperature environment. At this time, the heat treatment simulating the thermal history at the time of joining was held at 760 ° C. for 30 minutes, then held at 850 ° C. for 10 minutes, and then furnace-cooled. The high temperature was held at 300 ° C. for 5 hours. The furnace was cooled after maintaining the high temperature.

  About these materials (super hard alloy), the composition analysis by SEM (scanning electron microscope), structure | tissue observation (WC particle size measurement), and the sliding test were done. The composition analysis was performed using the cemented carbide after the heat treatment. The structure observation was performed on the sintered body (after sintering). The sliding test was performed for each of the cemented carbide after the heat treatment and the cemented carbide after the high temperature holding.

  At this time, composition analysis and WC particle size measurement were performed as follows. A specimen was cut out from the cemented carbide after the heat treatment, the cut surface of the specimen was mirror-polished, and then observed with an SEM (Hitachi S-4500) at an acceleration voltage of 20 kV. At this time, a beam was applied to the binder, and quantitative analysis of W, C, Ni, and Co was performed by EDX. For WC particle size measurement, photographs taken at a magnification of 2000 by SEM are analyzed by image analysis (NanoSystem Co., Ltd. NanoHunter NS2K-Lt; Kobelco Research Institute specification) and WC grain (observed white) and binder (observed black) ) And binarized, and the average particle size was calculated.

  The sliding test was performed by a vane on disk test. Details of this test will be described below. The test piece vane had a total length of 20 mm, a thickness of 3.5 mm, and a width of 5 mm, and a test piece having one end at R4 (0.8S finish) was prepared. The disc was made of cermet and had a diameter of 50 mm x thickness of 6.5 mm. The disc friction surface was mirror-polished to Ra0.01 µm. The sliding tester is FPD-100BD-J manufactured by Tokyo Test Machine Co., Ltd., and two vanes (test pieces) are mounted on the upper anvil symmetrically around the circumference of the diameter of 30mm, and the bottom of the container The anvil was rotated at 1 m / sec by contacting with a 300 N load to a disk mounted to be fixed to the disk. The sliding distance is 500m. The change in the weight of the vane before and after the sliding test was measured, and the average of the two was taken as the amount of wear.

  On the other hand, the cemented carbide after the heat treatment was joined to the base material SUS410 by brazing, and a crack test was performed to check the occurrence of cracks. At this time, with regard to brazing, the insert material (silver brazing containing Ti), the stress relaxation material (oxygen-free copper), and the insert material are sandwiched between the cemented carbide and the base material (SUS 410) and laminated. This was performed by holding at 760 ° C. for 30 minutes in a vacuum and then holding at 850 ° C. for 10 minutes. With respect to the bonding material thus obtained, SEM observation samples were collected, and the occurrence of cracks in the cemented carbide and the bonding interface between the bonded portion and the substrate were examined by SEM observation.

  Further, the bonding material obtained by brazing was held at a high temperature assuming that it was used in a high temperature environment. At this time, the high temperature was held at 300 ° C. for 5 hours. In addition, it cooled naturally after holding high temperature. Thereafter, an SEM observation sample was taken from this bonding material, and the occurrence of cracks at the cemented carbide and the bonded interface between the bonded portion and the substrate was examined by SEM observation.

  Table 1 shows the results of the above tests (composition analysis, structure observation, sliding test, and investigation test of crack occurrence by brazing).

In Table 1, the Co amount (wt%) and Ni amount (wt%) in the column of binder amount are both wt% (wt%) in the cemented carbide, and the total amount (wt%) is The total amount (wt%) of the Co amount (wt%) and the Ni amount (wt%), that is, the total content (wt%) of the binder. Cr ₃ C ₂ content (vol%) is the percentage of WC amount (vol) and the Cr ₃ C ₂ weight relative to the total amount (vol) of Cr ₃ C ₂ content (vol) (vol) (% by volume). The amount of W (wt%) is weight% (wt%) in the binder (Co and Ni).

  The wear resistance is indicated by the amount of wear (mg) by the sliding test described above. The smaller the wear amount (mg), the better the wear resistance. Abrasion resistance after joining is a result of a sliding test on the cemented carbide after the heat treatment (a cemented carbide subjected to a heat treatment simulating a heat history during joining by brazing), that is, wear resistance. The wear resistance after holding at a high temperature is the result of a sliding test on the cemented carbide after holding the high temperature (the cemented carbide that has been held at a high temperature after the heat treatment), that is, the wear resistance.

  The thing after joining in the column of a crack is the SEM observation result about the thing after joining by the above-mentioned brazing, ie, the generation | occurrence | production condition of a crack (crack). The one after holding at high temperature is the result of SEM observation of the one after holding the bonding material obtained by brazing described above at high temperature, that is, the occurrence of cracks. ○ indicates that there is no crack, △ indicates that a small crack with a level that does not cause a problem as a member is observed (although cracks are observed, but the degree is minor and has no problem), × indicates that a crack has been confirmed as a member It indicates what is unusable.

  As can be seen from Table 1, when the particle size of WC is small and does not satisfy 1.5 to 4 μm, the crack occurrence state is Δ after joining by brazing, but the crack occurrence state is × after holding at high temperature. Yes, x level cracks were observed (No.1: comparative example). In addition, this crack was recognized by the cemented carbide alloy and the joining interface.

  When the particle size of WC is large and does not satisfy 1.5 to 4 μm, both after bonding and after holding at high temperature have a large amount of wear, and wear resistance is low and insufficient (No. 5: comparison) Example).

  On the other hand, when the particle size of WC satisfies 1.5 to 4 μm, the crack occurrence state is ◯ in both the bonded state and the one after holding at high temperature, no cracks are observed, and the wear resistance is improved. Excellent (No. 2 to 4: Example of the present invention).

  When the content (solid solution amount) of W in the binder is small and does not satisfy 6 to 25% by mass, the crack occurrence is ○ after bonding and after holding at high temperature. As for the wear resistance, the one after bonding is good, but the one after holding at a high temperature has a very large amount of wear and the wear resistance is remarkably low (No. 6: comparative example). This remarkable decrease in wear resistance after holding at high temperature is due to the fact that the binder recrystallizes due to holding at high temperature, pores accumulate, and voids are generated.

  On the other hand, when the W content (solid solution amount) in the binder satisfies 6 to 25% by mass, the one after holding at high temperature is also excellent in wear resistance (No. 7 to 10: Example of the present invention). ). That is, both the bonded state and the high-temperature held state are ◯ for crack occurrence, no cracks are observed, good wear resistance, and excellent wear resistance.

  When the total content (total amount) of the binder (Co and Ni) does not satisfy 25 to 45% by mass, the crack generation state is x after bonding and after holding at high temperature, and x level cracks were observed. (No. 11: comparative example). In addition, this crack was recognized by the cemented carbide alloy and the joining interface.

  On the other hand, when the total content of the binder (Co and Ni) satisfies 25 to 45% by mass, the crack generation state is ◯ after bonding and after holding at high temperature, and no crack is observed (No. 12 to 15: Example of the present invention).

Nos. 16 to 18 are test results when the ratio of Co amount / Ni amount is changed (example of the present invention). No.19 is to 22 ones, a test result in the case of changing Cr ₃ C ₂ amount (vol%) (present invention examples). If the amount of Cr ₃ C ₂ exceeds 15 vol%, cracks may easily occur at the joint of the joining material after joining and after holding at high temperature, but all of No. 19 to 22 have Cr ₃ C ₂ content. It is 15 vol% or less, and the crack occurrence is good after joining and holding at high temperature, and no crack is observed.

  In addition, when forming the above-mentioned mixture into a green compact, if HIP (hot isostatic pressing) is performed, the density of the sintered body is improved and the wear resistance is improved.

The cemented carbide according to the present invention is bonded to a base material (base material) by welding or brazing, and even when this joining material is kept at a high temperature, generation of cracks and resistance to the high temperature are maintained. Since the wear resistance hardly occurs, it can be suitably used when the bonding material is held at a high temperature such as when used in a high temperature environment or when an aging treatment is performed.

Claims (3)

  A cemented carbide in which Co and / or Ni is used as a binder, and WC is dispersed in the binder, and the particle size of the WC is 1.5 to 4 μm, and the total content of Co and / or Ni is A cemented carbide characterized by being 25 to 45 mass% and containing 6 to 25 mass% of W in the binder.   15% by volume or less of the WC has a particle size of 0.3 to 3 μm composed of at least one of carbide, nitride, and carbon / nitride of at least one element selected from Ti, Ta, Nb, V, and Cr. The cemented carbide according to claim 1, wherein the cemented carbide is replaced with a fine powder. The cemented carbide according to claim 1 or 2, wherein the cemented carbide is used by being bonded to the surface of the base material of the sliding member.