JPS63213670A - Production of wear resistant article having tungsten carbide layer - Google Patents

Abstract

PURPOSE:To prevent the peeling of a WC layer formed on each of metal parts, by mechanically polishing the surfaces of the metal parts, electropolishing them and depositing WC by chemical vapor deposition when wear resistant metal parts each having a WC layer are produced. CONSTITUTION:When a very hard WC layer having superior wear resistance is formed on the surface of each of machine parts made of a metal by chemical vapor deposition, the surfaces of the parts are made as smooth as possible by mechanical polishing such as buffing. The surfaces are then cleaned, degreased with an alkali soln. or the like and electropolished. By this electropolishing, small acute edges remaining after the mechanical polishing are removed and entirely very smooth surfaces are formed. The resulting surfaces of the metal parts 31 are chemically plated with Ni 32 and a WC layer 34 is formed on each of the plated surfaces by chemical vapor deposition after a W layer 33 is formed as required. The hard WC layer 34 having superior adhesion to each of the metal parts 31 can be stably formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a wear-resistant article having a tungsten carbide layer, and particularly a manufacturing method for forming a tungsten carbide layer with excellent durability. It is related to.

[Prior art]

Conventionally, various mechanical parts (gauges, bearings, etc.), synthetic resin molded machine parts (screws, cylinders, plungers, etc.), ceramic molding tools (screws, cylinders, molds, etc.), AI extrusion tools (various dies), and Metal mechanical parts such as hot forming tools (casting pins, cores, molds, etc.) are coated with a wear-resistant coating of TiC or tungsten carbide on their surfaces by chemical vapor deposition (CVD). It's starting to get worse.

In particular, tungsten carbide can be formed by CVD at a relatively low temperature of about 600°C or less, so it can be applied not only to ferrous metal parts but also to low-melting metal parts such as Af and Cu, and precision parts that are sensitive to thermal distortion. It has the advantage that it can also be applied.

As a technique for forming the above-mentioned tungsten carbide layer on the surface of metal parts, for example, Japanese Patent Application Laid-Open No. 52-89583 discloses a technique in which a nickel phosphorus plating layer is formed on the surface of a steel base material. A die mold having a tungsten carbide layer or a layer of a mixture of tungsten and tungsten carbide on its surface and a method for manufacturing the same are described.

On the other hand, the applicant of the present application proposed a method for manufacturing a wear-resistant article having a tungsten layer and a tungsten carbide layer in Japanese Patent Application No. 61-29370.

In these conventional techniques, the surface of the metal part is generally mechanically ground with a puff or the like, then nickel phosphorus plating is applied to the surface, and a tungsten carbide layer (or a tungsten layer and tungsten layer) is formed on the surface of the nickel phosphorus plating layer by chemical vapor deposition. carbide layer).

[Problem that the invention seeks to solve]

In the wear-resistant article having a tungsten carbide layer manufactured by the above-mentioned conventional technique, a nickel phosphorus plating layer 101 is formed with a thickness of several μm on the surface of a metal base material 100, as shown in FIG. A tungsten carbide layer 102 having a thickness of, for example, 10 to 20 μm is formed on the surface of N101. A microscopic observation of the structure of the surface of this wear-resistant article shows that although minute protrusions on the metal surface are generally ground smoothly by mechanical grinding, minute depressions are hardly ground by mechanical grinding, and many sharp edges are formed. There are parts left. Therefore, when stress or impact is applied during use of the wear-resistant article, cracks occur in the tungsten carbide layer 102 from the edge portions, and the tungsten carbide layer 102 begins to peel off from the cracks.
There is a problem that the durability of the tungsten carbide layer 102, that is, the durability of the wear-resistant article decreases.

[Means for solving problems]

The method of manufacturing a wear-resistant article having a tungsten carbide layer according to the present invention includes mechanically grinding the metal surface of a fully bent part, electrolytically polishing the metal surface, and depositing tungsten carbide on the metal surface by chemical vapor deposition. It forms a layer.

[Effect]

In the method of manufacturing a wear-resistant article having a tungsten carbide layer according to the present invention, first, the metal surface of the metal component is mechanically ground, and this mechanical grinding polishes relatively large protrusions and edges on the metal surface. The metal surface becomes generally smooth. Next, when the metal surface is subjected to electrolytic polishing, the sharp edges remaining in the recesses of the metal surface that were not ground by mechanical grinding are polished away, and the entire surface of the metal surface becomes smooth. In this way, the tungsten carbide layer is formed on the metal surface after the metal surface is sufficiently smoothed by mechanical grinding and electrolytic polishing, making it difficult for cranks to form on the tungsten carbide layer and increasing the durability of the tungsten carbide layer. Improves removability and durability. In addition, since electrolytic polishing is performed after mechanical grinding to achieve a generally smooth surface, the processing time for electrolytic polishing may be relatively short.

〔Effect of the invention〕

According to the method for manufacturing a wear-resistant article having a tungsten carbide layer according to the present invention, as explained above, the surface of the metal part is mechanically ground and then electrolytically polished to eliminate edges from the surface of the metal part, Since a tungsten carbide layer is formed on the smooth metal surface without edges,
A tungsten carbide layer with excellent peeling resistance can be formed, and a wear-resistant article with excellent durability can be manufactured.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, a wear-resistant layer consisting of a tungsten layer and a tungsten carbide layer is formed on the inner peripheral surface of a cylindrical hole of a cylindrical metal part P (see Fig. 2) whose metal base material is, for example, alloy tool steel (SKDII). This is an example of manufacturing a wear-resistant article having the following characteristics.

In the first step, the entire surface of the metal part P, including the inner circumferential surface of the cylindrical hole, is mechanically ground using a puff to smooth the metal surface. When mechanical grinding is performed in this manner, large edges (sharp protrusions) on the metal surface are reliably removed and the metal surface becomes generally smooth, but relatively small edges still remain in minute recesses. By performing the mechanical grinding described above, large edges and marks that cannot be removed by electrolytic polishing described later can be removed, and the processing time for electrolytic polishing can be shortened. After this mechanical grinding, the entire surface of the metal part P is cleaned and degreased.

In the second step, the metal part P is electrolytically polished,
As a result, edges on the entire surface of the metal part P are removed and smoothed.

In this case, for example, an electrolytic polishing apparatus E as shown in FIG. 1 is used. This electrolytic polishing treatment apparatus E is provided with a cooling water tank 2 outside the polishing tank 1, an electric heater 3, a stirrer 4, a thermometer 5, and a cathode plate 6 inside the polishing tank 1. A metal part P is suspended, the following polishing electrolyte is stored in the polishing tank 1, the "-" terminal of the DC power supply 7 is connected to the cathode plate 6, and the "+" terminal is connected to the variable resistor 8.
and is connected to the metal part P via an ammeter 9.

When treating iron-based metal parts P, the polishing electrolyte is used in a predetermined amount consisting of, for example, 50 cc of sulfuric acid, 5 g of ferric hydroxide, 1 g of ferrous sulfate, and 0.5 g of potassium dichromate. electrolyte solution is used.

When carrying out the electrolytic polishing process, the heater 3 is operated and the cooling water is circulated to raise the temperature of the electrolytic solution to about 60 - 60°C.
1) While maintaining the temperature at 0°C, apply electricity from the DC power supply 7 to increase the current density between the cathode plate 6 and the metal part P to approximately 35 to 500°C.
A/d tri and process for approximately 10-20 seconds.

During the electrolytic treatment, the current density at the edge portion of the surface of the metal part P becomes high, so the edge portion is ionized and melted, and the edge portion of the entire surface of the metal part P is removed.

As mentioned above, by applying electrolytic polishing, it is possible to reliably remove minute irregularities caused by mechanical grinding (such as puff marks during puff grinding), edges and marks of concave parts that could not be polished by mechanical grinding. It is possible to completely polish even metal parts P with complicated shapes.

In addition, when processing metal parts made of aluminum alloy, an electrolytic solution consisting of, for example, 50 cc of phosphoric acid, 1 g of agar, and 0.5 g of caustic soda may be used as the polishing electrolyte.

In the third step, approximately 2 to 15
An electroless nickel phosphorus plating layer of μm thickness is formed. The technique for forming this metal layer may be a well-known nickel phosphorous plating technique that is widely used in practice, and detailed explanation thereof will be omitted here. However, instead of the nickel phosphorus plating layer, a nickel plating layer or a Ni-B plating layer may be formed.

In the fourth step, the metal part P is treated with a low-temperature CVD apparatus for forming a tungsten carbide layer, and a tungsten layer and a tungsten carbide layer are formed on the inner peripheral surface of the cylindrical hole of the metal part P.

Here, the above-mentioned low-temperature CVD apparatus will be briefly explained.

As shown in FIG. 2, this low-temperature CVD apparatus includes a retort 12 (reactor) consisting of a retort main body 10 and a heat insulating container 1 covering the outer circumference of the retort, an Ar gas supply source 13, and a WF
6 supply source 14, CbHb supply source 15, and H2 gas supply source 1
6, etc., a suction system that reduces the pressure in the processing chamber in the retort main body 10 using a vacuum pump 17, and a gas exhaust system that exhausts gas from the processing chamber, consisting of a water transport pump 18 and a gas purifier 19. At the upper, middle, and lower positions in the retort main body 10, there are shielding members 20 that hold metal parts P as objects to be processed and cover their outer peripheries.
is provided. A plurality of metal parts P are actually set in each shielding member 20, and the processing gas flows through the cylindrical hole of each metal part P. In addition, the reference numeral 21 in the figure
is a gas mixer.

When forming a tungsten layer and a tungsten carbide layer by chemical vapor deposition on the inner circumferential surface of the cylindrical hole of the metal part P using the low-temperature CVD apparatus, first, the vacuum pump 17 is used to suction the processing chamber to a pressure of about 10 to 50 T.

By reducing the pressure to rr, as much air as possible that would interfere with the gas phase reaction is removed, and the metal part P is heated to approximately 300 to 600°C by energizing the induction coil lla. Then, the valves 22 and 27 are opened to supply Ar gas from the Ar gas supply source 13 into the processing chamber little by little through the gas supply main pipe 28 and the gas supply pipe 28a, and the water transport pump 18 is operated to convert the air in the processing chamber into Ar gas. Recycle with gas.

Next, the valves 24 and 25 are opened, the bomb 29 and the heater 30 are activated, and a predetermined molar ratio of WF6 is introduced into the processing chamber.
The gas in the processing chamber is discharged little by little by the water transport pump 18 while supplying a mixed gas of Ar gas and H gas as a carrier little by little. When the supply of C6H as a carbon source and the raw material gas containing no gas is continued for about 10 minutes, a tungsten layer of about 1 μm is deposited on the inner peripheral surface of the cylindrical hole of the metal part P by vapor phase reaction. As described above, the thickness of the tungsten layer can be adjusted depending on the length of processing time.

Next, the valves 23 and 26 are also opened, and while a mixed gas of WF6 gas, Ar gas, ChHh gas, and H2 gas at a predetermined molar ratio is supplied into the processing chamber little by little, the gas in the processing chamber is gradually removed by the water pump 18. Discharge. When the supply of the mixed gas containing CbH6 gas as the carbon source is continued for about 1.5 to 2 hours, a tungsten carbide layer of about 10 to 20 μm is formed on the surface of the tungsten layer on the inner peripheral surface of the cylindrical hole of the metal part P. is deposited by a gas phase reaction. The tungsten carbide +-i includes wc, w2c, W, and C, and the thickness of the tungsten carbide layer can be adjusted depending on the length of the processing time as described above.

After forming a tungsten layer and a tungsten carbide layer in this order on the surface of the nickel phosphorus plating layer on the inner circumferential surface of the cylindrical hole of the metal part P by using the low-temperature CVD apparatus for forming a tungsten carbide layer, the retort 12 is covered. What is necessary is to remove the plate 10a and take out the metal parts P together with each shielding part 20 to the outside.

Medium hardness tungsten 5 (HVl 200) between ungsten carbide layer (HV2000-2500)
This is because the bonding force between the nickel rimming layer and the tungsten layer is strong, the bonding force between the tungsten layer and tungsten carbide is also strong, and the medium-hardness tungsten layer functions as a buffer material. This strengthens the bond between the nickel phosphorus plating layer and the tungsten carbide layer, and significantly improves the peeling resistance of tungsten carbide i when stress or impact force is applied.

Note that the tungsten layer may be omitted and a tungsten carbide layer may be formed directly on the surface of the nickel phosphorus plating layer. Further, when forming a tungsten layer and a tungsten carbide layer on the entire surface of the metal part P, the metal part P may be exposed in the processing chamber without using the shielding member 20.

The structure of the vicinity of the inner circumferential surface of the cylindrical hole of the metal component P as the wear-resistant article manufactured through the first to fourth steps described above is as shown in FIG.

The surface of the metal base material 31 of the metal part P is polished smoothly without any edges by mechanical grinding and electrolytic polishing, and a nickel phosphorus plating layer 32 is formed on the surface. A tungsten layer 33 is formed on the surface, and a tungsten carbide layer 34 is formed on the surface of the tungsten 1) 330.

In this way, nickel phosphorus plating layer 3 is applied to the smooth metal surface.
2 and tungsten N33 and tungsten carbide layer 3
4 is formed, the peeling resistance of the tungsten layer 33 and the tungsten carbide layer 34 when stress or impact is applied is significantly improved, and a wear-resistant article with excellent durability can be obtained.

Note that the shape and structure of the metal part P are not limited to those in the example, and almost all metal materials such as steel, alloy steel, aluminum alloy, aluminum, copper, etc. can be used as the metal base material of the metal part P. Targeted.

[Brief explanation of the drawing]

The drawings relate to embodiments of the present invention, and FIG. 1 is an overall configuration diagram of an electrolytic polishing processing apparatus, FIG. 2 is an overall configuration diagram of a low-temperature CVD apparatus for forming tungsten carbide, and FIG. 3 is a diagram showing essential parts of metal parts. The enlarged sectional view of FIG. 4 is a view corresponding to FIG. 3 of a metal part manufactured by the conventional technique. P...Metal parts, 34...Tungsten carbide layer. Patent applicant Mazda Motor Corporation Figure 3

Claims (1)

[Claims] (1) Wear resistance having a tungsten carbide layer, which is characterized by mechanically grinding the metal surface of a metal part, electrolytically polishing the metal surface, and forming a tungsten carbide layer on the metal surface by chemical vapor deposition. Method of manufacturing sex products.