JPH0234733B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a surface-coated superhard alloy for cutting and wear-resistant parts having a thin coating layer with excellent wear resistance. Conventionally, in order to improve the wear resistance of superhard alloys, periodic materials such as titanium carbide (TiC) and titanium nitride (TiN), which are more wear resistant than the base metal, were added to the surface of the superhard alloys.
Coating with a single layer or multiple layers of various carbides, nitrides, and carbonitrides of group 4a, 5a, and 6a metals is well known and has been widely put into practical use as coating chips. One of the most widely used coating materials is TiC, which has superior physical properties in terms of oxidation resistance, hardness, and wear resistance compared to the cemented carbide itself. However, with advances in workpiece materials and cutting methods,
In order to achieve higher performance and longer life, cutting tools with even higher characteristics are desired and are being developed. As mentioned above, one possible countermeasure for these problems is the transition from a single-layer film to a multi-layer film. In other words, single-layer films are being used in ways that take advantage of their respective characteristics. For example, a typical example is a TiC+TiN double coating chip shown in Kokai 1983-3841. Due to its high hardness, TiC has flank wear resistance, but it has the disadvantage of poor crater resistance. Further, TiN has low hardness and therefore is inferior in flank wear resistance, but it is chemically stable, that is, has a large free energy of formation, -ΔG, and is stable against heat, so it is excellent in crater wear resistance. Therefore, in order to take advantage of the characteristics of each TiC
+TiN and Ti(C/N) have been developed and show better cutting performance than single layer films. In addition, JP-A-1987-
TiC-TiN, VC-VN, ZrC as shown in 56381
-There are methods of coating with solid solutions such as ZrN, and the same can be said of these. Furthermore, recently there has been _a demand for coating materials that are stable at high temperatures in order to improve welding resistance _. A TiC+Al ₂ O ₃ coating chip has been developed. These coating layers e.g. TiC+TiN, TiC+
Since the Al ₂ O ₃ multilayer film has different types of carbides, nitrides, and oxides laminated, there is a problem in that the adhesion between the different types of layers is poor and the film is likely to peel off and chip when being cut. Also, solid solution coating layers, e.g.
Since TiC-TiN, VC-VN solid solutions, etc. are difficult to manufacture, only single metal carbonitrides were used. These solid solution coating layers had a problem, for example, in that they could only exhibit the characteristics of Ti metal. Therefore, the present inventors determined that the coating layer should have (1) high high temperature hardness → wear resistance, (2) thermal expansion coefficient as close as possible to the chip material → peeling resistance, and (3) chemical resistance. As a result of our search focusing on high stability, large △G → welding resistance, we found that hafnium carbide (HfC) is good. Therefore, the present inventors developed solid solution coating layers (Ti, Hf)C, (Ti, Hf) that combined two metal carbides and nitrides.
We found a method to easily form N, (Ti, Hf)C/N, and succeeded in developing a unique solid solution coated cutting tool with excellent cutting performance.
As shown in No. 54872. In order to further improve the cutting performance of the solid solution coated cutting tool invented by the present inventors, for example, (Ti, Hf)C
The present inventors have discovered that cutting performance can be significantly improved by further coating the surface of a coated cutting tool with a compound containing oxygen as a solid solution, and based on this finding, the present invention has been developed. The object of the present invention is to provide wear resistance and crater resistance by coating the surface of a superhard metal with a solid solution of a titanium compound and a hafnium compound, and further coating the solid solution with a layer of a compound containing oxygen from the solid solution. Another object of the present invention is to provide a surface-coated superhard alloy comprising a double coating layer with excellent welding resistance. The present invention is divided into two steps: first, a step of forming a solid solution film of a titanium compound and a hafnium compound, and then a step of forming a compound film containing oxygen as the solid solution. As an example, (Ti, Hf)C
+(Ti, Hf)C・O double film coating will be described. A chemical vapor deposition method (CVD method), which is widely used to form carbides, nitrides, and oxides, was used to generate the double coating film of the present invention. Furthermore, this CVD method was carried out under reduced pressure in order to obtain a uniform and dense film. First, as the first step, the generation of (Ti, Hf)C is as follows:
This is explained by the reaction formula shown below. Hf＋2I ₂ →HfI ₄ ………(1) Ti＋2I ₂ →TiI ₄ ………(2) 4TiI ₄ +4HfI ₄ +C ₄ H ₁₀ → ₄ (Hf, Ti)C+ 10H ₁ +11I ₂ ………(3) (2 ), (3), TiI ₄ and HfI ₄ are produced by pouring a certain amount of iodine vapor (I ₂ ) into Ti and Hf metals heated to a certain temperature. The formation of this iodide and its composition are determined by the heating temperature of the metal, and 250°C to 350°C is optimal. This is because hafnium iodide has a high vapor pressure, HfI ₄
is always produced stably, but the resulting iodide composition varies depending on the heating temperature of the metal, and TiI ₃ and TiI ₂ , which have low vapor pressures, are produced. Therefore, to obtain TiI ₄ ,
We found that 250-350℃ is the optimum temperature, and it is necessary to stay within this temperature range. In addition, the metals (Ti, Hf) that contribute to the reaction are preferably sponge-like, and the particle size is preferably uniform. moreover,
Iodine (I ₂ ) is regulated by controlling its vapor pressure, and a certain amount is introduced into Ti and Hf to contribute to the reaction. The TiI ₄ and HfI ₄ produced in this way are reactant gases (here, hydrocarbons
C ₄ H ₁₀ ) is introduced onto a substrate heated to a predetermined temperature, and the reaction (3) occurs. The heating temperature (reaction temperature) of the substrate at that time is preferably in the range of 850°C to 1250°C. In this way, a solid solution of Ti and Hf (Hf, Ti)C is obtained. When the reaction temperature is below 850°C, (Hf, Ti)C is obtained, but a wear-resistant product is not completely produced. If the temperature is over 1250℃,
Since the liquidus temperature of the base (Wc-Co alloy) is 1270°C, the physical properties of the base itself deteriorate, which is not preferable.
The properties of (Hi, Ti)C obtained are of course influenced by the reaction temperature, reaction pressure, C ₄ H ₁₀ flow rate and I ₂ amount, but especially (Hf,
It was revealed that the composition of Ti)C is determined by the amount of _I2 supplied to Ti and Hf, and can be controlled arbitrarily by controlling the amounts of _TiI4 and _HfI4 . Next, the second step is a step of coating with hafnium titanium oxycarbide (Hf, Ti) C.O. Although the detailed mechanism of the (Hf, Ti)C.O production reaction is unknown, it is thought to be expressed by the following reaction formula. In other words, a mixed gas of CO ₂ +H ₂ may be used instead of C ₄ H ₁₀ as the reaction gas. CO ₂ +H ₂ CO+H ₂ O ………(4) HfI ₄ +TiI ₄ +2CO+H ₂ O → (Hf, Ti)C・O +2H ₁ +3I ₂ +CO ₂ ………(5) In the reaction of (4), CO ₂ The gas composition ratio of :H ₂ is well known, for example CO ₂ :H ₂ = 20:80% by volume.
That's fine. The reaction temperature is 800 to 1200, because the reaction formula (4) shifts completely to the right side at 800℃ or higher.
A range of ℃ is preferable. Further, the carbon component of hafnium titanium oxycarbide is optional depending on the reaction gas and reaction temperature. In this way, (Hf,
By coating Ti)C.O, it has excellent chemical stability at high temperatures, especially oxidation resistance and reaction resistance with the work material. In addition, in order to generate (Hf, Ti)C O by switching the reaction gas after generating (Hf, Ti)C, (Hf, Ti)
It was found that since C and (Hf, Ti)C.O are continuous, the adhesion is extremely good. (Hf,
The optimum film thickness of Ti)C.O is 0.5 to 2 μm, as described later. Example 1 Wc72-9Co-8TiC-11Tac (wt%,
(Hf, Ti)C was formed to a thickness of 5.0 μm using a cemented carbide chip alloy (P30 grade) under the following conditions. Reaction temperature: 950℃ Reaction pressure: 0.05Torr C ₄ H ₁₀ flow rate: 0.2ml/min Hf, Ti heating temperature: 300℃ Hf side I ₂ temperature: 30℃ Ti side I ₂ temperature: 25℃ Generation rate under these conditions is 1.2μm/h,
The composition of the obtained film was determined from the change in lattice constant by X-ray diffraction, and was 40HfC−60TiC.
(mol%). Furthermore, as a result of a diamond scratch test, the film did not peel off and the adhesion strength was high. Next, under the following conditions, hafnium titanium oxycarbide (Hf, Ti)C was placed on top of (Hf,Ti)C.
O was formed to a thickness of 1.0 μm. Reaction temperature: 1000℃ Reaction pressure: 0.2Torr Reaction gas: CO ₂ : H ₂ = 20:80 (volume %) Hf, Ti heating temperature: 300℃ Hf side I ₂ temperature: 30℃ Ti side I ₂ temperature: 25℃ Under these conditions, the obtained (Hf, Ti)C.O
It has been confirmed that the adhesion between (Hf, Ti)C and (Hf, Ti)C is very good. Example 2 20HfC-80TiC was added to the same cemented carbide as in Example 1.
Form 5.0μm. This method was the same as in Example 1, but in order to vary the amount of iodide produced, the I ₂ temperature on the Hf side was 27.5°C and the I ₂ temperature on the Ti side was 30°C.
After that, (Hf, Ti)C.O was added as in Example 1.
A thickness of 1.0 μm was formed. It has been confirmed that the obtained coating layer has good adhesion. Next, in order to investigate the wear resistance of the products of the present invention, cutting tests were conducted using the samples of Examples 1 and 2. For comparison, TiC and TiN coated chips were used. The results are shown in Table 1. Cutting conditions include workpiece material SCM ₃ (HS36~40), cutting speed 160
m/min, depth of cut 1.5mm, feed 0.2mm/rev.
The cutting life limit was set at the time when the average flank wear reached 0.4 mm. The results are shown in Table 1.

【table】

[Table] It was found that the cutting life of the product of the present invention was more than twice as long as that of the conventional product. Furthermore, Table 2 shows the results regarding crater wear, which is a measure of oxidation resistance. The cutting conditions at this time were the same as above, and the cutting time was 80 minutes.

[Table] The crater wear of the inventive product is 1/1 compared to the conventional product.
It can be seen that it is about 3, which is very good.
From this result, (Hf, Ti)C・O is TiC and TiN
It can be seen that this material is more stable at higher temperatures than the previous one, and reduces thermal diffusion wear between the workpiece material and the chip material. Example 3 Next, samples were prepared with various film thicknesses of hafnium titanium oxycarbide (Hf, Ti) C.O, and their wear resistance was investigated. First, 5.0μ of 20HfC−80TiC was applied to the same cemented carbide as in Example 1.
m form. This composition was under the same conditions as in Example 2, with the Hf side I ₂ temperature being 27.5°C and the Ti side I ₂ temperature being 30°C. After that, on the 20Hf-80TiC coating layer, hafnium titanium oxycarbide (Hf・Ti) C・O was applied under the same conditions as in Example 1 at 0.25, 0.5, 1, 2.0,
Six types of samples were prepared with varying film thicknesses of 2.5 and 3.0 μm. In the sample in which (Hf.Ti)C.O was formed to a thickness of 2.5 μm or more, the surface of the coating layer was highly uneven, and it was observed that coarse crystals had grown. next,
Cutting tests were conducted on these six types of samples. TiC and TiN coated chips were used as specific products. The results are shown in Table 3. Cutting conditions include cutting material SCM-3 (Hs35~40) and cutting speed.
160m/min, depth of cut 1.5mm, feed 0.2mm/rev. As for the cutting life, the average flank wear V _B is
The time to reach 0.4 mm was set as the limit.

[Table] The product of the present invention has a (Hf・Ti)C・O film thickness of 0.5~
It was found that good cutting life could be obtained within the range of 2.0 μm. It was also observed that (Hf.Ti)C.O film thicknesses of 0.25 μm, 2.5 μm, and 3.0 μm exhibited the same performance as the comparative product. (Hf・
For Ti)C・O0.25μm, (Hf・Ti)C・O
Because the coating layer is too thin, the workpiece material diffuses and there is no barrier effect, so it is thought that the double coating had no effect and only (Hf・Ti)C exhibited cutting performance. The (Hf.Ti)C coating layer is as detailed in the aforementioned Japanese Patent Publication No. 61-54872. Furthermore, (Hf・Ti)C・O2.5μ
If it is more than m, as mentioned above, the surface layer is highly uneven and the crystal grains are coarsened, so the frictional resistance of the surface increases and the strength of the coating layer itself decreases. For this reason, chipping is likely to occur during cutting, peeling of the coating layer occurs, and the cutting life is shortened. In the above, (Ti, Hf)C + (Ti, Hf)C・
The case of the coating layer of O was explained in detail as an example, but
In the case of (Ti, Hf)C.N+(Ti, Hf)C.N.O, the following conditions are suitable. <(Ti, Hf)C/N formation conditions> Reaction temperature: 950℃ Reaction pressure: 0.15Torr Reaction gas: CH ₄ : 1ml/min.N ₂ : 4ml/min. Hf, Ti heating temperature: 300℃ I ₂ temperature :30℃ The production rate under these conditions is 2.5μm/h,
Furthermore, on this first coating layer, (Ti, Hf)・C・N・
A second coating layer of O is formed under the following conditions. Reaction temperature: 920℃ Reaction pressure: 0.2Torr Reaction gas: CH ₄ : 1ml/min.CO ₂ and/or
CO: 1.0ml/min.N ₂ : 4ml/min.H ₂ : 1.0ml/
min. Hf, Ti heating temperature: 300℃ I ₂ temperature: 30℃ In addition, in the case of (Ti, Hf)N + (Ti, Hf)N・O, the reaction gas can be changed to N ₂ or NH ₃ , and
The coating layer can be obtained by using H ₂ containing H ₂ O, and also (Ti, Hf)C+(Ti,
Hf)N・O or (Ti, Hf)N+(Ti, Hf)C・O
Combinations such as the above can also be formed by switching the reaction gases. As described above, according to the present invention, the wear resistance and welding resistance of the cutting tool are improved, and the cutting life can be extended.

Claims (1)

[Claims] 1. Formed on the surface of a material made of cemented carbide or cermet from a composite solid solution of a titanium compound made of titanium carbide and/or titanium nitride and a hafnium compound made of hafnium carbide and/or hafnium nitride. 1. A surface-coated superhard alloy, characterized in that a first coating layer is provided thereon, and a second coating layer made of a compound layer containing oxygen in the composite solid solution is further provided thereon. 2. In claim 1, the first coating layer formed from the composite solid solution comprises (Ti, Hf)
A surface-coated superhard alloy characterized by being any one of C, (Ti, Hf)N, and (Ti, Hf)C/N. 3 In claim 1 or 2,
The second coating layer made of a compound layer containing oxygen in the composite solid solution includes titanium/hafnium oxycarbide (Ti, Hf) C.O, titanium/hafnium oxynitride (Ti, Hf) N.O, titanium/hafnium oxycarbide (Ti, Hf), N.O.
Hafnium oxycarbonitride (Ti, Hf)
Either C, N, or O, and the film thickness is 0.5~
A surface-coated superhard alloy characterized by a thickness of 2.0 μm.