JPH0582472B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a cutting tool comprising a hard thin film of highly adhesive diamond-like carbon and/or diamond formed on the surface of a substrate made of a sintered alloy. The present invention also relates to a hard-coated sintered alloy suitable for wear-resistant tools and a method for producing the same.

(Conventional technology) TiC,
Sintered alloys coated with wear-resistant materials such as TiN and Al ₂ O ₃ are widely used as tools, and even today, the relationship between these wear-resistant materials as coating layers and the substrate made of sintered alloys remains unclear. Research is currently underway.

On the other hand, various methods have been proposed for producing a hard film made of diamond-like carbon or diamond, such as a CVD method, a plasma CVD method, an ion beam method, a laser beam method, an electron beam method, and an ion implantation method. Attempts have been made to coat the surface of a substrate made of sintered alloy with a hard film made of diamond-like carbon or diamond and apply it to a tool, but it is currently impractical.

(Problems to be Solved by the Invention) There are two methods for producing a hard film made of diamond-like carbon or diamond. The first method uses diamond-like carbon or diamond as an evaporation source. This is a solid phase synthesis method in which a hard film is synthesized on the substrate surface by heating and evaporating it.The second method is a solid phase synthesis method in which a hard film is synthesized on the substrate surface by thermal decomposition of hydrocarbons such as methane, butane, and benzene. This is a vapor phase synthesis method that deposits .

When a hard film made of diamond-like carbon or diamond is formed by these solid-phase synthesis methods or vapor-phase synthesis methods, carbon also precipitates simultaneously with the formation of the hard film, making it easy for soft carbon to be mixed in the hard film. For this reason, if a hard film made of diamond-like carbon or diamond is directly formed on the surface of a substrate made of a sintered alloy containing iron group metals, the carbon mixed in the hard film will react with the ferrous metals on the surface of the substrate and become trapped inside the substrate. There are problems such as solid solution diffusion and generation of free carbon inside the substrate, resulting in a decrease in the strength of the substrate, poor adhesion between the substrate and the hard film, and furthermore, a decrease in the quality of the produced hard film. be. In particular, when a hard film made of diamond-like carbon or diamond is formed on the surface of a substrate made of sintered alloy by vapor phase synthesis, the ferrous metal on the surface of the substrate is The problem is that it acts as a catalyst for the decomposition of hydrogen gas, and as a result, a large amount of soft carbon such as amorphous carbon or graphite is precipitated on the surface of the substrate, resulting in an increase in solid solution diffusion of carbon into the interior of the substrate. There is. In order to improve these problems, the surface of the base made of cemented carbide is coated with carbides, nitrides, borides, oxides, etc. of group 4a, 5a, and 6a metals as an inner layer, and then the surface of this inner layer is coated with diamond. A coated cemented carbide tool has been proposed, which is coated with C as an outer layer. However, although such an inner layer has the effect of preventing carbon generated during the diamond coating process from diffusing into the substrate, it may generate free carbon within the inner layer and the outer layer, or cause the bonding between the inner layer and the diamond layer. Since carbon is also deposited on the interface, there is a problem in that the bonding strength within each layer or the adhesion strength at the interface between the inner layer and the outer layer decreases.

The present invention solves the above-mentioned problems. Specifically, the present invention solves the above-mentioned problems.
Alternatively, amorphous carbon or soft carbon made of graphite produced in the process of forming a hard film made of diamond is made into a compound with a substance that easily reacts with carbon, so that free carbon is not generated within each layer or at the interface between the layers. The object of the present invention is to provide a hard coated sintered alloy with excellent strength within the coating layer and adhesion strength at the interface between the coating layers, and a method for manufacturing the same.

(Means for Solving the Problems) The present inventors attempted to apply it to tools by coating the surface of a substrate made of sintered alloy with a hard film made of diamond. For tools that are used under harsh conditions, such as cutting tools, it is necessary to have a considerably high adhesion strength between the base and the coating layer in order to withstand use, and it is necessary to investigate the adhesion between the base and the coating layer. As a result, the present invention was completed.

That is, the hard-coated sintered alloy of the present invention contains at least one of carbides, nitrides, and mutual solid solutions of metals of groups 4a, 5a, and 6a of the periodic table, Fe,
An inner layer made of a metal compound is formed on the surface of a substrate made of a sintered alloy containing at least one of Ni, Co, W, Mo, and Cr, and an outer layer made of diamond-like carbon and/or diamond is formed on the surface of the inner layer. In the coated sintered alloy, the inner layer is a carbide, carbonitride, carbonide, carbonitride, carbide, or carbide of a metal of group 4a, 5a, or 6a of the periodic table,
Carbonitrides and at least one of these mutual solid solutions, and non-stoichiometric non-metallic elements (hereinafter referred to as carbon, nitrogen, oxygen, and boron) of 0.7 to 0.95 mol per 1 mol of metal elements. It is a hard-coated sintered alloy consisting of a single layer or multiple layers of chemical compounds. The base body made of a sintered alloy in the hard coated sintered alloy of the present invention must be selected to have a plasticity that has enough rigidity or hardness to not cause plastic deformation under externally applied loads, and is generally used. Cemented carbide or cermet, and depending on the application, a sintered alloy similar to ceramics containing a trace amount of at least one of Fe, Ni, Co, W, Mo, and Cr may also be used. In addition, the inner layer in the hard-coated sintered alloy of the present invention may include carbides, carbonitrides, carbonates, carbonitrides, and carbonitrides of metals from groups 4a, 5a, and 6a of the periodic table.
A compound consisting of at least one of carborides, Si carbides, carbonitrides, and mutual solid solutions thereof, and moreover, this compound is a non-stoichiometric compound containing less nonmetallic elements than metallic elements. In particular, the inner layer made of a non-stoichiometric compound is desirably made of a non-stoichiometric compound in an amount of 0.7 mole or more of a non-metallic element per 1 mole of a metal element, and the thickness of the inner layer is determined by the coating that forms the outer layer. 0.1 μm to prevent carbon from the outer layer from diffusing into the inside of the substrate during the process and maintain the strength of the entire coating layer.
It is desirable to set the thickness to 10 μm. Further, the outer layer of the hard coated sintered alloy of the present invention is preferably made of diamond-like carbon and/or diamond, and has a thickness of 0.5 μm to 5 μm. The total thickness of the coating layer, which is the sum of these inner and outer layers, is preferably 1 to 10 μm, especially when applied to tools with sharp cutting edges such as drilling tools.
A thickness of 4 μm is desirable. The diamond-like carbon described here includes amorphous but also crystalline carbon to some extent, and has properties similar to diamond in terms of electrical resistance, light transmittance, hardness, etc.

When the hard-coated sintered alloy of the present invention forms an inner layer made of a non-stoichiometric compound directly on the surface of a substrate, carbon contained in the substrate diffuses into the inner layer in the process of forming the inner layer. inside the base,
For example, a brittle phase such as η phase (W ₃ Co ₃ C) due to lack of carbon may occur. Therefore, carbides of metals from groups 4a, 5a, and 6a of the periodic table, which contain almost no iron group metals such as Co and Ni in the substrate surface phase or substrate surface layer,
It is also possible to use a substrate having a B-1 type solid solution having a face-centered cubic crystal structure composed of at least two kinds of nitrides. In particular, the type and thickness of the inner layer made of a non-stoichiometric compound can be easily adjusted without deteriorating the alloy properties of the substrate, and free carbon generated when forming the outer layer on the surface of the inner layer is absorbed into the interior of the substrate. It is desirable to have an inner layer that can prevent diffusion. Therefore, a first inner layer consisting of a single layer or multiple layers of at least one of carbides, nitrides, oxides, borides, and mutual solid solutions of metals from groups 4a, 5a, and 6a of the periodic table is formed on the surface of the substrate. The periodic table is displayed on the surface of this first inner layer.
At least one of the carbides, carbonitrides, carbonates, carbonitrides, and carbides of group 4a, 5a, and 6a metals, or the carbides, carbonitrides, or mutual solid solutions of these, and is non-chemical. A second inner layer consisting of a single layer or multiple layers of a stoichiometric compound is formed, and the surface of the second inner layer is coated with diamond-like carbon and/or
Or a coated sintered alloy with an outer layer made of diamond.

The method for producing the hard-coated sintered alloy of the present invention includes a substrate made of a commercially available cemented carbide mainly composed of WC or a cermet mainly composed of TiC, or
At least one of carbides, nitrides, and mutual solid solutions of group 5a and 6a metals and Fe, Ni, Co,
Using a base made of a sintered alloy made of at least one of W, Mo, and Cr by conventional powder metallurgy, the surface of this base is pretreated by polishing and cleaning, and then Ti , Zr, Hf, V, Nb, Ta,
At least one metal or alloy of W, Mo, Cr, and Si is coated by conventional wet plating, physical vapor deposition (PVD), or chemical vapor deposition (CVD), or by coating with metals or alloys of W, Mo, Cr, and Si, or by coating with metals or alloys of W, Mo, Cr, and Si, or by coating with metals or alloys of W, Mo, Cr, and Si, or by coating with metals or alloys of W, Mo, Cr, and Si by conventional wet plating, physical vapor deposition (PVD), or chemical vapor deposition (CVD), or by coating with metals or alloys of W, Mo, Cr, and Si. At least one of non-stoichiometric compounds consisting of group metal carbides, nitrides, oxides, and borides, or non-stoichiometric compounds consisting of Si carbides and nitrides, or mutual solid solutions thereof An inner layer consisting of a single layer or multiple layers coated by physical vapor deposition or chemical vapor deposition is formed on the surface of the substrate, and an outer layer consisting of diamond-like carbon and/or diamond is formed on the surface of this inner layer. The free carbon generated when forming this outer layer is diffused into an inner layer consisting of a single layer or multiple layers of at least one of metals, alloys, or non-stoichiometric compounds, and this inner layer is made up of metal elements. The non-stoichiometric compound contains 0.7 to 0.95 moles or more of the nonmetallic element per mole. Methods for forming the outer layer on the surface of the inner layer include solid-phase synthesis in which diamond powder is heated with laser or electron beam in a vacuum, or other PVD methods (ion plating,
A solid phase synthesis method using sputtering, etc.) can be used. In addition, gas consisting of hydrocarbons such as methane and hydrogen can be discharged by high frequency or microwave.
A gas phase synthesis method in which thermal decomposition is performed at 300°C to 1300°C can also be used. Furthermore, a vapor phase synthesis method applying a known CVD method, plasma CVD method, or ion implantation method can also be used. In particular, if the inner layer formed on the surface of the substrate is wet-plated or
It is preferable to use a metal or an alloy produced by the PVD method, since this makes it difficult for carbon and nitrogen on the surface of the substrate to diffuse into the inner layer during the inner layer coating process.

In the method for producing a hard-coated sintered alloy of the present invention, the inner layer formed on the surface of the substrate is formed by a PVD method,
Periodic table by CVD method or plasma CVD method
carbides, nitrides, oxides of group 4a, 5a and 6a metals;
The first inner layer is coated with a single layer or multiple layers of at least one of boride and a mutual solid solution thereof, and the surface of the first inner layer is coated with a wet plating method or the like.
Ti, Zr, Hf, V, Nb, formed by PVD method
Ta, W, Mo, Cr, Si metals or alloys and
Non-stoichiometric compounds of carbides, nitrides, oxides, and borides of metals from groups 4a, 5a, and 6a of the periodic table formed by PVD, CVD, or plasma CVD, or carbides of Si; A second layer consisting of a single layer or multiple layers consisting of a non-stoichiometric compound consisting of a nitride or at least one of these mutual solid solutions.
The second inner layer is coated with an outer layer by solid phase synthesis or gas phase synthesis. In this way, the inner layer consisting of the first inner layer and the second inner layer is
When forming the inner layer, it is easy to prevent carbon and nitrogen on the surface of the substrate from diffusing into the inner layer, and moreover, free carbon generated when forming the outer layer diffuses into solid solution within the inner layer and diffuses into the inside of the substrate. This is desirable because it prevents

(Function) The hard-coated sintered alloy of the present invention is a coated sintered alloy with excellent wear resistance because the outer layer of diamond-like carbon and/or diamond is formed as a high-quality hard thin film with excellent hardness. It is. In addition, the outer layer made of a hard thin film has strong adhesion at the boundary between the outer layer and the inner layer by diffusing and dissolving free carbon generated in the process of forming the outer layer in the inner layer. The outer layer is a coated sintered alloy with excellent peeling resistance. moreover,
The inner layer has excellent wettability and reactivity with the iron group metals contained in the substrate, so it has strong adhesion at the boundary between the inner layer and the substrate, and the inner layer has excellent peeling resistance. It has become a sintered alloy. In particular, when the inner layer is composed of a first inner layer and a second inner layer, when the inner layer is formed, there is less variation in carbon and nitrogen on the surface of the substrate, and the peeling resistance improves the adhesion between the inner layer and the substrate. It has become an excellent coated sintered alloy.

(Example) Example 1 A sintered alloy with a composition of 90% WC, 5% TiC, 5% Co (by weight) was prepared as a base in the shape of CIS standard SNG432, and the surface of this SNG432 was treated with detergent, organic solvent, etc.
After thoroughly washing with acid, alkali, water, etc., and drying, it was set in an ion plating apparatus. After the inside of this apparatus was evacuated to 0.001 Pa, the substrate was gradually heated to 600° C. while maintaining the degree of vacuum in the furnace at 0.013 Pa. Next, the substrate surface was bombarded with high-purity argon gas for 40 minutes.
Afterwards, the metal tantalum is evaporated onto the substrate surface.
Coated with Ta. The deposition rate of the Ta coating layer at this time was 6×10 ^-4 μm/sec, and the thickness of the Ta coating layer was about 2 μm. The substrate with this Ta coating layer attached was set in a plasma CVD equipment, and a microwave of 2450MHz, an output of 300W, and an internal pressure of 6700Pa were applied.
The substrate was heated to 900°C and reacted for 5 hours under the conditions of 200ml/min H ₂ and 3ml/min CH ₄ to form a film with a diameter of approximately 2μm.
Covered with a thick diamond hard layer. The hard coated sintered alloy (1) of the present invention produced in this way is
As a result of microscopic observation and X-ray analysis, it was confirmed that the inner layer was TaC _0.7 and the outer layer was a layer containing a large amount of diamond.

As a comparative example, when tantalum metal is evaporated under the conditions of Example 1, the partial pressure of acetylene gas is
A comparative product (1) having an inner layer of TaC and an outer layer containing a large amount of diamond was produced by using a 0.10 Pa atmosphere and using the same conditions as in Example 1.

Using the hard-coated sintered alloy (1) of the present invention and the comparative product (1), the cutting speed was 890 m/min using Al alloy as the work material.
As a result of conducting a turning test under the conditions of min. In case 1), the coating layer peeled off after 100 minutes of cutting.

Example 2 WC72%, TiC10%, TaC10% as the base,
CIS standard for sintered alloy with Co8% (wt%) composition
A SNG432 was prepared in the shape of SNG432, and the surface of this SNG432 was washed and dried in the same manner as in Example 1, and then set in an ion plating apparatus. Then, as in Example 1, the furnace was emptied and the substrate was bombarded with high purity argon gas while being maintained at 500°C. Afterwards, while evaporating the titanium metal, the inside of the furnace is heated with a partial pressure of nitrogen gas.
After keeping the pressure at 0.05Pa for 5 minutes, exhaust the nitrogen gas and evaporate the titanium metal in a vacuum for 5 minutes.
The inner layer was coated on the surface of the substrate by repeating evaporation of metallic titanium in an atmosphere with a nitrogen gas partial pressure of 0.05 Pa and a vacuum atmosphere. This inner layer was found to be TiN _0.6 as determined by X-ray diffraction, and the surface of the inner layer was coated with an outer layer containing a large amount of diamond with a thickness of about 2 μm in the same manner as in Example 1 of the substrate to which this inner layer was attached. Hard coated sintered alloy of the present invention produced in this way (2)
As a result of microscopic observation and X-ray diffraction, the inner layer is 2 μm.
The thickness of Ti (N _0.6 C _0.4 ) was _0.95 , and it was confirmed that the outer layer contained a large amount of diamond.

As a comparison product, the inner layer is TiN and the outer layer is diamond by continuing the atmosphere of nitrogen gas partial pressure of 0.13 Pa when evaporating the metal titanium under the conditions of Example 2, and keeping the other conditions the same as Example 2. A comparative product (2) consisting of a layer containing a large amount of

Using the hard coated sintered alloy (2) of the present invention and the comparative product (2), an Al alloy turning test was conducted under the same conditions as in Example 1. As a result, the hard coated sintered alloy (2) of the present invention teeth
The comparison product showed normal wear even after 250 minutes of cutting.
In case (2), the coating layer peeled off after 110 minutes of cutting.

Example 3 WC74%, TiC _0.7 N _0.3 10%, TaC10 as substrate
%, Co6% (wt%) composition sintered alloy according to CIS standard
A SFCN3Z shape was prepared, and the surface of this SFCN53Z was washed and dried in the same manner as in Example 1, and then set in an ion plating apparatus. The inside of this apparatus was evacuated, the substrate was gradually heated to 500°C, the surface of the substrate was bombarded with argon gas for 20 minutes, and then 10% CH ₄ was added as a reaction gas while evaporating metallic titanium.
TiC _0.3 N _0.7 was formed as the first inner layer in an atmosphere of −90% N ₂ with a gas partial pressure of 0.10 Pa, and then the reaction gas was evacuated once and then treated under the same conditions as in Example 2.
A second inner layer of TiN _0.6 and a diamond rich outer layer were coated. As a result of microscopic observation and X-ray diffraction, the hard coated sintered alloy (3) of the present invention produced in this way shows that the first inner layer is made of TiC 0.3 N 0.7 with a thickness of about 1 μm, and the second inner layer is made of TiC _0.3 N _0.7 with a thickness of about 1 μm. Ti(N _0.6 , C _0.4 ) is _0.95 ,
It was confirmed that the outer layer was a layer containing a large amount of diamonds with a diameter of approximately 2 μm.

As a comparison product, an inner layer was prepared under the same conditions as the first inner layer under the conditions of Example 3, and then Example 1 was applied to the surface of the inner layer.
A comparative product (3) with an outer layer made of diamond was fabricated in the same manner as above.

Using the hard coated sintered alloy (3) of the present invention and the comparative product (3), the cutting speed was
As a result of a milling test conducted under the conditions of 500 m/min and feed rate of 0.2 mm/blade, the hard coated sintered alloy of the present invention
In the case of (3), none of the four pieces had peeled off, whereas in the comparative product, three out of four pieces had peeled off and had reached the end of their service life.

Example 4 Micron drill made of ultra-hard alloy equivalent to CIS standard K10 (helix angle 30°, tip angle 120°, cutting edge diameter)
0.50φmm) was used as a substrate, and this substrate was set in an ion plating apparatus. The inside of this apparatus was treated in the same manner as in Example 1, with a substrate temperature of 600°C and a nitrogen gas partial pressure of 0.10 Pa. After evaporating the metal tantalum to form a first inner layer, the nitrogen gas was evacuated and a vacuum of 0.013 Pa was created. A second inner layer was formed by evaporating the tantalum metal, and then an outer layer was coated as in Example 1. As a result of microscopic observation and X-ray diffraction, this hard coated sintered alloy (4) of the present invention has a first inner layer of TaN with a thickness of 1 μm.
It was confirmed that the second inner layer was 1 μm thick and made of TaG _0.8 , and the outer layer was 1.5 μm thick and contained a large amount of diamond.

As a comparative product, a comparative product (4) consisting of a 1 μm thick TaN and diamond-rich outer layer obtained by omitting the process of forming the second inner layer was produced using the same substrate.

Using the hard coated sintered alloy (4) of the present invention and the comparative product (4), the cutting speed was
As a result of a drilling test under the conditions of 250 m/min and feed rate of 0.05 mm/rev, the hard coated sintered alloy (4) of the present invention was able to drill 75,000 holes, while the comparative product (4) was able to drill 7,000 holes. After drilling individual holes, peeling occurred and the product life was reached.

(Effects of the Invention) As a result of the above, the hard coated sintered alloy of the present invention has excellent wear resistance and peeling resistance, so it can be used in applications where a certain degree of impact force is applied, such as turning tools as well as milling tools. Industrial cutting tools including drilling tools such as tools, end mills, drills, and micron drills for semiconductor substrates, as well as wear-resistant tools including pin tips of printing pins and slitters for cutting paper, tape, etc. It is a useful material.

Claims (1)

[Claims] 1. At least one of carbides, nitrides, and mutual solid solutions of metals of groups 4a, 5a, and 6a of the periodic table, and at least one of Fe, Ni, Co, W, Mo, and Cr. A coated sintered alloy is formed by forming an inner layer made of a metal compound on the surface of a substrate made of a sintered alloy containing seeds, and an outer layer made of diamond-like carbon and/or diamond on the surface of the inner layer, wherein the inner layer is formed according to the periodic table. At least one of the carbides, carbonitrides, carbonates, carbonitrides, and carbides of group 4a, 5a, and 6a metals, the carbides and carbonitrides of Si, or mutual solid solutions thereof, and the metal Nonmetallic elements (hereinafter referred to as carbon, nitrogen, oxygen,
A hard-coated sintered alloy characterized in that it is a single layer or multilayer consisting of 0.7 to 0.95 moles of a non-stoichiometric compound (representing boron). 2. The hard coated sintered alloy according to claim 1, wherein the outer layer has a thickness of 0.5 μm to 5 μm. 3. A sintered alloy containing at least one of carbides, nitrides, and mutual solid solutions of metals from groups 4a, 5a, and 6a of the periodic table and at least one of Fe, Ni, Co, W, Mo, and Cr. A coated sintered alloy comprising an inner layer made of a metal compound on the surface of a substrate, and an outer layer made of diamond-like carbon and/or diamond formed on the surface of the inner layer, the first inner layer on the side where the inner layer is adjacent to the substrate. and a second inner layer adjacent to the outer layer, and the first inner layer is based on the periodic table.
carbides, nitrides, oxides of group 4a, 5a and 6a metals;
A single layer or a multilayer of at least one of borides and mutual solid solutions thereof, and the second inner layer is a carbide, carbonitride, or a metal of group 4a, 5a, or 6a of the periodic table.
At least one type of carbonate, carbonitride oxide, carbonoboride, carbide of Si, carbonitride, or mutual solid solution thereof, and 0.7 to 0.95 mole of nonmetallic element per mole of metal element. A hard coated sintered alloy characterized by being a single layer or multilayer consisting of non-stoichiometric compounds. 4. The hard coated sintered alloy according to claim 3, wherein the outer layer has a thickness of 0.5 μm to 5 μm. 5. A sintered alloy containing at least one of carbides, nitrides, and mutual solid solutions of metals from groups 4a, 5a, and 6a of the periodic table and at least one of Fe, Ni, Co, W, Mo, and Cr. Ti on the surface of the substrate consisting of
Non-stoichiometric metals or alloys of Zr, Hf, V, Nb, Ta, W, Mo, Cr, Si, and carbides, nitrides, oxides, and borides of metals from groups 4a, 5a, and 6a of the periodic table. A step of coating an inner layer consisting of a single layer or multiple layers of at least one of a compound or a non-stoichiometric compound of Si carbide or nitride, or a mutual solid solution thereof, and coating the surface of the inner layer with diamond-like carbon and /or A method for manufacturing a coated sintered alloy by coating an outer layer made of diamond, wherein carbon is diffused into the inner layer in the step of coating the outer layer, and the inner layer is made of a nonmetallic element per mole of the metal element. A method for producing a hard coated sintered alloy, characterized in that the amount of a non-stoichiometric compound is 0.7 to 0.95 mol. 6. A sintered alloy containing at least one of carbides, nitrides, and mutual solid solutions of metals of groups 4a, 5a, and 6a of the periodic table and at least one of Fe, Ni, Co, W, Mo, and Cr. carbides, nitrides, and oxides of metals from groups 4a, 5a, and 6a of the periodic table on the surface of a substrate consisting of
A step of coating a first inner layer consisting of a single layer or multiple layers of at least one of boride and a mutual solid solution thereof, and coating the surface of the first inner layer with Ti, Zr, Hf, V,
Metals or alloys of Nb, Ta, W, Mo, Cr, Si, carbides and nitrides of metals of groups 4a, 5a, and 6a of the periodic table,
Non-stoichiometric compounds consisting of oxides, borides, or Si
coating a second inner layer consisting of a single layer or multiple layers of at least one of non-stoichiometric compounds of carbides and nitrides, or mutual solid solutions thereof; and a step of coating diamond-like carbon on the surface of the second inner layer. and/or a method for producing a coated sintered alloy by coating an outer layer made of diamond, wherein carbon is diffused into the second inner layer during the step of coating the outer layer, and the second inner layer is coated with 1 mol of a metal element. 1. A method for producing a hard coated sintered alloy, which comprises forming a non-stoichiometric compound containing 0.7 to 0.95 moles of a nonmetallic element.