Surface-coated member

Abstract

The present invention provides a surface-coated member in which the integrity of a coating film is maintained, and which has excellent anti-adhesion properties to a titanium alloy. The surface-coated member has a substrate and a hard film formed on the substrate. The hard film has a component composition expressed by the formula: (Zr1-xNdx)NyO1-y (in the formula, x represents the atomic ratio of Nd to the total amount of Nd and Zr, y represents the atomic ratio of N to the total amount of N and O, 0.011 < x ≤ 0.607, and 0 ≤ y ≤ 1).

Description

Surface coating member

[0001] The present invention relates to a surface coating member having excellent adhesion resistance.

[0002] Titanium alloys possess high specific strength, form a stable passive film, and exhibit excellent corrosion resistance. Therefore, titanium alloys are widely used in aircraft and ship components, among other applications. However, because titanium itself is a highly reactive metal, adhesion to mating materials is known to easily occur when processing titanium alloys.

[0003] For example, when machining a workpiece made of titanium alloy, the newly exposed surface of the titanium alloy may adhere to the cutting tool, potentially damaging the cutting edge or other parts of the tool. Alternatively, machining a workpiece made of titanium alloy may result in reduced machining accuracy. For similar reasons, sliding parts containing titanium alloy are prone to seizing with the mating material. Therefore, it is generally considered difficult to use titanium alloy as a material for sliding parts.

[0004] On the other hand, with regard to hard coatings formed on cutting tools, many attempts have been made to improve the performance of the coating by incorporating a predetermined metal element into the Zr nitride. For example, Patent Document 1 describes a chemical formula Hf that satisfies predetermined conditions. １－ａ Zr ａ X ｂ A surface-coated cutting tool is disclosed, comprising at least a zirconium-containing hafnium layer in the coating, which contains a compound having a predetermined crystal structure as shown in [the provided formula].

[0005] Furthermore, Patent Document 2 describes a material having an average layer thickness within a predetermined range, and whose compositional formula is: (Zr １－γ Y γ A surface-coated cutting tool is disclosed, in which a hard coating layer is formed on the surface of the tool substrate, consisting of a single layer of a composite nitride layer of Zr and Y satisfying N (where the atomic ratio is 0.01 ≤ γ ≤ 0.15).

[0006] Japanese Patent Publication No. 2009-148856 Japanese Patent Publication No. 2012-106297

[0007] An object of the present invention is to provide a surface-coated member that maintains the soundness of the coating and has excellent adhesion resistance to titanium alloys.

[0008] The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems.

[0009] The surface-coated member according to the first aspect of the present invention is a surface-coated member comprising a base material and a hard coating formed on the base material, wherein the hard coating is represented by the formula: (Zr １－ｘ Nd ｘ )N ｙ O １－ｙ (wherein in the formula, x represents the atomic ratio of Nd to the total amount of Nd and Zr, y represents the atomic ratio of N to the total amount of N and O, 0.011 < x ≤ 0.607, and 0 ≤ y ≤ 1).

[0010] FIG. 1 is a schematic diagram for explaining the arrangement of two target evaporation sources and a substrate in a chamber of an unbalanced magnetron sputtering apparatus in the present example. FIG. 2 is a graph showing the relationship between the atomic ratio (x) of Nd to the total amount of Zr and Nd (total amount of metal elements) and the atomic ratio (y) of N to the total amount of N and O (total amount of non-metal elements) in Examples 1-1 to 1-15 and Comparative Examples 1-1 to 1-10. FIG. 3 is a schematic diagram for explaining the arrangement of a target evaporation source and a substrate in an arc ion plating apparatus in the present example. FIG. 4 is a graph showing the relationship between the atomic ratio (x) of Nd to the total amount of Zr and Nd (total amount of metal elements) and the average friction coefficient in the evaluation of adhesion resistance to titanium alloys in Examples 2-1 to 2-12 and Comparative Examples 2-1 to 2-3.

[0011] It is described that according to the surface-coated cutting tools described in Patent Document 1 and Patent Document 2, high wear resistance, excellent heat resistance and welding resistance in high-speed cutting of difficult-to-cut materials can be obtained. However, the coatings described in any of the documents still have room for improvement from the viewpoint of adhesion resistance when processing titanium alloys having high activity.

[0012] As a result of diligent research by the inventors, it was found that a hard coating made of nitride containing zirconium (Zr) and neodymium (Nd) as metallic elements may improve the adhesion resistance to titanium alloys. However, Zr and Nd do not melt together even when the temperature is raised, and separate into two phases. Therefore, it is difficult to stably form a coating using Zr and Nd by conventional methods. In addition, Nd and nitrides of elemental Nd spontaneously oxidize in the atmosphere, and the oxide is a brittle and easily crumbled substance. Therefore, even if a coating containing Nd is formed by conventional methods, it is difficult to handle. Furthermore, as a result of further diligent research by the inventors, it was found that even if a hard coating made of nitride containing Zr and Nd could be formed, depending on the atomic ratio of Zr and Nd, there may be problems with the integrity of the coating, such as blistering and peeling.

[0013] The inventors diligently conducted experiments on surface coating members that maintain the integrity of the coating and have excellent adhesion resistance to titanium alloys, from the viewpoint of the atomic ratio of Nd to the total amount of Nd and Zr (see the examples described later). As a result, the hard coating formed on the substrate was given by formula: (Zr １－ｘ Ndx)N ｙ O １－ｙ It was found that by using a component composition represented by (wherein the formula, x represents the atomic ratio of Nd to the total amount of Nd and Zr, and y represents the atomic ratio of N to the total amount of N and O, with 0.011 < x ≤ 0.607 and 0 ≤ y ≤ 1), a surface coating member that has the effect of both film integrity and excellent adhesion resistance to titanium alloys can be obtained.

[0014] Thus, according to the present invention, it is possible to provide a surface coating member that maintains the integrity of the coating and has excellent adhesion resistance to titanium alloys.

[0015] The embodiments of the present invention will be described in detail below. However, the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without impairing the spirit of the invention.

[0016] 1. Structure of the Surface Coating Member First, the structure of the surface coating member according to this embodiment will be described. The surface coating member has a base material and a hard coating formed on the base material.

[0017] As used herein, the "member" of a surface-coated member is not particularly limited as long as it has a base material portion on which a hard film can be formed. In particular, the "member" of a surface-coated member is preferably any member known to those skilled in the art that has a base material portion requiring adhesion resistance to titanium alloys. Examples of such members include cutting tools such as end mills, drills, taps, cutting bits, dies, inserts, milling cutters and reamers, and sliding members such as bearings, blades, vanes, packings, seal rings, guides, stages, cylinders and piston members.

[0018] 1-1. Base Material As used herein, the "base material" is at least a part of the aforementioned member on which the hard film is formed, and is the main constituent part of the member. That is, the base material may be at least a part of the outer surface of the aforementioned member (i.e., the functional portion) that comes into contact with a material containing titanium alloy (for example, a workpiece containing titanium alloy) when the aforementioned member is used.

[0019] The material of the base material is not particularly limited as long as it is any material known to those skilled in the art. Examples of the material of the base material include materials such as cemented carbide, cermet, ceramic and CBN sintered compacts, and steel materials such as high-speed tool steel, die steel and stainless steel.

[0020] 1-2. Hard Film The hard film is formed on the aforementioned base material, for example, by the method described later. Hereinafter, the composition and thickness of the hard film will be described in detail.

[0021] <Composition of Hard Film> In the present embodiment, the hard film is represented by the formula: (Zr １－ｘ Nd ｘ )N ｙ O １－ｙ (wherein, in the formula, x represents the atomic ratio of Nd to the total amount of Nd and Zr, y represents the atomic ratio of N to the total amount of N and O, and 0.011 < x ≤ 0.607, and 0 ≤ y ≤ 1).

[0022] That is, the hard coating is a nitride (when y=1), an oxynitride (when 0<y<1) or an oxide (when y=0) containing Zr (zirconium) and Nd (neodymium) as metal elements.

[0023] Zr nitride is thermodynamically more stable than Ti nitride. Therefore, even when Zr nitride comes into contact with a titanium alloy, nitrogen in the Zr nitride is less likely to be abstracted by the titanium alloy, and the Zr nitride maintains a stable state. By including Nd in addition to Zr in the composition of metal elements in the coating, the adhesion resistance of the hard coating to titanium alloys can be improved.

[0024] On the other hand, Nd is an element that is easily oxidized. Therefore, (Zr １－ｘ Nd ｘ )N (wherein 0.011 < x ≤ 0.607) Even when a hard coating having the component composition represented by the formula is formed on a base material to produce a surface-coated member, if the member is left in an atmospheric atmosphere, a natural oxide film is formed on the surface of the nitride. This is due to the influence of Nd in the hard coating. Accordingly, the component composition of the hard coating has the same atomic ratio x of Nd over time, (Zr １－ｘ Nd ｘ )N ｙ O １－ｙ (wherein 0 < y < 1) an oxynitride having the component composition or (Zr １－ｘ Nd ｘ )O can be changed to an oxide of

[0025] When the atomic ratio x of Nd to the total amount of Nd and Zr (total amount of metal elements) in the above formula is more than 0.011, a hard coating having excellent adhesion resistance to titanium alloys can be obtained.

[0026] The atomic ratio x of Nd to the total amount of Nd and Zr (total amount of metal elements) is preferably 0.100 ≤ x, more preferably 0.109 ≤ x, and still more preferably 0.132 ≤ x. Further, the atomic ratio x of Nd to the total amount of Nd and Zr (total amount of metal elements) is particularly preferably not less than a value selected from the group consisting of 0.151, 0.214, 0.275, 0.303, 0.309, and 0.335.

[0027] If the atomic ratio x of Nd to the total amount of Nd and Zr (total amount of metal elements) in the above formula is 0.607 or less, the integrity of the coating can be maintained even when the surface coating member having the hard coating is left in an atmospheric environment. In detail, as mentioned above, (Zr １－ｘ Nd ｘ A hard nitride film of N (wherein 0.011 < x ≤ 0.607) will, over time, have the same Nd atomic ratio x value (Zr) due to the influence of Nd in the film. １－ｘ Nd ｘ ) N ｙ O １－ｙ (wherein the formula, 0 < y < 1) oxynitride or (Zr １－ｘ Nd ｘ ) may change into a hard oxide film of O. However, even if the hard film changes in this way, if the atomic ratio x of Nd is 0.607 or less, macroscopic defects such as blistering and peeling will not occur in the film.

[0028] In this specification, "maintaining the integrity of the coating" means, for example, that when the appearance of the hard coating is observed visually and the observed area is examined with a scanning electron microscope at a magnification of 2000x, no defects such as blistering or peeling are observed on the appearance of the coating.

[0029] The atomic ratio x of Nd to the total amount of Nd and Zr (total amount of metal elements) is preferably x ≤ 0.600, more preferably x ≤ 0.586, and even more preferably x ≤ 0.551. Furthermore, it is particularly preferable that the atomic ratio x of Nd is less than or equal to a value selected from the group consisting of 0.500, 0.457, 0.430, and 0.400.

[0030] In this specification, the atomic ratio of Nd or Zr to the total amount of Nd and Zr (more specifically, the total amount of metallic elements) and the atomic ratio of N or O to the total amount of N and O (more specifically, the total amount of nonmetallic elements) in a hard coating can be measured, for example, by energy-dispersive X-ray spectroscopy (EDS analysis) mounted on a scanning electron microscope energy-dispersive X-ray spectrometer.

[0031] The composition of the hard coating may include, in addition to the elements Zr (zirconium), Nd (neodymium), N (nitrogen), and O (oxygen) described above, unavoidable impurities such as metallic elements, nonmetallic elements, and metalloid elements, as long as they do not impair the integrity of the coating and its excellent resistance to adhesion to titanium alloys in this embodiment. For example, when the hard coating is formed by sputtering, the hard coating may contain unavoidable impurities such as Ar (argon).

[0032] <Thickness of the hard coating> The thickness of the hard coating is not particularly limited as long as it does not impair the integrity of the coating and the excellent adhesion resistance to titanium alloys of this embodiment. For example, the thickness of the hard coating is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and particularly preferably a value selected from the group consisting of 0.2 μm, 0.5 μm, 0.7 μm, and 1 μm or more. When the thickness of the hard coating is 0.01 μm or more, crystallization of the hard coating becomes possible, and a surface coating member with even better adhesion resistance to titanium alloys can be obtained.

[0033] The upper limit of the hard coating thickness is not particularly limited. For example, from the viewpoint of cost and productivity, the hard coating thickness is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less.

[0034] The surface-coated member according to this embodiment has a base material and a hard coating formed on the base material, thus maintaining the integrity of the coating and exhibiting excellent resistance to adhesion to titanium alloys. Therefore, the surface-coated member can be suitably used, for example, as a cutting tool for workpieces made of titanium alloys or as a sliding member that comes into contact with parts made of titanium alloys.

[0035] 2. Other Configurations of the Surface Coating Member The surface coating member according to this embodiment may, if necessary, have an underlayer between it and the hard coating, for example, to further improve the adhesion between the substrate and the hard coating, as long as it does not impair the soundness of the coating and the excellent resistance to adhesion to titanium alloys of this embodiment. The underlayer can be formed from, for example, one or more layers of metal, nitride, carbonitride, and carbide.

[0036] Furthermore, as long as the integrity of the coating in this embodiment and the excellent anti-adhesion properties to titanium alloys are not impaired, the surface coating member may have an upper layer formed on top of the hard coating formed on the substrate, having a composition and / or composition ratio that does not satisfy the conditions of the component composition of the hard coating in this embodiment described above.

[0037] Furthermore, the surface coating member may have another hard coating (hereinafter referred to as the "second hard coating") formed on top of a hard coating formed on the substrate (hereinafter referred to as the "first hard coating"), which has a different composition and / or composition ratio from the first hard coating but satisfies the component composition conditions of the hard coating in this embodiment described above. Furthermore, the surface coating member may have yet another hard coating (hereinafter referred to as the "third hard coating") formed on top of the laminated coatings, which satisfies the component composition conditions of the hard coating in this embodiment described above.

[0038] Alternatively, the surface coating member may have a first hard film and a second hard film (or a first hard film, a second hard film, and a third hard film) laminated together. Furthermore, the surface coating member may have two or more layers of the first hard film and the second hard film (or a first hard film, a second hard film, and a third hard film) alternately laminated together. Alternatively, as long as the integrity of the coating and the excellent adhesion resistance to titanium alloys of the surface coating member in this embodiment are not impaired, the surface coating member may have one or more layers of hard films containing nitrides, carbonitrides, oxides, or oxynitrides of metallic elements that do not satisfy the component composition conditions of the hard film in this embodiment, metals, nitrides, carbonitrides, and carbides sandwiched between the laminated hard film structures that satisfy the component composition conditions of the hard film in this embodiment described above.

[0039] When one or more underlayers, top layers, and / or different hard coatings are formed on the substrate of the surface coating member, the total thickness of the laminate is preferably 10 μm or less, and more preferably 8 μm or less, although this is not particularly limited.

[0040] 3. Method for Manufacturing Surface-Coated Members The surface-coated members according to this embodiment can be manufactured by applying any vacuum deposition method known to those skilled in the art to form (coat) a hard film on a substrate. Specifically, arc ion plating, sputtering, etc., can be applied to coat the hard film. As an example, the method for manufacturing a surface-coated member using arc ion plating will be described below.

[0041] A film deposition apparatus used in arc ion plating includes, for example, an arc evaporation source equipped with a target made of hard film material, an anode to which electrons enter during arc discharge, an arc power supply for supplying arc current to the target, a chamber (vacuum vessel) for housing the substrate, a substrate rotation mechanism for rotating the substrate in the chamber, a bias power supply for applying a bias voltage to the substrate, a heater for heating the chamber and the substrate, a vacuum pump for creating a vacuum in the chamber, and a gas inlet for introducing either or both an inert gas (argon, helium, neon, krypton, etc.) and a reaction gas (nitrogen gas) into the chamber. The film deposition apparatus may also include a filter mechanism that can reduce droplets, which are clumps of film-forming material, using a magnetic field.

[0042] In the manufacturing method of the surface coating member according to this embodiment, the target is Zr １－ｘ Nd ｘ (However, it is not particularly limited as long as it is possible to form a film having a metal component composition of 0.011 < x ≤ 0.607.) Specifically, a target consisting of Zr and Nd having a predetermined composition may be used.

[0043] In the arc ion plating method for film deposition, the chamber is first evacuated. At this time, the vacuum pressure is 10 × 10－３ It is preferable to keep the pressure below Pa. By using a vacuum, oxidation of the substrate can be prevented by starting the heating of the substrate while there is a large amount of residual gas in the chamber.

[0044] After vacuuming, the substrate is heated. The heating temperature is preferably 300°C to 650°C at the workpiece temperature. Heating the substrate within this temperature range prevents a decrease in film adhesion due to insufficient diffusion at the substrate-film interface caused by excessively low temperatures. Furthermore, it also prevents the substrate material from softening due to heat.

[0045] Next, the substrate is etched. The etching process can be carried out by introducing an inert gas into the chamber, plasma-generating the inert gas, and causing the inert gas ions to collide with the substrate to which a negative bias voltage has been applied. Alternatively, the mounted arc evaporation source can be discharged together with the inert gas as desired, ionizing a target having a predetermined metal composition (for example, a target made of Ti or Cr) attached to the arc evaporation source, and the inert gas as desired, and causing these to collide with the substrate to carry out the etching process. If the arc evaporation source is discharged without using an inert gas, the etching process can be carried out using only metal ions.

[0046] During etching, a negative bias voltage is applied to the substrate. From the viewpoint of obtaining a sufficient etching effect, the applied voltage is preferably between -100V and -1000V. If the bias voltage applied to the substrate is too low, a sufficient etching effect may not be obtained. On the other hand, if the voltage is too high, abnormal discharge may occur on the substrate surface, potentially damaging the substrate.

[0047] After etching, a hard film is deposited on the substrate. Nitrogen gas is introduced into the chamber during film deposition. To stabilize the discharge, an inert gas may be mixed with the nitrogen gas.

[0048] To form a dense, high-strength hard film containing nitrides, the pressure inside the chamber during film formation is preferably 0.5 Pa to 6 Pa. If the pressure is too low, the reaction between the evaporated metal and nitrogen gas may be insufficient, and the desired nitride may not be formed. On the other hand, if the pressure is too high, the evaporated metal ions may collide with the reaction gas, causing these ions to reach the substrate in an energy-lost state. As a result, these ions may not be able to diffuse sufficiently on the substrate surface, preventing the formation of a dense film and potentially leading to a decrease in film strength.

[0049] The bias voltage applied to the substrate is preferably -15V to -300V. The arc current supplied to the target is preferably 50A to 200A.

[0050] By going through this method, ultimately, (Zr １－ｘ Nd ｘ A hard coating having a component composition represented by )N (wherein 0.011 < x ≤ 0.607) is formed on a substrate, and a surface coating member according to this embodiment can be manufactured.

[0051] Furthermore, as mentioned above, when the surface coating material manufactured in this way is taken out into the atmosphere and left in that atmospheric environment, a native oxide film is formed on the surface of the nitride due to the influence of Nd in the hard coating. Therefore, the (Zr) formed as nitride １－ｘ Nd ｘ A hard coating having a component composition represented by )N (wherein 0.011 < x ≤ 0.607 in the formula) will have the same atomic ratio x of Nd over time (Zr １－ｘ Nd ｘ ) N ｙ O １－ｙ (wherein the formula, 0 < y < 1) oxynitride or (Zr １－ｘ Nd ｘ It can change into a hard oxide film of )O.

[0052] As described above, this specification discloses various aspects of technology, the main technologies among them are summarized below.

[0053] A surface coating member according to a first aspect of the present invention is a surface coating member having a base material and a hard coating formed on the base material, wherein the hard coating is made of a material of the formula: (Zr １－ｘ Nd ｘ ) N ｙ O １－ｙ (wherein the formula, x represents the atomic ratio of Nd to the total amount of Nd and Zr, and y represents the atomic ratio of N to the total amount of N and O, with 0.011 < x ≤ 0.607 and 0 ≤ y ≤ 1) the component composition is as shown.

[0054] A surface coating member according to a second aspect of the present invention is a surface coating member according to a first aspect, wherein in the formula, 0.109 ≤ x.

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0056] In this example, an evaluation test was conducted on the integrity of the coating according to the atomic ratio x of Nd to the total amount of Nd and Zr (total amount of metal elements). Furthermore, an evaluation test was conducted on the adhesion resistance to titanium alloy according to the atomic ratio x of Nd to the total amount of Nd and Zr (total amount of metal elements).

[0057] [Evaluation Test 1: Evaluation Test of Coating Integrity According to Nd Atomic Ratio] In this Evaluation Test 1, first, several surface-coated samples were prepared in which hard coatings with an Nd composition gradient were formed by combinatorial deposition. Then, the atomic ratios of Nd and N were measured at multiple arbitrarily selected locations on the hard coatings of these samples. Finally, the integrity of the coatings at the locations where the atomic ratios were measured was evaluated.

[0058] <Method for Manufacturing Surface-Coated Samples> In this evaluation test 1, surface-coated samples with a hard film having an Nd composition gradient were manufactured using a UBMS apparatus ("UBMS202" manufactured by Kobe Steel, Ltd.) equipped with an unbalanced magnetron sputtering evaporation source.

[0059] In the chamber of the UBMS apparatus, two targets, namely a pure Zr target and a pure Nd target, and a sample consisting of a 4-inch Si wafer as the substrate were placed. Figure 1 shows a schematic diagram illustrating the arrangement of the two target evaporation sources and the substrate in the chamber of the UBMS apparatus in this embodiment. In Figure 1 and Figure 3, which will be described later, the reference numerals indicate Zr target evaporation source 1, Nd target evaporation source 2, table 3, and substrate 4, respectively. As shown in Figure 1, the Zr target evaporation source 1 and Nd target evaporation source 2 were arranged in the chamber such that there was a 90° angle difference between them. Furthermore, in order to ultimately form a hard film with a compositional gradient of Zr and Nd, the sample as the substrate was placed on table 3 in the chamber so that there was a 45° angle difference with respect to both target evaporation sources.

[0060] After positioning the target and substrate, vacuum is applied to the chamber, and the contents of the chamber are 1 x 10 －２ The pressure was set to less than Pa. Next, the chamber was heated at a heater temperature of 700°C for 30 minutes to remove residual moisture from the chamber and the sample surface. Furthermore, to remove the contaminating layer from the surfaces of the placed Zr and Nd targets, a press putter was applied at 0.5 kW for 10 minutes. Subsequently, to improve the adhesion of the sample during film formation, Ar gas was introduced, and a bombardment treatment was performed for 2 minutes under the conditions of a filament current of 5 A and a bias voltage of -500 V.

[0061] Subsequently, hard nitride films with a compositional gradient of Zr and Nd were formed on the samples to produce surface-coated samples. Specifically, combinatorial deposition was performed to form hard films with a compositional gradient by creating a nitrogen and argon atmosphere in the chamber, setting the bias voltage to -70V, and discharging a constant power between 0.25kW and 1kW to each target. By varying the power input to each target for each sample, multiple surface-coated samples with a wide range of Nd and Zr component compositions were prepared on a single surface-coated sample.

[0062] <Method for Measuring the Atomic Ratio of Nd and N> The atomic ratios of Nd and N were measured using multiple surface-coated samples prepared by the method described above. Specifically, the atomic ratios of Nd and N in the central part in the vertical direction at multiple arbitrary locations in the horizontal direction of the surface-coated sample were measured. The same measurement was performed on each surface-coated sample, and measurements were taken at a total of 25 locations out of all the prepared surface-coated samples. The measurements were performed by EDX compositional analysis using a scanning electron microscope energy-dispersive X-ray spectrometer (SEM-EDX) (SEM: Hitachi, Ltd. "S-3500N", EDX: Horiba, Ltd. "EMAX ENERGY") to measure the atomic ratio of Nd to the total amount of Zr and Nd (total amount of metallic elements) and the atomic ratio of N to the total amount of N and O (total amount of non-metallic elements) at the 25 locations. The measurement results, along with the evaluation results of the integrity of the coating described below, are summarized in Table 1 below.

[0063] <Method for Evaluating the Integrity of the Coating> The integrity of the coating was evaluated by visually inspecting the appearance of 25 locations on the film where the atomic ratios of Nd and N were measured using the method described above, and by observing them with the scanning electron microscope described above. Specifically, if defects such as blistering or peeling were observed on the appearance of the film when visually inspected and when the visually inspected location was observed with a scanning electron microscope at a magnification of 2000x, the integrity of the coating was evaluated as "failure." On the other hand, if no defects such as blistering or peeling were observed on the appearance of the film at the observed location, the integrity of the coating was evaluated as "acceptable."

[0064] The evaluation results of the integrity of the coating, along with the measurement results of the atomic ratios of Nd and N mentioned above, are summarized in Table 1 below. In Table 1 below, "UBMS" in the "Film Formation Method" column means that the hard coating was formed by the sputtering method using "UBMS202".

[0065]

[0066] Furthermore, Figure 2 shows a graph summarizing the results from Table 1 above, illustrating the relationship between the atomic ratio of Nd (x) to the total amount of Zr and Nd (total amount of metallic elements) and the atomic ratio of N (y) to the total amount of N and O (total amount of nonmetallic elements) in Examples 1-1 to 1-15 and Comparative Examples 1-1 to 1-10.

[0067] <Discussion> As shown in Examples 1-1 to 1-15 of Table 1 above, when the atomic ratio (x) of Nd to the total amount of Zr and Nd in the hard film (total amount of metal elements) was 0.607 or less, no defects were observed in the appearance of the film, and the integrity of the film was maintained.

[0068] Furthermore, as shown in Figure 2, in Examples 1-1 to 1-15, as the atomic ratio (x) of Nd to the total amount of Zr and Nd in the hard film (total amount of metallic elements) increased from 0.094 to 0.607, the atomic ratio of N to the total amount of N and O (total amount of non-metallic elements) decreased. This is thought to be because Nd forms a native oxide film, and as the atomic ratio x of Nd in the hard film increases, the oxidation rate increases, and the atomic ratio of O increases.

[0069] On the other hand, as shown in Comparative Examples 1-1 to 1-10 in Table 1 above, when the atomic ratio (x) of Nd to the total amount of Zr and Nd in the hard coating (total amount of metal elements) exceeded 0.607, defects such as blistering and peeling were observed on the surface of the coating, and the integrity of the coating was not maintained.

[0070] Generally, when a surface-coated sample with a hard film containing Nd is exposed to the atmosphere, a native oxide film forms on the nitride surface due to the influence of Nd in the hard film, transforming it into a hard film of oxynitride with the same Nd atomic ratio x value. However, since the Nd atomic ratio x of the hard films in Examples 1-1 to 1-15 is 0.607 or less, it is assumed that the integrity of the film was maintained. On the other hand, in the hard films of Comparative Examples 1-1 to 1-10, the Nd atomic ratio x exceeded 0.607, and the influence of native oxidation of Nd in the hard film became excessively large, which is thought to have resulted in the inability to maintain the integrity of the film and the appearance of defects in the film.

[0071] [Evaluation Test 2: Evaluation Test of Adhesion Resistance to Titanium Alloys According to the Atomic Ratio of Nd] In this Evaluation Test 2, surface-coated samples were first prepared by combinatorial deposition, on which hard coatings with a compositional gradient of Nd were formed. Surface-coated samples were also prepared on which hard coatings containing only Zr as the metallic element were formed. Subsequently, the adhesion resistance to titanium alloys according to the atomic ratio of Nd at multiple selected locations on the hard coatings of these samples was evaluated, and the atomic ratios of Nd and N at these measurement locations were measured.

[0072] <Method for manufacturing surface-coated samples>

[0073] (Manufacturing of surface-coated samples with an Nd composition gradient by sputtering method) Surface-coated samples with a hard film having an Nd composition gradient were manufactured using the same apparatus, target, and substrate as in Evaluation Test 1 described above, using the same film deposition process and conditions. Hereinafter, a hard film formed by the sputtering method using "UBMS202" will be referred to as "UBMS," as in Table 1 above, and the sample manufactured in this manner will be referred to as a "UBMS" surface-coated sample.

[0074] (Manufacturing of surface-coated samples with an Nd composition gradient by arc ion plating method) In this evaluation test 2, surface-coated samples were also manufactured separately by the arc ion plating method. Specifically, surface-coated samples with an Nd composition gradient were manufactured using an AIP apparatus (AIP-S40, manufactured by Kobe Steel, Ltd.) equipped with an arc ion plating evaporation source.

[0075] Inside the chamber of the AIP apparatus, two pure Zr targets, one pure Nd target, and four substrates were arranged. Figure 3 shows a schematic diagram illustrating the arrangement of target evaporation sources and substrates in the arc ion plating apparatus in this embodiment. Specifically, as shown in Figure 3, in order to form a hard coating with a compositional gradient of Zr and Nd, each target evaporation source was arranged on one side of the AIP apparatus from top to bottom in the order of Zr target evaporation source 1, Nd target evaporation source 2, and Zr target evaporation source 1. In addition, a sample made of cemented carbide (size: 13 mm x 5 mm) was used as the substrate 4 placed on the table 3 and attached to the three-axis rotation and revolution axis inside the apparatus.

[0076] After positioning the target and substrate as described above, vacuum is applied to the chamber, and the contents of the chamber are 1 x 10 －２ The pressure was set to less than Pa. Next, the chamber was heated at a heater temperature of 900°C for 30 minutes. Subsequently, bombardment was performed for 15 minutes under the conditions of a filament current of 40A and a bias voltage of -400V.

[0077] Subsequently, a hard nitride film having a compositional gradient of Zr and Nd was formed on the sample to produce a surface-coated sample. Specifically, combinatorial deposition was performed by discharging a hard film having a compositional gradient in the longitudinal direction within the chamber under a nitrogen atmosphere, with a bias voltage of -70V, a table rotation of 1.5rpm, and applying currents of 100A and 150A to the two Zr targets, respectively, and 100A to the Nd target. Hereinafter, the hard film formed by the arc ion plating method using "AIP-S40" will be referred to as "AIP1," and the sample produced in this manner will be referred to as the "AIP1" surface-coated sample.

[0078] (Preparation of surface-coated samples containing only Zr as a metallic element by arc ion plating) Surface-coated samples containing only Zr as a metallic element were produced by the arc ion plating method using the apparatus ("UBMS202" manufactured by Kobe Steel, Ltd.) used in the aforementioned evaluation test 1, with only an evaporation source for a pure Zr target using the arc ion plating method attached.

[0079] Specifically, after placing a sample (size: 13 mm x 5 mm) consisting of a pure Zr target and a cemented carbide base material, a vacuum is applied, and the chamber is filled to 1 x 10⁻¹⁶ －２ The pressure was set to less than Pa. Next, the chamber was heated at a heater temperature of 700°C for 30 minutes. Subsequently, bombardment was performed for 5 minutes under the conditions of a filament current of 8A and a bias voltage of -400V.

[0080] Subsequently, a hard nitride film containing Zr was formed on the sample to produce a surface-coated sample. Specifically, by discharging while the chamber was under a nitrogen atmosphere, the bias voltage was set to -70V, the table rotation speed was set to 5rpm, and the target input current was set to 150A, a surface-coated sample was obtained in which a hard film containing only Zr as the metallic element was formed on the sample. Hereinafter, the hard film formed by the arc ion plating method using "UBMS202" will be referred to as "AIP2," and the sample produced in this manner will be referred to as an "AIP2" surface-coated sample.

[0081] <Evaluation Method for Adhesion Resistance to Titanium Alloys> The adhesion resistance to titanium alloys was evaluated using multiple surface-coated samples manufactured by the three methods described above. Specifically, for the "UBMS" surface-coated sample, since the atomic ratio of Nd to the total amount of Zr and Nd (total amount of metal elements) has a gradient on the surface where the hard film is formed, a total of 12 evaluation points were arbitrarily selected from the hard film. For the "AIP1" and "AIP2" surface-coated samples, since there is no compositional distribution on the surface where the hard film is formed, a total of three surface-coated samples were used. For each of the selected points on the hard film, a sliding test was performed using titanium balls to determine the average coefficient of friction (specifically, the average coefficient of friction at a sliding distance of 0m to 3m). Finally, the adhesion resistance to titanium alloys was evaluated based on the average coefficient of friction of each point.

[0082] A sliding test was conducted using titanium balls. If the composition of the hard coating at the selected evaluation point had poor resistance to adhesion to the titanium alloy, titanium adhesion was likely to occur. When titanium adhesion occurs, the titanium balls will slide against the titanium that has adhered to the evaluation point, so it is expected that the average coefficient of friction obtained from the sliding test at the evaluation point will be high. Therefore, if the average coefficient of friction was 0.800 or less, the composition of the hard coating at the evaluation point was considered to have excellent resistance to adhesion to the titanium alloy and was evaluated as "pass". On the other hand, if the average coefficient of friction was greater than 0.800, the composition of the hard coating at the evaluation point was considered to have poor resistance to adhesion to the titanium alloy and was evaluated as "fail". Specifically, the sliding test was conducted under the following conditions.

[0083] (Sliding Test Conditions) Sliding test machine: Tribometer (CSM Corporation, "TRIBOMETER") Sliding method: Reciprocating sliding with ball on disc Ball material: φ10 pure titanium ball Amplitude distance: 10 mm Maximum sliding speed: 0.02 m / sec Load: 1 N Sliding distance: 3 m Note that when a hard coating is formed by the arc ion plating method, the surface roughness of the hard coating is greater compared to when a hard coating is formed by the sputtering method. Therefore, the two surface-coated samples formed by the arc ion plating method were subjected to wet polishing using diamond paste to adjust the surface roughness to be equivalent to that of samples formed by the sputtering method, and then the sliding test described above was performed. The evaluation results of adhesion resistance are summarized in Table 2 below, along with the measurement results of the atomic ratios of Nd and N described below.

[0084] <Method for measuring the atomic ratio of Nd and N> The atomic ratio of Nd and N was measured at a total of 15 locations where the adhesion resistance to the titanium alloy was evaluated using the method described above. Specifically, for the unslidable areas in the center of the sliding marks at the evaluation locations on the hard coating where the sliding test was performed, EDX compositional analysis was performed in the same manner as described in Evaluation Test 1 above, and the atomic ratio of Nd to the total amount of Zr and Nd (total amount of metallic elements), and the atomic ratio of N to the total amount of N and O (total amount of non-metallic elements) were measured.

[0085] The measurement results of the atomic ratios of Nd and N, along with the evaluation results of the adhesion resistance to titanium alloys mentioned above, are summarized in Table 2 below. In Table 2 below, the meaning of the classification in the "Film Formation Method" column is as described above.

[0086]

[0087] Furthermore, Figure 4 is a graph summarizing the results from Table 2 above, showing the relationship between the atomic ratio (x) of Nd to the total amount of Zr and Nd (total amount of metallic elements) in Examples 2-1 to 2-12 and Comparative Examples 2-1 to 2-3 and the average coefficient of friction in the evaluation of adhesion resistance to titanium alloys.

[0088] <Discussion> As shown in Examples 2-1 to 2-12 of Table 2 and Figure 4 above, when the atomic ratio (x) of Nd to the total amount of Zr and Nd (total amount of metal elements) in the hard coating was greater than 0.011, the average coefficient of friction in the sliding test using titanium balls was low. Therefore, it is assumed that when the atomic ratio (x) of Nd is greater than 0.011, a surface coating member with excellent adhesion resistance to titanium alloys can be obtained. Furthermore, when the atomic ratio (x) of Nd to the total amount of Zr and Nd (total amount of metal elements) in the hard coating was preferably 0.109 or higher, and more preferably 0.303 or higher, the average coefficient of friction could be kept at a generally stable low value. Therefore, it is assumed that when the atomic ratio (x) of Nd is greater than or equal to these values, a surface coating member with even better adhesion resistance to titanium alloys can be obtained.

[0089] Furthermore, as shown in Examples 2-1 to 2-12 in Table 2 and Figure 4, considering the appearance of the film, it is assumed that if the atomic ratio (x) of Nd to the total amount of Zr and Nd in the hard film (total amount of metal elements) is greater than 0.011 and less than or equal to 0.607, the integrity of the film can be maintained and a surface coating member with excellent adhesion resistance to titanium alloys can be obtained.

[0090] On the other hand, as shown in Comparative Examples 2-2 and 2-3 in Table 2 and Figure 4 above, when the atomic ratio (x) of Nd to the total amount of Zr and Nd in the hard coating (total amount of metal elements) was significantly low, or when only Zr was present as the metal element, the average coefficient of friction was high. This is presumed to be due to the adhesion of titanium.

[0091] The embodiments and examples disclosed herein should be understood in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope of the claims are intended to be equivalent.

[0092] This application is based on Japanese Patent Application No. 2025-028561, filed on 26 February 2025, and its contents are included in this application.

[0093] According to the surface coating member in the embodiment of the present invention, the integrity of the coating is maintained, and it has excellent adhesion resistance to titanium alloys. Therefore, the surface coating member can be suitably used, for example, as a cutting tool for workpieces made of titanium alloys or as a sliding member that comes into contact with parts made of titanium alloys.

Claims

1. A surface coating member having a base material and a hard coating formed on the base material, wherein the hard coating is made of a material of the formula: (Zr １－ｘ Nd ｘ ) N ｙ O １－ｙ A surface coating member having a component composition represented by (wherein x represents the atomic ratio of Nd to the total amount of Nd and Zr, and y represents the atomic ratio of N to the total amount of N and O, with 0.011 < x ≤ 0.607 and 0 ≤ y ≤ 1).

2. The surface coating member according to claim 1, wherein in the above formula, 0.109 ≤ x.

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