JP5111259B2 - Surface covering member - Google Patents

Description

  The present invention relates to a surface covering member suitable for a cutting tool, a wear resistant member, or the like.

  At present, cermets containing Ti as a main component are widely used as surface coating members that require wear resistance, slidability, and fracture resistance, such as cutting tools, wear-resistant members, and sliding members.

  For example, in Patent Document 1, type I particles made of TiCN or the like (carbonitride of a transition metal of Group 5 transition metal) and Ti and other W metals including Group 4, 5, 6 metals of the periodic table are included. A cermet containing two types of hard phases of type II particles having a large amount at the core and a small amount at the periphery is disclosed.

  Moreover, in patent document 2, it consists of the 1st hard phase which consists of a core structure of a black core part and the peripheral part surrounding this, and the white 2nd hard phase which consists only of a peripheral part, A cermet having a structure in which the average particle size of the second hard phase is 2 to 8 times the average particle size is disclosed.

Furthermore, Patent Document 3 discloses a cutting tool in which a coating layer containing Ti, Al, and Si is formed on the surface of a cemented carbide substrate or a cermet substrate.
Japanese Patent Laid-Open No. 2-190438 JP 2005-292842 A JP 2004-351541 A

  However, even with the structure of the cermet as in Patent Documents 1 and 2, the wear resistance and fracture resistance are still insufficient, and the surface-coated member made of the coated cermet of Patent Document 3 has further fracture resistance. Improvement was desired. In particular, when the surface covering member provided with this cermet base is used as a cutting tool, the cutting performance may vary greatly depending on the work material such as steel or carbon steel, and a cutting tool that exhibits stable cutting performance. Was demanded.

  The present invention is to solve the above problems, and an object of the present invention is to provide a surface covering member having high wear resistance and fracture resistance on the surface of a cermet substrate.

The surface covering member of the present invention comprises a cermet substrate in which a hard phase composed of a nitride or carbonitride of a periodic table 4, 5 and 6 metal having Ti as a main component is bonded with a binder phase having Co or Ni as a main component. And a coating layer covering the surface of the cermet substrate, and when the cross-sectional structure of the cermet substrate is observed, the hard phase is composed of a first hard phase mainly composed of TiCN and a periodic table. consists of a second hard phase of the complex carbonitride solid solution of at least one of Ti 4, 5 and 6 metals in the surface region of the cermet substrate, the average particle size of the first hard phase a _s and then, when the average particle diameter of the second hard phase was _{b s,} a ratio between _{a s} and _{b s (b s / a s} ) is 2 to 10, wherein with respect to the entire hard phase in the surface region the average area of the first hard phase occupies a _s And then, when the average area of the second hard phase occupies was _{B s,} with a ratio between _{A s} and _{B s (B s / A s} ) is 2 to 10, wherein the coating layer has a thickness of 3 a _{.5~10μm, Ti 1-a-b} -c-d Al a W b Si c M d (C x N 1-x) ( however, M is selected Nb, Mo, Ta, Hf, from Y At least one kind, 0.45 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.1, 0.01 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.1, 0 ≦ x ≦ 1). It is characterized by becoming.

  Here, in the above-described configuration, the second hard phase contains at least one of W and Nb, and at the center of the second hard phase, the content of at least one of W and Nb is large. It is desirable that the content of at least one of W and Nb is small in the outer peripheral portion.

  Moreover, it is desirable that the ratio of (total mass of W and Nb) / (total mass of the entire metal element) in the outer peripheral portion of the second hard phase is 2 to 20%.

Further, the average particle size of the first hard phase in the interior of the cermet substrate and a _i, when the average particle diameter of the second hard phase was b _i, a _i and b _i and the ratio of (b _i / a _i ) is 2 to 8, b _s is larger than b _i , and the average area occupied by the first hard phase with respect to the entire hard phase in the cermet substrate is A _i, and the second hard phase When the average area occupied by B _i is B _i , the ratio (B _i / A _i ) between A _i and B _i is 1.5 to 5, and it is desirable that the B _s is larger than B _i .

Further, it is desirable that the b _s are present in a thickness range of 30~300μm from the b _i is greater than the surface area is the surface of the cermet substrate.

According to the surface-coated member of the present invention, the average particle size a _s of the first hard phase in the surface region an average particle diameter of the second hard phase in a ratio of _{b s (b s / a s} ) is 2 to 10 There, and in the average area of _{a s} and the ratio of the average area of _{B s} of the second hard phase occupies _(B s / _{a s)} is a surface of the cermet substrate is a 2-10 first hard phase occupies, the layer thickness but in _{3.5~10μm, Ti 1-a-b} -c-d Al a W b Si c M d (C x N 1-x) ( however, M is selected Nb, Mo, Ta, Hf, from Y At least one kind, 0.45 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.1, 0.01 ≦ c ≦ 0.05, 0 ≦ d ≦ 0.1, 0 ≦ x ≦ 1). A coating layer is formed. As a result, the wear resistance is excellent, and even if the surface region is thick, the internal stress is not increased, and the wear resistance and fracture resistance are excellent.

  Here, in the above-described configuration, the second hard phase contains at least one of W and Nb, and at the center of the second hard phase, the content of at least one of W and Nb is large. The fact that the content of at least one of W and Nb is small in the outer peripheral portion, the toughness is improved in the central portion of the second hard phase and the impact resistance is increased, and the hardness is improved in the outer peripheral portion of the second hard phase. This is desirable in terms of improving plastic deformability.

  Further, (the total mass of W and Nb) / (the total mass of the entire metal element) in the outer peripheral portion of the second hard phase is 2 to 20%, which improves the thermal conductivity of the cermet and improves the thermal shock resistance. This is desirable because of improved properties.

Further, the average particle size of the first hard phase in the interior and _{a i,} when the average particle diameter of the second hard phase was _{b i,} a ratio between _{a i} and _{b i (b i / a i} ) is a 2 to 8, b _s is greater than b _i, the average area of the first hard phase occupied for the entire the hard phase in the interior and a _i, and the average area of the second hard phase occupies a B _i When the ratio of A _i to B _i (B _i / A _i ) is 1.5 to 5 and the B _s is larger than B _i , the second hard phase effectively contributes to heat propagation Thus, it is desirable in that the thermal conductivity of the cermet is improved and the thermal shock resistance of the cermet is improved.

Further, the b _s may be present in a range thickness of 30~300μm from the b _i is greater than the surface area is the surface of the cermet substrate, to enhance the thermal conductivity in the vicinity of the cermet surface thermal shock resistance of the cermet Desirable to improve.

  About an example of the cutting tool which is a suitable example of the surface coating member of this invention, about the scanning electron micrograph about the cross section containing the coating layer and cermet base | substrate of FIG. 1, and (a) surface vicinity about the cermet base | substrate of FIG. (B) A description will be given based on a scanning electron micrograph of the inside.

As shown in FIGS. 1 and 2, the cutting tool 1 of the present invention includes a cermet substrate 4 in which a hard phase 2 is bonded with a bonding phase 3, and a coating layer 5 that covers the surface of the cermet substrate 4. Further, as apparent from FIG. 2 which is a cross-sectional structure photograph of the cermet substrate 4, the hard phase 2 is composed of a black first hard phase 2 a and an off-white second hard phase 2 b, and the surface region of the cermet substrate 4. for the average particle diameter of the first hard phase 2a and _{a s,} when the average particle diameter of the second hard phase 2b was _{b s,} the ratio of _{a s} and _{b s (b s / a s} ) is 2 is 10, when the average area occupied by the first hard phase 2a to the whole hard phase 2 in the surface region and a _s, and the average area of the second hard phase 2b occupies a B _s, the ratio between a _s and B _s (B _s / A _s ) is 2 to 10.

On the other hand, the coating layer 5 has a thickness in a _{3~10μm, Ti 1-a-b} -c-d Al a W b Si c M d (C x N 1-x) ( however, M is Nb, At least one selected from Mo, Ta, Hf, and Y, 0.45 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.1, 0.01 ≦ c ≦ 0.05, 0 ≦ d ≦ 0. 1, 0 ≦ x ≦ 1).

  This combination improves the wear resistance and fracture resistance of the cutting tool 1. In particular, when used as the cutting tool 1, excellent wear resistance and fracture resistance are exhibited even when cutting not only steel but also carbon steel.

That is, if the ratio (b _s / a _s ) is smaller than 2 or the ratio (B _s / A _s ) is smaller than 2, the wear resistance of the cutting tool 1 is lowered. Conversely, if the ratio (b _s / a _s ) is greater than 10 or the ratio (B _s / A _s ) exceeds 10, the coating layer 5 is easily peeled off and the wear resistance is deteriorated. Further, if the composition of the coating layer 5 is out of the above range, the oxidation resistance at high temperature is deteriorated and the wear resistance of the cutting tool 1 is lowered, or the internal stress is increased and the fracture resistance of the cutting tool 1 is reduced. Deteriorate. Furthermore, if the thickness of the coating layer 5 is less than 3.5 μm, the wear resistance of the cutting tool 1 is poor, and conversely if the thickness of the coating layer 5 exceeds 10 μm, the coating layer 5 tends to chip and the chipping resistance decreases. To do.

  Here, the thickness of the coating layer 5 in this invention prescribes | regulates the thickness of the coating layer 5 in a cutting edge ridgeline part. Desirable compositions of the coating layer 5 are 0.45 ≦ a ≦ 0.50, 0.02 ≦ b ≦ 0.06, 0.01 ≦ c ≦ 0.03, 0.03 ≦ d ≦ 0.08, x = 0.

  The hard phase 2 is made of a nitride or carbonitride of Periodic Tables 4, 5 and 6 metals having Ti as a main component, and the binder phase 3 has a composition having Co or Ni as a main component. The first hard phase 2a has TiCN as a main component and the content ratio of the other components is 10% by mass or less, and the second hard phase 2b is composed of at least one of Group 4, 5, and 6 metals of the periodic table and Ti. The composite carbonitride solid solution.

  Here, in the above configuration, the second hard phase 2b includes at least one of W and Nb, and at the center of the second hard phase 2b, the content of at least one of W and Nb is large, and the second hard phase 2b The fact that the content of at least one of W and Nb is small in the outer peripheral portion improves the toughness and the impact resistance at the central portion of the second hard phase 2b, and the hardness at the outer peripheral portion of the second hard phase 2b. It is desirable in terms of improving the plastic deformability.

  Further, the ratio of (total mass of W and Nb) / (total mass of the entire metal element) in the outer peripheral portion of the second hard phase 2b is 2 to 20%, so that the thermal conductivity of the cermet substrate 4 is improved. Therefore, it is desirable because the thermal shock resistance is improved.

Further, the average particle diameter of the first hard phase 2a in the interior 6 of the cermet substrate 4 and _{a i,} when the average particle diameter of the second hard phase 2b was _{b i,} a ratio between _{a i} and _{b i (b i} / A _i ) is 2 to 8, b _s is larger than b _i , and the average area occupied by the first hard phase 2a with respect to the entire hard phase 2 in the interior 6 is A _i, and the second hard phase 2b occupies When the average area is B _i , the ratio (B _i / A _i ) between A _i and B _i is 1.5 to 5, and the B _s is larger than B _i , that is, the cermet substrate 4 The surface region 7 having a large average particle size of the hard phase is present on the surface of the cermet substrate, the second hard phase 2b effectively contributes to heat propagation, and the thermal conductivity of the cermet substrate 4 is improved. It is desirable in terms of improving thermal shock resistance.

  Further, the surface region 7 exists in a thickness range of 30 to 300 μm from the surface of the cermet substrate 4 in order to increase the thermal conductivity in the vicinity of the surface of the cermet substrate 4 and improve the thermal shock resistance of the cermet substrate 4. Is desirable.

  When the cross-sectional structure is observed with a scanning electron microscope, the first hard phase 2a is observed as black particles or particles having a cored structure in which a grayish white peripheral portion exists around the black core portion. The On the other hand, the second hard phase 2b is observed as grayish white particles or particles having a cored structure in which a grayish white peripheral portion exists around the white core portion. The grayish white color may appear to be a color tone close to white or may be a color tone close to gray depending on the conditions of photography.

  In addition, as shown in FIG. 3 which is a scanning electron micrograph of (a) the vicinity of the cermet substrate and (b) inside the cermet substrate according to another embodiment, on the surface of the surface region 7, There may be a pole surface region 8 having a high content ratio of the first hard phase 2a. However, in the present invention, the absence of the extreme surface region 8 is desirable in terms of strengthening the adhesion of the coating layer 5.

  Here, the total content of the nitrides or carbonitrides of the periodic tables 4, 5 and 6 metals mainly composed of Ti forming the hard phase 2 contained in the cermet substrate 4 is 70 to 96% by mass. In particular, it is preferably 85 to 95% by mass from the viewpoint of improving wear resistance. On the other hand, when the content of the binder phase 3 is 4 to 14% by mass, the balance between hardness and toughness of the substrate is excellent. Moreover, as the binder phase 3, it is desirable to contain 65% by mass or more of Co with respect to the total amount of the iron group metal in order to improve the thermal shock resistance of the cutting tool. In order to maintain good sinterability of the cermet base 4 so that the burned surface of the cermet base 4 is a smooth surface, Ni as the iron group metal is 5 to 50% by weight, particularly 10 to 35% by weight. It is desirable to make it contain in the ratio of%.

In addition, the measurement of the particle size of the hard phase 2 in this invention is measured according to the measuring method of the average particle size of the cemented carbide prescribed | regulated to CIS-019D-2005. At this time, in the case where the hard phase 2 has a cored structure, the outer edge of the peripheral part including the core part and the peripheral part is measured as one hard phase.
(Production method)
Next, the manufacturing method of the tool mentioned above is demonstrated.

  First, TiCN powder having an average particle size of 0.1 to 1.2 μm, especially 0.2 to 0.9 μm, TiN powder having an average particle size of 0.1 to 2 μm, carbide powder of other metals described above, and nitride powder Alternatively, a mixed powder obtained by mixing any one of carbonitride powders and Co powder or Ni powder is prepared.

  Further, the average particle size of the iron group metal powder, that is, Co powder or Ni powder is preferably 2 μm or less, particularly 0.05 to 1.5 μm, in order to improve the sinterability of the cermet substrate. Furthermore, it is desirable to use a solid solution powder containing Co and Ni in a predetermined ratio as the binding metal raw material powder from the viewpoint of further improving the sinterability. The average particle size of other raw material powders is preferably 0.05 to 3 μm.

  And a binder is added to this mixed powder, and it shape | molds in a predetermined shape by well-known shaping | molding methods, such as press molding, extrusion molding, and injection molding.

  Next, according to the present invention, the above-mentioned cemented carbide having a predetermined structure can be produced by firing under the following conditions. As firing conditions, (a) after raising the temperature from 1050 to 1250 ° C. at a firing temperature A of 5 to 15 ° C./min, the firing temperature A to 1275 to 1375 ° C. to a firing temperature B of 0.1 to 3 ° C. / (B) Then, the temperature is increased from 4 to 15 ° C./minute from the firing temperature B to 1500 to 1600 ° C. in an atmosphere having a nitrogen partial pressure of 30 to 2000 Pa. After firing for 0.5 to 2 hours in an atmosphere with a nitrogen partial pressure of 30 to 2500 Pa, (d) vacuuming up to 1100 ° C., and subsequent cooling is performed under an inert gas atmosphere with a nitrogen partial pressure of 30 to 2500 Pa. To do.

  According to the present invention, the cermet substrate 4 having the above-described structure can be produced by controlling the temperature rising pattern during firing and the timing of introducing a predetermined amount of inert gas.

  Then, a coating layer is formed on the surface of the cermet substrate 4. A physical vapor deposition (PVD) method such as an ion plating method or a sputtering method can be suitably applied as the coating layer forming method.

A physical vapor deposition (PVD) method such as an ion plating method or a sputtering method can be suitably applied as the coating layer forming method. The details of an example of the film forming method will be described. When the coating layer is formed by an ion plating method, metal titanium (Ti), metal aluminum (Al), metal tungsten (W), metal silicon (Si), Using metal M (M is at least one selected from Nb, Mo, Ta, Hf, and Y) independently or a composite alloy target, the metal source is evaporated by arc discharge or glow discharge. Simultaneously with the ionization, a film is formed by reacting with nitrogen (N ₂ ) gas as a nitrogen source or methane (CH ₄ ) / acetylene (C ₂ H ₂ ) gas as a carbon source.

Further, by introducing nitrogen (N ₂ ) gas and argon (Ar) gas at a rate of 1 to 10 Pa as a film forming atmosphere, the adhesion and hardness of the coating layer to the substrate are improved. In addition, when forming a coating layer by an ion plating method or a sputtering method, it is possible to produce a high hardness coating layer by controlling the crystal structure and orientation of the coating layer, and it is possible to increase the thickness of the coating layer. In addition, it is preferable to apply a bias voltage of 30 to 70 V in order to improve the adhesion to the substrate.

  TiCN powder having an average particle diameter of 0.6 μm as measured by the microtrack method, WC powder having an average particle diameter of 1.1 μm and the carbon content shown in Table 1, TiN powder having an average particle diameter of 1.5 μm, and TaC powder having an average particle diameter of 2 μm NbC powder having an average particle size of 1.5 μm, ZrC powder having an average particle size of 1.8 μm, VC powder having an average particle size of 1.0 μm, Ni powder having an average particle size of 2.4 μm, and Co having an average particle size of 1.9 μm The mixed powder prepared by adjusting the ratio of the powder shown in Table 1 was wet-mixed with isopropyl alcohol (IPA) using a stainless steel ball mill and cemented carbide ball, 3% by mass of paraffin was added and mixed, and then CNMG120408 was mixed at 200 MPa. Press molded into a tool shape.

  Using this molded body, the temperature was raised at 10 ° C./min to a firing temperature A of 1200 ° C. in a vacuum atmosphere, and then the firing temperature A from 1200 ° C. to the firing temperature B of 1350 ° C. was 0.7 ° C./min. Then, the temperature was raised from a firing temperature B of 1350 ° C. to a firing temperature C shown in Table 2 at 8 ° C./min in an atmosphere with a nitrogen partial pressure of 150 Pa. After firing in an atmosphere for 1 hour, the temperature was lowered to 1100 ° C. under the conditions shown in Table 1, and the temperature was lowered in an inert gas atmosphere with a nitrogen partial pressure of 500 Pa to produce a cermet substrate.

  The base (sintered body) was subjected to blade edge processing (Honing R) by brushing. The substrate was set in an arc ion plating apparatus and heated to 500 ° C., and then a coating layer shown in Table 1 was formed. The film forming conditions were an atmosphere of nitrogen gas and a pressure of 4 Pa, an arc current of 150 A, a bias voltage of 35 V, and a heating temperature of 500 ° C.

The obtained cutting tool was observed with a scanning electron microscope (SEM), and an image analysis was performed in a 15 μm × 15 μm region using commercially available image analysis software for each of the surface and the interior at a 5000 × magnification. Then, the presence state of the hard phase, the surface region, and the presence of the intermediate region were confirmed, and the average particle diameters thereof were measured to calculate the ratio thereof. The results are shown in Table 2. Incidentally, d _i of Table 2 is the average particle size of the entire hard phase in the interior cermet substrate.

  Further, the composition of the central portion and the outer peripheral portion of the second hard phase inside the cermet was quantified by line analysis of Auger electron spectroscopy (AES). Note that the measurement conditions of Auger electron spectroscopy (AES) were measured with an acceleration voltage of 20 KeV, a sample current of 10 nA, and a sample tilt angle of 30 degrees. And the ratio of the total content of W and Nb with respect to the total amount of periodic table 4, 5 and 6 group metal was computed. In addition, about the calculation of a ratio, the average value about five arbitrary 2nd hard phases was taken. The results are shown in Table 3. The composition of the coating layer was observed at a magnification of 500 using a scanning electron microscope (VE8800) manufactured by Keyence Corporation, and at an acceleration voltage of 15 kV using an EDAX analyzer (AMETEK EDAX-VE9800) attached to the apparatus. The composition was quantitatively analyzed by the ZAF method, which is a type of energy dispersive X-ray spectroscopy (EDX) method. For elements that could not be measured by this method, an X-ray photoelectron spectrometer (Quantum2000) manufactured by PHI was used, and the X-ray source was irradiated with monochrome AlK (200 μm, 35 W, 15 kV) to a measurement region of about 200 μm. Measurements were made. Furthermore, the thickness of the coating layer measured the thickness in a cutting edge ridgeline part. The results are shown in Table 3.

Next, a cutting test was performed using the obtained cutting tool under the following cutting conditions. The results are shown together in Table 3.
(Abrasion resistance test)
Work material: S45C (carbon steel)
Cutting speed: 250 m / min
Feed: 0.20mm / rev
Cutting depth: 1.5mm
Cutting condition: wet (use water-soluble cutting fluid)
Evaluation method: Time until the wear amount reaches 0.2 mm (minutes)
(Fracture resistance test)
Work material: S45C (carbon steel)
Cutting speed: 100 m / min
Feed: 0.25mm / rev
Cutting depth: 2.0mm
Cutting condition: Dry evaluation method: Number of impacts before breakage (times)

From Tables 1-3, sample No. 1 in which the temperature was lowered to 1150 ° C. in step (d) of the above steps in a gas atmosphere. In 8, without the surface region is formed, the ratio _{(b s} / _a s) is smaller than the ratio _{(B s} / _A s) even 2 less than 2, the wear resistance is lowered. In addition, in the above-described steps, the sample No. 1 in which the firing at the firing temperature C was performed at 1650 ° C. in vacuum. In No. 9, the ratio (b _s / a _s ) exceeded 10 and the ratio (B _s / A _s ) was larger than 10, and the wear resistance was lowered due to the decrease in the edge hardness. Furthermore, the sample No. in which the composition of the coating layer falls outside the scope of the present invention. In 10-17, both abrasion resistance and fracture resistance decreased. Furthermore, the sample No. 4 in which the thickness of the coating layer is thinner than 3.5 μm. In Sample No. 18, the abrasion resistance was poor and the thickness of the coating layer was more than 10 μm. In No. 19, wear progressed due to chipping of the coating layer.

  On the other hand, sample No. which is a cermet having a structure within the scope of the present invention. Nos. 1 to 7 exhibited excellent wear resistance and good fracture resistance. As a result, the tool life was long.

It is a scanning electron micrograph about the grinding | polishing surface in the cross section which shows an example of the surface coating member of this invention, and contains a cermet base | substrate and a coating layer. It is a scanning electron micrograph about (a) surface vicinity and (b) inside about the cermet base | substrate of the surface coating member of FIG. The other example of a cermet base | substrate is shown about the surface coating member of this invention, (a) Surface vicinity, (b) The scanning electron micrograph about the inside.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cutting tool 2 Hard phase 2a 1st hard phase 2b 2nd hard phase 3 Bonding phase 4 Cermet base | substrate 5 Covering layer 6 Inside 7 Surface area 8 Extreme surface area

Claims (5)

A cermet substrate in which a hard phase composed of a nitride or carbonitride of a periodic table 4, 5 and 6 metal containing Ti as a main component is bonded with a binder phase mainly containing Co or Ni, and a surface of the cermet substrate A surface coating member comprising a coating layer to be coated,
When the cross-sectional structure of the cermet substrate is observed, the hard phase is a composite carbonitride of a first hard phase mainly composed of TiCN, at least one of Group 4, 5, and 6 metals of the periodic table and Ti. Consisting of a second hard phase of solid solution,
In the surface region of the cermet substrate, wherein an average particle diameter of the first hard phase and a _s, when the average particle diameter of the second hard phase was b _s, a _s and b _s ratio of (b _s / a _s ) is 2 to 10, the average area occupied by the first hard phase with respect to the entire hard phase in the surface region is A _s, and the average area occupied by the second hard phase is B _s , A The ratio of _s to B _s (B _s / A _s ) is 2 to 10,
The coating layer has a thickness in a _{3.5~10μm, Ti 1-a-b} -c-d Al a W b Si c M d (C x N 1-x) ( however, M is Nb, At least one selected from Mo, Ta, Hf, and Y, 0.45 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.1, 0.01 ≦ c ≦ 0.05, 0 ≦ d ≦ 0. 1. A surface covering member comprising 0 ≦ x ≦ 1).   The second hard phase contains at least one of W and Nb, and has a large content of at least one of W and Nb in the central portion of the second hard phase, and W and Nb in the outer peripheral portion of the second hard phase. The surface covering member according to claim 1, wherein the content of at least one is small.   The surface covering member according to claim 2, wherein a ratio of (total mass of W and Nb) / (total mass of the entire metal element) in the outer peripheral portion of the second hard phase is 2 to 20%. The average particle size of the first hard phase in the interior of the cermet substrate and a _i, wherein when the average particle diameter of the second hard phase was b _i, a _i and b _i and the ratio of (b i _/ a _i ) is a 2-8, wherein b _s is greater than b _i, the average area of the first hard phase with respect to the entire hard phases in the interior of the cermet substrate is occupied by an a _i, occupied by the second hard phase The ratio (B _i / A _i ) between A _i and B _i when the average area is B _i is 1.5 to 5, and the B _s is larger than B _i. The surface covering member according to 2 or 3. Surface-coated member according to claim 4, wherein said b _s are present in a thickness range of 30~300μm from the b _i is greater than the surface area is the surface of the cermet substrate.