MXPA99003512A - Cutting tool insert - Google Patents

Abstract

A cutting insert which comprises a rake face and a flank face wherein there is a cutting edge at the juncture of the rake face and the flank face. The cutting insert has a coating and a substrate wherein the coating is adherently bonded to the substrate. The substrate is a tungsten carbide-based cemented carbide wherein there is a zone of non-stratified cobalt enrichment beginning near and extending inwardly from a peripheral surface of the substrate. The bulk substrate has a porosity of greater than C00 and less than or equal to C02.

Description

CUTTING TOOL INSERT BACKGROUND The invention relates to a coated cemented carbide cutting insert having a substrate with a porosity (by Designation ASTM B 276-86, entitled 'Standard Test Method for Apparent Porosity in Cemented Carbides') of more than COO and less than or equal to C02, where there is a zone of binder enrichment, not stratified, that is, generally homogeneous, which starts near and extends away from the peripheral surface of the substrate .Therefore, there has been a coated cutting insert KC850 ® from Kennametal (KC850 is a registered trademark of Kennametal Inc., of Latrobe, Pennsylvania 15650, USA, for cutting inserts), which has a substrate with a porosity of C03 / C05, which has a binder enrichment zone On the surface, this binder enrichment is a type of stratified binder enrichment, which means that the binder enrichment is formed in different layers. binder metal ace. To the article by Nemeth et al., * Microstructural Characteristics and Cutting Performance of Kennametal High Resistance to Cutting Grade KC850", Proceedings of Tenth Plansee Seminar, Reutte, Tyrol, Austria, Metal erker Plansee AG (1981), pp. 613-627 , describes the coated cutting tool (or insert) 'KC850 from Kennametal. The coated cutting insert 'KC850® from Kennametal' has a three phase coating of TiC-TiCN-TiN, according to US Pat. No. 4,035,541, Smith et al., Entitled 'Cemented Carbide Body, Sintered, Coated with Three hats" .

Brief Description of the Invention The invention is a cutting insert, which comprises a sloped or beveled face and a side face, wherein there is a cutting edge at the junction of the inclined or beveled face and the side face. The cutting insert has a coating and a substrate, wherein the coating is adhesively bonded to the substrate. The substrate is a cemented carbide based on tungsten carbide, which has a bulk composition of between about 3 to about 12 percent by weight of cobalt, up to about 12 percent by weight of tantalum, up to about 6 percent by weight of niobium, up to about 10 by weight of titanium, and the rest of tungsten and carbon. There is a non-stratified cobalt enrichment zone that starts nearby and extends away from the peripheral surface of the substrate. The non-stratified enrichment zone has a porosity A. The bulky substrate has the highest porosity of COO and less than or equal to C02.

BRIEF DESCRIPTION OF THE DRAWINGS The following is a brief description of the drawings, which form part of this patent application: FIGURE 1 is an isometric view of a specific embodiment of a cutting insert of the SPGN 432 type; FIGURE 2 is a cross-sectional view of the cutting insert illustrated in FIGURE 1, taken along the line of cut 2-2; FIGURE 3 is an isometric view of a specific embodiment of a cutting insert of the SNG 433 type; and FIGURE 4 is a cross-sectional view of the cutting insert illustrated in FIGURE 3, taken along section line 4-4.

Detailed Description Referring to the figures in the drawings, the FIGURE 1 illustrates a specific embodiment of the present invention as an indexable cutting insert generally referred to as 10. The cutting insert 10 has cutting edges 12 at the inclined or beveled face junction 14 with the side faces 16. Although the cutting insert 10 shown in FIGURE 1, is of the SPGN 432 type with a ground or polished cutting edge, the applicant contemplates that the present invention includes other types or styles of cutting inserts with or without ground or polished cutting edges. FIGURE 2 shows a cross section of the cutting edge 12 of the cutting insert 10, taken along section 2-2 of FIGURE 1. The substrate generally designated 18 has an enriched zone without binder 20, i.e., an area comprising a central portion (or bulky region) of the substrate, and an area enriched with external (or peripheral) binder 22 near the edges of the periphery 24 and 26 of the substrate. The zone enriched with external binder 22 exhibits a binder enrichment of the non-stratified type. In other words, the zone enriched with binder 22 is generally homogeneous in nature. This is a distinction with respect to the stratified enrichment zone, in which the binder forms layers one on top of the other, as discussed in Kobori et al., Entitled 'Coated Enriched Layer Near the Surface of the Cemented Carbide' , Powder and Po der Metallurgy, Vol. 34, No. 3, pp. 129-133 (April 1987).

In a preferred embodiment, the substrate 18 is a cemented carbide substrate based on tungsten carbide containing at least 70 weight percent tungsten carbide, and most preferably at least 80 weight percent carbide of tungsten. The binder is preferably cobalt or a cobalt alloy and, preferably, has a bulk concentration of 3 to 12 weight percent. The preferred cobalt content by mass is between about 5 to about 8 weight percent. Even more preferably, the bulk cobalt content is between about 5.6 to about 7.5 weight percent. The substrate 18 also contains carbide and / or carbonitride-forming elements in solid solution, such as titanium, hafnium, zirconium, niobium, tantalum and vanadium, with those elements being preferably selected from titanium, niobium and tantalum, either alone or in combination with each other or with tungsten. These elements can be preferably added to the sample as a carbide, nitride or carbonitride, and more preferably, as a nitride, and more preferably as tantalum carbide. (niobium) and titanium nitride. Preferably, the concentration of these elements is within the following ranges: up to 12 weight percent of tantalum, up to 10 weight percent of titanium, and up to 4 weight percent of niobium. More preferably, the sum of the tantalum content and the niobium content is between about 3 and about 7 weight percent, and the titanium content is between about 0.5 and about 5 weight percent. More preferably, the sum of the tantalum content and the niobium content is between about 5.0 and about 5.9 weight percent, and the titanium content is between about 1.7 and about 2.3 weight percent. In the voluminous region 20 of the substrate 18, these elements (ie, titanium, hafnium, zirconium, niobium, tantalum and vanadium) form, at least to some degree and preferably, for the most part, carbides in solid solution and / or carbonitrides in solid solution with tungsten carbide in the substrate. In the enriched zone 22, the carbides and / or carbonitrides in solid solution have been completely or partially depleted, so that the tungsten carbide and cobalt comprises the majority of the composition of the zone enriched with binder 22. Within the enriched zone with binder 22, the binder content (e.g., cobalt) should reach a maximum value that is between about 125 to about 300 percent. A more preferable range of binder enrichment is between about 150 and about 300 percent of the total binder content. The most preferable range of binder enrichment is between about 200 and about 300 weight percent of the total cobalt concentration in the substrate. The zone enriched with binder 22 preferably extends to the peripheral surfaces of the substrate 24 and 26. Alternatively, a thin layer adjacent to those peripheral limits (24, 26) may exist in which the cobalt content has been reduced. due to evaporation during sintering of the substrate, so that the binder enrichment zone (e.g., cobalt) 22 extends to near the peripheral surface (24, 26) of the substrate 18. The thickness of the zone enriched with binder is preferably up to about 50 micrometers (μm). Attached to the peripheral boundaries 24 and 26 of the substrate 18 is a hard coating, designated by the brackets as 29, which preferably has one or more layers applied by chemical vapor deposition (CVD) or a combination of CVD and physical deposition techniques. By steam (PVD). MTCVD techniques (medium temperature CVD) can be used to apply a layer, such as a layer of titanium carbonitride. Those layers may comprise a base layer 30, an intermediate layer 32, and an outer layer 34.

Although FIGURE 2 illustrates the layers as having different thicknesses, it should be appreciated that this is for illustrative purposes only. The thickness of each layer (30-, 32, 34) depends on the specific application of the cutting insert. The base layer 30 is deposited directly on the surface (24, 26) of the substrate 18. The thickness of the base layer 30 preferably varies between about 3 microns (μm) and approximately 6 μm. Although the composition of the base layer may vary, preferred compositions may include, for example, titanium carbide, titanium carbonitride and titanium nitride. The intermediate layer 32 is deposited directly on the surface of the base layer 30. The thickness of the intermediate layer 32 varies between approximately 2 μm and approximately 5 μm. Although the composition of the intermediate layers may vary, preferred compositions may include titanium carbonitride, titanium nitride, titanium carbide, alumina, titanium aluminum nitride, and combinations thereof. The outer layer 34 is deposited directly on the surface of the intermediate layer 32. The thickness of the outer layer 34 varies between about 1.5 μm and about 4 μm. Although the composition of the outer layer may vary, preferred compositions may include titanium nitride, titanium carbonitride, titanium nitride and aluminum and alumina.

Although the above description mentions suitable candidates for the coating layers, the preferred coating scheme uses a titanium carbide base coat, an intermediate coating of titanium carbonitride, and an outer coating of titanium nitride. U.S. Patent No. 4,035,541, to Sith et al. , discloses a three-layer coating that is applicable to the cutting insert illustrated in FIGURE 2. In addition, the coating scheme can be applied by a combination of CVD and PVD, such as those processes described in U.S. Patent No. 5,250,367, of Santhana et al. , for a * Cutting Insert Coated by CVD and PVD Rich in Binder ", and US Pat. No. 5,266,388, by Santhanam et al., for a" Coated Cutting Insert Rich in Binder ". The applicant therefore incorporates U.S. Patent No. 4,035,541, Smith et al., U.S. Patent No. 5,250,367, Santhanam et al., And U.S. Patent No. 5,266,388, Santhanam et al., Here by reference. . As shown in FIGURE 2, for a cutting insert used in grinding applications, it is preferred that the binder-rich zone 22 be present below the peripheral limits that are parallel to the sloped or beveled face 14 and the side faces 16 of the cutting insert 10. In other applications such as, for example, turning, it was contemplated that the enriched zone would be present only on the inclined or beveled face with the enrichment zone having been removed (for example, by grinding or polishing) the other faces In this regard, the cutting insert 40 described in FIGURES 3 and 4, which is a cutting insert of the SNG 433 type, has a microstructure in which the enriched zone is present only under the inclined or bevelled faces. Referring to FIGURES 3 and 4, the cutting insert 40 has four side faces 42, which intersect with a sloped or beveled face 44 and another sloped or beveled face (not shown) opposite the sloped or bevelled face 44 to form eight cutting edges 48. The cutting insert 40 has a substrate generally designated as 49 with the peripheral boundary 52 on the sloped or beveled face and a peripheral boundary 54 on the side face. The substrate 49 has a bulky portion 50, which comprises the majority of the substrate 49, and a binder enrichment layer 56 near the peripheral boundary 52 on the sloped or bevelled face. The enrichment of the binder is absent from the voluminous portion 49 that includes the volume near the peripheral boundary 54. The substrate 49 for the cutting insert 40 is essentially of the same composition as the cutting insert 10. The levels of binder enrichment are also essentially the same for the cutting insert 40 than those for the cutting insert 10. The basic coating scheme (shown in brackets as 59) is also essentially the same for the cutting insert 40 as for the cutting insert 10. In this respect, the cutting insert 40 has a base coat layer 60, an intermediate cover layer 62, and an outer cover layer 64. The present invention is further described by the following example, which is provided solely for the purpose of description, and is not intended to limit the scope of the invention. Example No. 1 of the invention is set forth in conjunction with Comparative Examples Nos. 1 to 3. For examples of the invention and comparatives, the powders of the substrate contained approximately 5.8 weight percent cobalt, approximately 5.2 weight percent tantalum weight, approximately 2.0 percent by weight of titanium, and the rest was tungsten and carbon. The titanium was added in the form of titanium nitride. The tantalum was added in the form of tantalum carbide. Tungsten was added as tungsten carbide and tungsten and carbon was added in the form of tungsten metal and carbon black. The mixtures were loaded at various carbon levels as set forth in Table I below.

Table I Carbon Levels Loaded in the Examples The 5 kilograms (kg) of the mixture charge for each example was added to a steel milling jug of 19 centimeters (7.5 inches) in internal diameter by 22.9 centimeters (9 inches) along with 21 kg of cemented carbide cycloids 1 centimeter (3/8 inch) in diameter and heptane to the top of the jar. The mixture was stirred for 40 hours at 52 revolutions per minute (rpm) at room temperature. The suspension of each charge was dried, paraffin was added as a fugitive binder, and the powders were granulated to provide the proper flow properties. The granulated powders were compressed into cutting insert pieces of the SNG433 type and sintered at 2650 ° F (1456 ° C) for about 30 minutes under a vacuum. Those shear insert substrates were then allowed to cool in the furnace.

The sloped or beveled faces were then ground and the pieces of cutting inserts were reheated to 2650 ° F (1456 ° C) for approximately 60 minutes under a vacuum, followed by a controlled cooling of 100 ° F (56 ° C) / hour until reach 2100 ° F (1149 ° C). Table II below shows the properties of the resulting substrates after reheating.

Table II Compositions and Physical Properties of the Comparative Examples and Examples of the Present Invention Table II Compositions and Physical Properties of the Comparative Examples and Examples of the Present Invention (continued) The pieces of cutting inserts were rectified and polished peripherally, so that in the resulting substrate had cobalt enrichment on the inclined or beveled faces and the side faces had no cobalt enrichment, the pieces of cutting inserts were then coated with a coating of three phases according to U.S. Patent No. 4,035,541. The base layer was titanium carbide applied via CVD at a thickness of 4.5 micrometers (μm). The intermediate layer was made of titanium carbide applied via CVD at a thickness of 3.5 μm.

The top layer was titanium nitride applied via CVD at a thickness of 3.0 μm. The operation of the turning for the comparative examples and the example of the invention, was done according to the following test procedure: Workpiece Material: AISI 4340 steel (300 BHN) Turning conditions: 450 surface feet per minute (sfm) ) [137.2 surface meters per minute] or 550 sfm [167.8 surface meters per minute], feeding .020 inches per revolution (ipr) [.508 centimeters per revolution} and .1 inches (.254 centimeters) of depth of cut (doc). Coolant: Regular TrimSol (20%) Inserts Type SNG-433 with radio rectification (.003 inches) [, 0076 centimeters], edge preparation. Insect Life Criteria: Maximum Lateral Wear = .030 inches (.076 centimeters) Uniform Lateral Wear = .015 inches (.038 centimeters) Breakdown = .030 inches (.076 centimeters) Crater Wear (depth) = .004 inches (.010 centimeters) Tip Wear = .030 inches (.076 centimeters) Grooving Depth = .030 inches (.076 centimeters) The turning operation of the comparative examples and the example of the invention will also be effected according to the following procedure: Workpiece Material: AISI 1045 steel (210 BHN) Turning conditions: 750 sfm (228.8 surface meters per minute) .020 ipr [.508 centimeters per revolution] .1 inches (.254 centimeters) depth cutting (doc). Coolant: Regular TrimSol (20%) Inserts Type SNG-433 with radio rectification (.003 inches) [.0076 centimeters], edge preparation. Insert Life Criteria: Maximum Lateral Wear = .030 inches (.076 centimeters) Uniform Late Wear = .015 inches (.038 centimeters) Breakdown = .030 inches (.076 centimeters) Crater Wear (depth) = .004 inches (.010 centimeters) Tip Wear = .030 inches (.076 centimeters) Grooving Depth = .030 inches (.076 centimeters) The impact resistance of the comparative examples and the Example of the invention was determined according to the following grooved bar turning test procedure (41L50 steel): Speed: 350 sfm (106.8 surface meters per minute) Cutting depth = .1 inches (.254 centimeters) Feeding = at the start the feeding was of .015 inches per revolution (.038 centimeters per revolution) with feed increasing to .005 inches per revolution (.0127 centimeters per revolution) every 100 impacts, until the test reached 800 impacts, when the feed was .050 inches per revolution (.127 centimeters per revolution) or until the break, whichever comes first. Table III below sets forth the test results for the test of Comparative Examples Nos. 1 to 4 and Example No. 1 of the invention.

Table III Life of the Insert and Results of the Resistance Test Sharpened for Comparative Examples No. 1 to 3 and Example No. 1 of the Invention The nominal porosity of Table III was determined according to ASTM Designation B 276-86, entitled 'Standard Test Methods for Apparent Porosity in Cemented Carbides.' The depth of binder enrichment was determined by optical examination of a section. cross section of the specimen, via metallography to a magnification of 1500X.The sharpening resistance exposes the number of impacts until the break or the test ended at 800 impacts, via the grooved bar test described above.The results of the turning test reflect the tool life of the inserts in minutes from the test procedures described above The data in Table III show very clearly that Example No. 1 of the invention has excellent grinding resistance of the slotted bar ( 800 impacts.) Excellent tool life was also demonstrated in the turning of the 1045 and 4340 steels. Total metallocarbant ages of Example No. 1 of the Invention are superior to those of all the other examples shown (ie, Comparative Examples Nos. 1 to 3 and the coated cutting insert 'KC850® of Kennametal'). More specifically, the sharpening resistance of Example No. 1 of the invention is equivalent to the sharpening resistance of Comparative Examples Nos. 2 and 3 higher in carbon, and superior to the sharpening resistance of Comparative Example No. 1 , lower in carbon. Example No. 1 of the invention also has a sharpening resistance which is equivalent to that of Kennametal's "KC850® Coated Cutting Insert" of upper carbon alloy, together with the excellent sharpening strength of Example No. 1 of the Invention also demonstrated a life of the upper 1045 steel tool, as compared to the other examples with high carbon content Example No. 1 of the invention had a tool life of 13.1 minutes compared to 10.7 minutes for the Comparative Example No. 2, 5.6 minutes for Comparative Example No. 3, and 5.3 minutes for the coated cutting insert 'KC850® from Kennametal. "The life of the steel tool 4340 of Example No. 1 of the invention is also greater than the life of the tool of the other examples with a higher carbon content with sharpening resistance (800 impacts). (for example, Comparative Examples Nos. 2 and 3, and the coated cutting insert 'KC850® from Kennametal'). Although the life of the steel tool 4340 and 1045 was only equivalent to, or slightly less than, that of Comparative Example No. 1 with lower carbon content, Example No. 1 of the Invention has a higher grinding resistance than the which is sustained at 800 impacts versus 635 impacts for Comparative Example No. 1.

It is very evident that the present invention presents a cutting insert with improved characteristics over Comparative Examples Nos. 1 to 3, as well as the coated cutting insert 'KC850® from Kennametal. "The improved characteristics are especially evident in conjunction with the impact resistance and the wear resistance demonstrated in the interrupted and continuous turning of the steel, as shown above.All patents and other documents identified in this application are hereby incorporated by reference.Other embodiments of the invention will be apparent to Those skilled in the art from the consideration of the specification or practice of the invention described herein: It is intended that the specification and examples be considered as illustrative only, with the true scope and spirit of the invention being indicated by the following claims .

Claims (12)

CHAPTER CLAIMEDICATORÍO Having described the invention, it is considered as a novelty and, therefore, the content is claimed in the following:

1. A cutting insert, characterized in that it comprises: a sloped or beveled face and a side face, a cutting edge at the junction of the inclined or beveled face and the side face; the cutting insert has a coating and a substrate, wherein the coating is adhesively bonded to the substrate; the substrate is a cemented carbide based on tungsten carbide having a bulk composition of from about 3 to about 12 weight percent cobalt, up to about 12 weight percent tantalum, up to about 6 weight percent niobium, up to about 10 weight percent titanium, and the rest comprised of tungsten, nitrogen and carbon; wherein the cobalt concentration is enriched in a non-stratified cobalt enrichment zone that begins near and extends away from a peripheral surface of the substrate, the enriched zone has a maximum cobalt concentration of between about 125 and 300 percent of the cobalt in the bulky substrate; and where the bulky substrate has a greater porosity of COO and less or equal to C02.

The cutting insert according to claim 1, characterized in that the substrate has a bulk composition comprising between about 5.6 and about 7.5 weight percent cobalt, between about 5.0 and about 5.5 weight percent tantalum, between about 1.7 and about 2.3 weight percent titanium, up to about 0.4 weight percent niobium, and the rest comprised of tungsten and carbon and nitrogen.

3. The cutting insert according to claim 1, characterized in that the enriched zone has a maximum cobalt content between about 150 and about 300 percent of the cobalt in the bulky substrate.

The cutting insert according to claim 1, characterized in that the enriched zone has a maximum cobalt content between about 200 and between about 300 percent cobalt in the bulky substrate.

The cutting insert according to claim 1, characterized in that the non-stratified cobalt enrichment zone extends to a depth of between about 40 micrometers and about 50 micrometers of the peripheral surface.

6. The cutting insert according to claim 1, characterized in that the substrate has a bulk composition of about 5.8 weight percent cobalt, about 5.2 weight percent tantalum, about 2.0 weight percent titanium, and the rest comprised of tungsten and carbon.

The cutting insert according to claim 1, characterized in that the substrate is formed from a consolidated mass of starting powders.

8. The cutting insert according to claim 7, characterized in that the starting powders include titanium nitride. The cutting insert according to claim 7, characterized in that the starting powders include tantalum carbide. The cutting insert according to claim 7, characterized in that the starting powders include niobium carbide. The cutting insert according to claim 7, characterized in that the starting powders include tungsten carbide. The cutting insert according to claim 7, characterized in that the starting powders include carbon.