SE527693C2 - Tray for coating cutting tool inserts using chemical vapor deposition or moderate temperature chemical vapor deposition, has insert contacting face with coating comprising oxide inner layer and wear resistant outer layer - Google Patents

Abstract

The tray face on which the inserts are positioned has a coating comprising a spray coated oxide inner layer and a wear resistant outer layer of a carbide, nitride and/or oxide of a Group 4b, 5b or 6b metal or aluminium. A graphite or ceramic tray for coating cutting tool inserts with a wear resistant coating using a CVD (Chemical Vapour Deposition) and/or MTCVD (Moderate Temperature Chemical Vapour Deposition) method in which the inserts are positioned on the tray has a face intended for contact with the inserts which has a coating comprising a spray coated oxide inner layer and a wear resistant outer layer of a carbide and/or nitride and/or oxide of at least one metal chosen from Group 4b, 5b, 6b and aluminium.

Description

U 20 25 30 35 527 693 2 shape, with or without a central hole etc ... Therefore, a batch charging system which necessarily needs different arrangements for different types of inserts in order to have a uniform charge density, will never function further rationally in a production environment, set at a low cost and short lead time.

EP 454 686 describes a charging system, especially intended for PACVD, where the inserts are stacked on top of each other on a central pin with or without a spacer ring in between.

US 5,576,058, US 5,759,621 and SE 9400950-3 describe a batch charging system based on various arrangements of pins comprising a foot, a shoulder, a neck and a head.

A commonly used charging arrangement is to place the inserts in holes or grooves in a washer. This method will give contact marks on the cutting edge or on the release sides of the inserts. When using this arrangement, very careful handling, transport and loading of the washers is required to prevent the inserts from falling out of position.

In another method, the inserts are threaded onto a bar. The rods can be arranged vertically as in EP 454,686 with the same inconveniences as discussed above or horizontally. The main disadvantages of the horizontal arrangement are the lack of university for different insert geometries. In addition, the washer can only be used for inserts with holes.

The most universal measures are based on simply placing the inserts on a surface, separated by the necessary spaces between them, either on a woven metal mesh or on some other solid surface (often made of graphite). The load is built up by stacking the metal nets and / or graphite trays on top of each other. The major disadvantage of this method has so far been the contact marks between nets or washers and inserts that are always formed. Often, some finishing may be needed to remove protruding marks. Another disadvantage with the use of woven washers is that the inserts can slide together relatively easily before coating, resulting in uncoated surfaces on the insert.

It is an object of the present invention to provide a CVD and / or MTCVD batch charging system which allows a rational production method without a large number of different arrangements depending on different types of inserts, i.e. a universal, inset geometry-independent system. It is a further object of this invention to provide a CVD and / or MTCVD batch charging system which avoids the problems of prior art batch charging system contact marks and / or that the inserts slide together before or under occupancy.

DEFINITIONS In the following description we will use terms defined as follows: Spraying defines a coating preferably precipitated by a spraying process such as thermal spraying, plasma spraying etc ...

Pre-coating defines a CVD and / or MTCVD coating coated on the tray or backing material prior to initial use in the coating with durable CVD and / or MTCVD coatings on top of final products, defined herein as a production coating.

The critical size of the protruding marks, where they begin to affect the properties of the tool, is defined to a maximum height of 20 μm.

BRIEF DESCRIPTION OF THE FIGURES Fig. 1 is a SEM (Scanning Electron Microscope) image in 50X magnification of a graphite wafer which has been pre-coated and then production coated with a coating of a total thickness of about 100 μm CVD and MTCVD coating of type Ti (C, N) + Al2O3 + TiN.

Fig. 2 is an SEM (Scanning Electron Microscope) image in SOX magnification of a graphite wafer which before first use has been spray coated with an approximately 50 μm ZrO 2 + Y 2 O 3 layer and then precoated, then production coated with a total thickness of about 100 μm CVD and MTCVD Ti (C, N) + Al 2 O 3 + TiN type coating according to the present invention.

Fig. 3 is a LOM (Light Microscope) image in 100X magnification of a cross section of a graphite wafer (a) which before first use has been spray coated with an approximately 50 μm ZrO2 + Y2O3 layer (b) and then provided with a precoat (c ) and a production coating (d). Pre-coating and production coating, in this case consisting of CVD and MTCVD coatings of Ti (C, N) + Al 2 O 3 + TiN material, are a total of about 50 μm thick.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, it has surprisingly been found that if the surface of a tray is provided with a certain spray coating, it is possible to avoid large contact marks and especially protruding marks. This optimal surface treatment comprising a spray coating substantially eliminates the problem in the prior art.

The tray can be made of graphite, metals, composites, ceramics or combinations thereof. Other materials from which a washer can be produced could also be used provided that they have a sufficient strength at 1000 ° C. Preferably, the tiles are made of graphite. The washers may have holes and / or a macro surface structure such as pyramids formed in the material to allow a uniform gas flow and thereby guarantee a uniform coating thickness. However, uniform coating thickness need not be a priority if the inserts are single-sided and therefore a surface structure may not be necessary.

In a preferred embodiment, a surface with desired properties is obtained by depositing a coating thereon using a spray coating technique such as plasma spraying, thermal spraying and other similar techniques. The spray coating process can be of either the hot or cold type.

The spray coating can be deposited on both sides of the washer, but it is necessary only on the side that is to be in contact with the inserts.

The spray coating comprises metal oxides, preferably ZrO2 and / or YZO3. Preferably the content of ZrO2 is more than 50% and most preferably more than 75%. Best properties are obtained when a mixture of ZrO2 and Y2O3 is used.

The total average coating thickness of said spray coating on the side in contact with the inserts is between 5 and 300 μm, preferably between 25 and 200 μm. Fig. 3 illustrates the difficulties in discussing and / or specifying the exact coating thickness of the spray coating due to the unevenness, so that only a rough average can be given.

Before precipitating the spray coating, it is important that the washer is properly cleaned by blasting, preferably dry, followed by brushing and / or cleaning with compressed air. This will offer the advantage of improved adhesion to the coatings.

The spray-coated layers can be deposited directly on the tray as a single layer or as a multilayer consisting of different metal oxides. Interlayers of other materials may be advantageous to improve the bond between the graphite and the sprayed oxide layer and / or between different sprayed oxide layers. A first intermediate CVD and / or MTCVD coating based on TiC and / or Ti (C, N) and / or Al2O3 layers can also be deposited on the tray before any spray coating is deposited.

Table 1 shows the influence on the surface roughness from the use of the spray coating.

Table 1 Tray variant Ra, arithmetic mean, pm a, Graphite washer + 10 um 3.9 pre-coating b, Graphite washer, with ZrO2 + Y2O3 + 10 pm Pre-coating spray-coated 11 Before use for production coating, the spray-coated tray is preferably pre-coated with a CVD and / or MTCV coating based on TiC and / or Ti (C, N) and / or Al 2 O 3 and / or TiN, as single or multilayer with a total coating thickness between 2 and 150 μm, preferably between 5 and 50 μm.

Post-heat treatment or intermediate heat treatment in an inert or reactive atmosphere of the spray-coated tray can also be used to increase performance by improving the adhesion of the coating.

The present invention has been described with reference to inserts, but it is obvious that it can also be used to advantage for treating other types of coated components, eg drills, end mills, wear parts, etc ..

Example 1 - A graphite wafer was precoated with an MTCVD coating of Ti (C, N) + Al 2 O 3 + TiN of a total thickness of 10 μm. The washer had an uncoated surface roughness Ra of 3.9 μm, see table 1 variant a, here referred to as variant A. Fig. 1 is an SEM (Scanning Electron Microscope) image in 5OX magnification of the coating in top view.

The same type of washer used for variant A was coated with an approximately 50 μm thick spray coating of ZrO2 + Y2O3 on the washer before first use. The wafer was then pre-beaded with a MTCVD coating of Ti (C, N) + Al 2 O 3 + TiN of a total thickness of 10 μm. The spray-coated surface finish, Ra, was 11 μm, see Table 1 in variant b, here referred to as variant B. Fig. 2 is an SEM (Scanning Electron Microscope) image in 50X magnification of the coating in top view.

Carbide inserts of the form SNUN120408 with a composition of 91 wt% WC - 9 wt% Co were used. Prior to coating, the uncoated substrates were cleaned. An MTCVD production coating of Ti (C, N) + TiC + Al 2 O 3 + TiN with a total coating thickness of about 10 μm was precipitated on the inserts. A total of four washers per variant were used and sixteen inserts were placed on top of each of the washers. Fig. 3 is a LOM (Light Microscope) image in 200X magnification of a cross section of a used graphite tray wherein (a) is graphite, (b) is the spray coated ZrO2 + Y2O3 layer, (c) is the precoat and (d) the production coating . After production coating, the inserts were examined for contact marks. If the marks were of the protruding type, the maximum height of the protrusion was measured with a Nikon optical device. If more than one protruding mark on an insert was found, the maximum height was taken as a measure of the current insert. Depending on the height of the protruding mark, the inserts were classified into four different classes: Class 1: No marks Class 2: Marks <10 um Class 3: 10 um <Marks <20 um Class 4: Marks> 20 um, Not approved The measured inserts were coated in a first production coating cycle after pre-coating the washers. Table 2 below summarizes the results.

Table 2 Variant A Variant B Minimum (um) 0 0 Maximum (um) 25 12 Class 1 (%) 21.3 53.3 Class 2 (%) 17.6 35.2 Class 3 (%) 56.8 11.5 Class 4 (%) 4.3 0 Not approved NOW 20 It can be clearly seen that variant B received much fewer and smaller marks than variant A. Using the present invention, all inserts are approved, ie protruding marks less than 20 μm, while using prior art 4% are not approved. .

Example 2 The same trays as in Example 1 were tested using the same analysis and classification method but after also nine production coating cycles (production coated a total of ten times).

Variant D corresponds to variant A (in example 1) but use longer time.

In the same way, variant E corresponds to variant B. The measured and classified inserts were coated in a production coating cycle number nine after pre-coating. All production coating cycles were of the same type as in Example 1. The thickness of the total production coating was about 100 μm. Table 3 below summarizes the results.

Table 3 Variant D Variant E Minimum (um) 12 0 Maximum (um) 112 40 Class 1 (%) O 64.1 Class 2 (%) 22.8 20.3 Class 3 (%) 32.2 10.9 Class 4 (%) 45.0 4.7 Variant E, as is according to the present invention, continues to show smaller and fewer marks. Using the present invention, 95.3% of the inserts were approved, while using known technology, 55.0% were approved.

Claims (8)

20 30 527 693 8 Requirements 1. l. Washer for coating inserts for prestressing machining with a durable coating using CVD and / or MTCVD methods, the inserts being placed on the washer made of graphite or ceramic, characterized in that the coating is at least on that side which is in contact with the inserts comprises an inner spray-coated oxide layer based on metal oxides from groups 3b, 4b, 5b, 6b and Al with an average thickness of between 5 and 300 μm, preferably between 25 and 200 μm, followed by a durable coating based on on Tic and / or Ti (C, N) and / or Al 2 O 3 and / or TiN, single or multilayer, with a total coating thickness between 2 and 150 μm, preferably between 5 and 50 μm. Tray according to Claim 1, characterized in that the spray coating material is based on ZrO 2. Tray according to claim 2, characterized in that the ZrO 2 content in the spray coating material is more than 50%, preferably more than 75%. Tray according to one of the preceding claims, characterized in that the spray coating material contains Y 2 O 3. Tray according to one of the preceding claims, characterized in that the surface roughness of the spray-coated tray, Ra, is greater than 5 μm. Tray according to any one of the preceding claims, characterized in that the tray material is graphite. 7. A method of coating inserts for prestressing machining with a durable coating using CVD and / or MTCVD methods, the inserts being placed on a tray made of graphite or ceramic characterized by the use of a tray according to any one of the Claims 1-6. Use of a washer according to any one of claims 1-6 for coating inserts for prestressing machining with a durable coating using CVD and / or MTCVD methods, the inserts being placed on the washer.