DD222349A1 - METHOD FOR PRODUCING A LAYER COMPOSITE ON A CARBIDE SUBSTRATE, IN PARTICULAR CUTTING INSERTS - Google Patents

Abstract

The aim of the invention is to increase the performance characteristics of silicon nitride coated cemented carbide substrates and to find an economical process for producing this layer of hard material. The object of the invention is to increase the adhesive strength of the silicon nitride layer. According to the invention, this is achieved by first depositing in known manner on the cemented carbide substrate an intermediate layer of compounds of the titanium-nitrogen-carbon system and subsequently depositing a layer consisting of metallic silicon in a thickness of 1 102 nm to 2 103 nm , This silicon layer completely enters the intermediate layer by diffusion annealing and the cover layer of silicon nitride with 1 103 nm to 1 104 thickness is deposited.

Description

Title of the invention

Process for producing a layer composite on a cemented carbide substrate, in particular cutting inserts

Field of application of the invention

The invention relates to a method for producing a layer composite on a cemented carbide substrate, in particular cutting inserts, by means of chemical vapor deposition, wherein the cover layer consists of silicon nitride.

Characteristic of the known technical solutions

It is known that performance and service life of highly stressed components and tools dur'oh the application of hard coatings Mitteis chemical vapor deposition (GYD) can be significantly increased _o - a wide Eaum assume the coatings of carbide cutting inserts for metal forming an _e In practice, The hard compounds described in DE-OS 21 42 601 of the system 'titanium-carbon-nitrogen enforced »reasons for this are the favorable properties

of the substrate layer composite, wherein alloy formations between. the layer-forming hard-material bonds and constituents of the carbide substrate play an important role. " -

Silicon nitride is also known as hard material * Silicon nitride is superior to titanium-carbon-nitrogen compounds as a cutting material due to its mechanical »thermal properties. GBPS 1.408.294 describes a silicon nitride layer« When coating tungsten carbide cutting inserts with silicon nitride, the different coefficients of expansion result of Carbide Substrate and Silicon Nitride Layer Under Thermal Stress to Crack and Peel the Layer "Numerous attempts have been made to balance the properties of the layer and substrate by the application of certain interlayers"

As apparent from DS-OS 20 18 662 ersichtlicfh, this requires additional complicated technological steps as well. Further layer-forming elements · Furthermore, in the AT-PS 33 6905 intermediate layers of rare metals are proposed _f allow the compensation of mechanical stresses between the layer and substrate due to their deformability »The rare metals, however, are usually not by chemical vapor deposition on the substrate, are expensive and significantly increase the technological effort *

Object of the invention. , ,

The aim of the invention is to increase the performance of a composite layer on cemented carbide substrates, in particular cutting inserts, wherein the cover layer consists of silicon nitride, and to find an economical method for producing the composite layer.

Explanation of the essence of the invention

The invention is based on the object, a method for producing a laminated composite with a cover ·. Layer of silicon nitride on Hartnietallsubstrate, in particular cutting inserts to find by chemical vapor deposition to increase the adhesion of the Siliziumnitriddeckschicht », Erf¬ this is achieved in that first in a known manner to the cemented carbide substrate, an intermediate layer of a compound of the system. Titanium-carbon-ticks is deposited and subsequently a layer consisting of

2 tallischem silicon is deposited in a thickness of 1-10 nm to 2-1CK nm, completely enters the intermediate layer once this silicon layer duröh diffusion annealing and the top layer of silicon nitride is deposited to _a US 1-1CKnm to 1-10 nm in thickness · The Deposition of the metallic silicon layer takes place at temperatures of 1173 to 1373 Kelvin from a hydrogen-containing gas mixture containing 0.01 to 0.2 percent by volume, preferably '0.05 to 0.1 percent by volume of gaseous Si Gl ^, during a period of 30 to 1200 Seconds, preferably 120 to 600 seconds · The diffusion annealing is carried out at a temperature of 1373 to 1473 Kelvin with a duration of 60 to 1800 seconds.

embodiment

The "invention is explained in more detail below with reference to an embodiment"

The hard metal body to be coated, for. B, 'an indexable insert, is located on a support in a vertically arranged quartz glass reactor and is heated by an externally arranged induction coil with high-frequency current, whereby the reactor is traversed by a mixture of hydrogen and argon.

After reaching a temperature of I323 Kelvin is the

-1 reactor a mixture of 5 x 63 "10 moles / min hydrogen 3" · 45 ^ O "^ mol / min of nitrogen and 8.5 ♦ 10" ⁴ mol / min

Titanium tetrachloride is fed in and a titanium nitride layer of about 8 × 1CK thick deposited on the cemented carbide body for 20 minutes. The supply of nitrogen and titanium tetrachloride is then terminated, the temperature is lowered to 1223 Kelvin and the hydrogen flow is reduced to a quantity of 3 × 10 × 10 -3. Silicon tetrachloride is admixed for a period of 150 s. A layer of silicon metal is deposited on the cemented carbide body. Thereafter, the temperature of the cemented carbide body is increased to 1423 Kelvin while maintaining the passage of hydrogen Then, the temperature is lowered to 1193 Kelvin, a flow rate of 6.1. 10 "" ² mol / min hydrogen, 6.1, 10 "" ² mol / min nitrogen, 3.03 i 1Ö "5 mol / min silicon tetrachloride and 6.1 · 10 mol / min ammonia and adjusted during

'..'. . ' ο

15 minutes, a ca 4 · _{β ΙΟ-} 'nm thick silicon nitride layer is deposited and thereafter the cemented carbide body in a hydrogen stream cooled ·

The metallographic examination of the cemented carbide body shows that there is no silicon metal as a self-standing phase between the titanium nitride layer and the silicon nitride layer. The microhardness of the titanium nitride layer has increased to 2400 to 2800 H compared to normally 2000-2200 HV. Increases the adhesion of the silicon nitride cover layer by heating the cemented carbide body under hydrogen to 1473 Kelvin and subsequent cooling, each with approximately 20 grd / s, shows no cracking or detachment of the silicon nitride covering layer.

Claims (3)

invention claim 1 "" Process for producing a Schichtrverbundes on cemented carbide substrates, in particular cutting inserts, by chemical vapor deposition, wherein the cover layer consists of silicon nitride, characterized in that. a) is deposited in a known manner on the cemented carbide substrate, an intermediate layer of a compound of the system titanium-nitrogen-carbon and below b) depositing a layer consisting of metallic silicon in a thickness of 1 × 10 nm to 2 × 10 -4 nm, c) this silicon layer completely enters the intermediate layer by diffusion annealing and d) the covering layer of silicon nitride with 1 · 1CK nm 4 is deposited to 1 x 10 nm thickness 2 · procedure according to point 1, characterized by that deposition of the metallic silicon layer at temperatures of 1173 to 1373 Kelvin from a hydrogen-containing gas mixture containing 0.01 to 0.02 percent by volume, preferably 0.05 to 0.1 percent by volume of gaseous Si .Gl ^, during a period of 30 to 1200 seconds, preferably 120 to 600 seconds. - 3 · procedure according to point 1,
characterized by the diffusion annealing is carried out at a temperature of 1373 to 1473 Kelvin with a duration of 60 to 1800 seconds.