Title of Invention	A METHOD OF SINTER COATING FOR THR FORMATION OF WEAR RESISTANT LAYERS ON HARD METALS
Abstract	ABSTRACT: Disclosed herein is a method of sinter coating for the formation of wear resistant layers on hard metal comprising the steps of sintering of the hard metal at varying pressures from 0.02 mbar to 100 mbar different active gases like methane, hydrogen, carbon monoxide, argon and nitrogen in combination with vacuum (0.003 mbar to 0.5 mbar) at different temperature ranges from 500 degrees C to 1600 degree C to obtain the ceramic layers of thickness from 1 micron upwards on top of the hard metal, maintaining the flow rate of these gases from 1 1t/min to 60 1ts/min and the hard metal in addition to tungsten carbide and the binder phase contains alloying carbides and nitrides not less than 1%.

Title of Invention

A METHOD OF SINTER COATING FOR THR FORMATION OF WEAR RESISTANT LAYERS ON HARD METALS

Abstract

ABSTRACT: Disclosed herein is a method of sinter coating for the formation of wear resistant layers on hard metal comprising the steps of sintering of the hard metal at varying pressures from 0.02 mbar to 100 mbar different active gases like methane, hydrogen, carbon monoxide, argon and nitrogen in combination with vacuum (0.003 mbar to 0.5 mbar) at different temperature ranges from 500 degrees C to 1600 degree C to obtain the ceramic layers of thickness from 1 micron upwards on top of the hard metal, maintaining the flow rate of these gases from 1 1t/min to 60 1ts/min and the hard metal in addition to tungsten carbide and the binder phase contains alloying carbides and nitrides not less than 1%.

Full Text	The invention is about the process of sinter coating for the formation of wear resistant layers on hard metals in the sintering process. PRESENT STATE OF THE ART: The wear resistant surface layers are composed of ceramic carbides / carbo-nitrides / borides and can be formed either as individual layers of carbides or nitrides etc or as a combination of all. The binder content in the ceramic layers varies from 0% to 30% mass. The hard metal substrates contain 95% to 75% wear resistant material with the binder made of cobalt/nickel/molybdenum/aluminium varying from 5% to 25% mass. As per know technology ceramic layer coatings of high wear-resistance are obtained on hard metals primarily in two stages: Sintering of hard metals in which green compacts are subjected to heat treatment (sintering) either under vacuum or a reducing/inert atmosphere to obtain the sintered hard metal. Subsequently, coating processes like CVD, PVD, PACVD, MTCVD, etc are employed wherein the sintered hard metal is subjected to deposition of different ceramic compounds on the surface of the hard metal either through a chemical process or ionic process. LIMITATIONS: In the above mentioned methods: Cost is high due to a separate post-sintering coating operation. No metallurgical bond between the ceramic coating and the hard metal substrate leading to limitations in coating adhesion. - The coatings are always pure ceramic layers with no options for the formation of multiphase ceramic layers with a binder, resulting in brittle coatings. OBJECT OF THE PRESENT INVENTION: The aim of the present invention is to get a ceramic coating on hard metal at low cost, with a better bond between the coating and the substrate and to reduce the brittleness of the coated layers by producing the coating in the sintering process. It is a functionally gradient material wherein the surface layers are more wear resistant than the remaining portion of the hardmetal tool. Functionally in a metal cutting application, the surface of the tool needs to be more wear resistant to improve the cutting process. In the conventional Hardmetal cutting tool, selective hardening of the surface is not possible. In the conventional tool, a stand-alone process called the CVD or Chemical Vapour Deposition technique is adapted to deposit ceramic coatings on hard metal tools to improve the surface hardness or wear resistance. But in the new process the entire selective hardening is carried out in the process of consolidation or sintering, chemicals are not used unlike CVD and so the process for the present invention is Bio-friendly. More economical as CVD is a costly process. Since the basic hard metal itself is tailored to get the surface layers of high wear resistance, the bond between the layers and the tool is strong. In CVD, the layers deposited are external and the bonding strength with parent hard metal has its limitation. DETAILED DESCRIPTION: During the normal sintering cycle at varying pressures from 0.02 mbar to 100 mbar different active gases like methane, hydrogen, carbon monoxide, argon and nifrogen are used in combination with vacuum (0.003 mbar to 0.5 mbar) at different temperature ranges from 500 degrees C to 1600 degree C to obtain the ceramic layers of thickness from 1 micron upwards on top of the hard metal. The flow rate of these OBJECT OF THE PRESENT INVENTION: The aim of the present invention is to get a ceramic coating on hard metal at low cost, with a better bond between the coating and the substrate and to reduce the brittleness of the coated layers by producing the coating in the sintering process. It is a functionally gradient material wherein the surface layers are more wear resistant than the remaining portion of the hardmetal tool. Functionally in a metal cutting application, the surface of the tool needs to be more wear resistant to improve the cutting process. In the conventional Hardmetal cutting tool, selective hardening of the surface is not possible. In the conventional tool, a stand-alone process called the CVD or Chemical Vapour Deposition technique is adapted to deposit ceramic coatings on hard metal tools to improve the surface hardness or wear resistance. But in the new process the entire selective hardening is carried out in the process of consolidation or sintering, chemicals are not used unlike CVD and so the process for the present invention is Bio-friendly. More economical as CVD is a costly process. Since the basic hard metal itself is tailored to get the surface layers of high wear resistance, the bond between the layers and the tool is strong. In CVD, the layers deposited are external and the bonding strength with parent hard metal has its limitation. DETAILED DESCRIPTION: During the normal sintering cycle at varying pressures from 0.02 mbar to 100 mbar different active gases like methane, hydrogen, carbon monoxide, argon and nitrogen are used in combination with vacuum (0.003 mbar to 0.5 mbar) at different temperature ranges from 500 degrees C to 1600 degree C to obtain the ceramic layers of thickness from 1 micron upwards on top of the hard metal. The flow rate of these gases vary from 1 It/min to 60 Its/min. The hard metal in addition to tungsten carbide and the binder phase contains alloying carbides and nitrides not less than 1%. Hard metals contain a uniform mixture of varying levels of tungsten carbide (WC), hard & wear resistant ceramic carbides and nitrides of the elements of Group: IV B and V B of the periodic table like titanium, tantalum, zirconium and others along with the soft elements of the GroupVIII like cobalt, nickel and others. In the powder metallurgy of hard metals, the powder mixtures containing all these compounds & elements are compacted known as the green compacts. Green compacts are soft and contain high level of porosity, which is removed in the subsequent process called sintering. Sintering consolidates the green compacts removing all the pores and makes the hard metals hard. It also results in uniform distribution of all the phases containing the carbides and nitrides and the soft metals. This results in isotropic characteristics. In the new process, the carbides and nitrides of the elements of Group: IV B and V B are made to migrate to the surface of the hard metals during sintering, to form layers of these compounds. These compounds impart high wear resistant property to the surface of hard metals. This migration is effected using special gases like methane, hydrogen, argon and necessarily nitrogen. The quantum of migration depends on the process conditions like the partial pressures of these gases, temperature ranges and the basic composition of the hard metals and the quantum of migration affects the extent wear resistance obtained at the surface. WE CLAIM: 1. A method of sinter coating for the formation of wear resistant layers on hard metal comprising the step of: i) sintering of the hard metal at varying pressures from 0.02 mbar to 100 mbar different active gases like methane, hydrogen, carbon monoxide, argon and nitrogen in combination with vacuum (0.003 mbar to 0.5 mbar) at different temperature ranges from 500 degrees C to 1600 degree C to obtain the ceramic layers of thickness from 1 micron upwards on top of the hard metal; ii) maintaining the flow rate of these gases from 1 1t/min to 60 1ts/min and the hard metal in addition to tungsten carbide and the binder phase contains alloying carbides and nitrides not less than 1%. 2. The method as claimed in claim 1, wherein the product obtained is a multi- phased coatings with binder, on the surface of hard metal. 3. The method as claimed in claim 1, wherein the coating induces less brittleness to the coated carbide. 4. The method as claimed in claim 1, wherein the coating produces better adhesion/bond between the substrate and the surface layers.

Full Text

The invention is about the process of sinter coating for the formation of wear resistant layers on hard metals in the sintering process.
PRESENT STATE OF THE ART:
The wear resistant surface layers are composed of ceramic carbides / carbo-nitrides / borides and can be formed either as individual layers of carbides or nitrides etc or as a combination of all. The binder content in the ceramic layers varies from 0% to 30% mass. The hard metal substrates contain 95% to 75% wear resistant material with the binder made of cobalt/nickel/molybdenum/aluminium varying from 5% to 25% mass.
As per know technology ceramic layer coatings of high wear-resistance are obtained on hard metals primarily in two stages:
Sintering of hard metals in which green compacts are subjected to heat treatment (sintering) either under vacuum or a reducing/inert atmosphere to obtain the sintered hard metal.
Subsequently, coating processes like CVD, PVD, PACVD, MTCVD, etc are employed wherein the sintered hard metal is subjected to deposition of different ceramic compounds on the surface of the hard metal either through a chemical process or ionic process.
LIMITATIONS:
In the above mentioned methods:
Cost is high due to a separate post-sintering coating operation. No metallurgical bond between the ceramic coating and the hard metal substrate leading to limitations in coating adhesion. - The coatings are always pure ceramic layers with no options for the formation of multiphase ceramic layers with a binder, resulting in brittle coatings.

OBJECT OF THE PRESENT INVENTION:
The aim of the present invention is to get a ceramic coating on hard metal at low cost, with a better bond between the coating and the substrate and to reduce the brittleness of the coated layers by producing the coating in the sintering process.
It is a functionally gradient material wherein the surface layers are more wear resistant than the remaining portion of the hardmetal tool.
Functionally in a metal cutting application, the surface of the tool needs to be more wear resistant to improve the cutting process. In the conventional Hardmetal cutting tool, selective hardening of the surface is not possible.
In the conventional tool, a stand-alone process called the CVD or Chemical Vapour Deposition technique is adapted to deposit ceramic coatings on hard metal tools to improve the surface hardness or wear resistance. But in the new process the entire selective hardening is carried out in the process of consolidation or sintering, chemicals are not used unlike CVD and so the process for the present invention is Bio-friendly. More economical as CVD is a costly process. Since the basic hard metal itself is tailored to get the surface layers of high wear resistance, the bond between the layers and the tool is strong.
In CVD, the layers deposited are external and the bonding strength with parent hard metal has its limitation.
DETAILED DESCRIPTION:
During the normal sintering cycle at varying pressures from 0.02 mbar to 100 mbar different active gases like methane, hydrogen, carbon monoxide, argon and nifrogen are used in combination with vacuum (0.003 mbar to 0.5 mbar) at different temperature ranges from 500 degrees C to 1600 degree C to obtain the ceramic layers of thickness from 1 micron upwards on top of the hard metal. The flow rate of these

OBJECT OF THE PRESENT INVENTION:
The aim of the present invention is to get a ceramic coating on hard metal at low cost, with a better bond between the coating and the substrate and to reduce the brittleness of the coated layers by producing the coating in the sintering process.
It is a functionally gradient material wherein the surface layers are more wear resistant than the remaining portion of the hardmetal tool.
Functionally in a metal cutting application, the surface of the tool needs to be more wear resistant to improve the cutting process. In the conventional Hardmetal cutting tool, selective hardening of the surface is not possible.
In the conventional tool, a stand-alone process called the CVD or Chemical Vapour Deposition technique is adapted to deposit ceramic coatings on hard metal tools to improve the surface hardness or wear resistance. But in the new process the entire selective hardening is carried out in the process of consolidation or sintering, chemicals are not used unlike CVD and so the process for the present invention is Bio-friendly. More economical as CVD is a costly process. Since the basic hard metal itself is tailored to get the surface layers of high wear resistance, the bond between the layers and the tool is strong.
In CVD, the layers deposited are external and the bonding strength with parent hard metal has its limitation.
DETAILED DESCRIPTION:
During the normal sintering cycle at varying pressures from 0.02 mbar to 100 mbar different active gases like methane, hydrogen, carbon monoxide, argon and nitrogen are used in combination with vacuum (0.003 mbar to 0.5 mbar) at different temperature ranges from 500 degrees C to 1600 degree C to obtain the ceramic layers of thickness from 1 micron upwards on top of the hard metal. The flow rate of these

gases vary from 1 It/min to 60 Its/min. The hard metal in addition to tungsten carbide and the binder phase contains alloying carbides and nitrides not less than 1%.
Hard metals contain a uniform mixture of varying levels of tungsten carbide (WC), hard & wear resistant ceramic carbides and nitrides of the elements of Group: IV B and V B of the periodic table like titanium, tantalum, zirconium and others along with the soft elements of the GroupVIII like cobalt, nickel and others.
In the powder metallurgy of hard metals, the powder mixtures containing all these compounds & elements are compacted known as the green compacts. Green compacts are soft and contain high level of porosity, which is removed in the subsequent process called sintering. Sintering consolidates the green compacts removing all the pores and makes the hard metals hard. It also results in uniform distribution of all the phases containing the carbides and nitrides and the soft metals. This results in isotropic characteristics.
In the new process, the carbides and nitrides of the elements of Group: IV B and V B are made to migrate to the surface of the hard metals during sintering, to form layers of these compounds. These compounds impart high wear resistant property to the surface of hard metals. This migration is effected using special gases like methane, hydrogen, argon and necessarily nitrogen. The quantum of migration depends on the process conditions like the partial pressures of these gases, temperature ranges and the basic composition of the hard metals and the quantum of migration affects the extent wear resistance obtained at the surface.

WE CLAIM:
1. A method of sinter coating for the formation of wear resistant layers on hard metal comprising the step of:
i) sintering of the hard metal at varying pressures from 0.02 mbar to 100 mbar different active gases like methane, hydrogen, carbon monoxide, argon and nitrogen in combination with vacuum (0.003 mbar to 0.5 mbar) at different temperature ranges from 500 degrees C to 1600 degree C to obtain the ceramic layers of thickness from 1 micron upwards on top of the hard metal;
ii) maintaining the flow rate of these gases from 1 1t/min to 60 1ts/min and the hard metal in addition to tungsten carbide and the binder phase contains alloying carbides and nitrides not less than 1%.
2. The method as claimed in claim 1, wherein the product obtained is a multi-
phased coatings with binder, on the surface of hard metal.
3. The method as claimed in claim 1, wherein the coating induces less brittleness
to the coated carbide.
4. The method as claimed in claim 1, wherein the coating produces better
adhesion/bond between the substrate and the surface layers.

Documents:

1605-mas-1996 abstract duplicate.pdf

1605-mas-1996 abstract.pdf

1605-mas-1996 claims duplicate.pdf

1605-mas-1996 claims.pdf

1605-mas-1996 correspondence others.pdf

1605-mas-1996 correspondence po.pdf

1605-mas-1996 description (complete) duplicate.pdf

1605-mas-1996 description (complete).pdf

1605-mas-1996 form-1.pdf

1605-mas-1996 form-26.pdf

1605-mas-1996 form-4.pdf

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Patent Number

198374

Indian Patent Application Number

1605/MAS/1996

PG Journal Number

20/2006

Publication Date

19-May-2006

Grant Date

20-Jan-2006

Date of Filing

13-Sep-1996

Name of Patentee

M/S. WIDIA (INDIA) LTD

Applicant Address

8/9th mile, tumkur road, post bag 7300, bangalore 560 073

Inventors:

#	Inventor's Name	Inventor's Address
1	MR. RAGHAVAN RENGARAJAN,	C.O M/S WIDAIA LTD, 8/9TH MILE, TUMKUR ROAD, POST BAG 7300,BANGALORE- 560 073
2	MR. PASUPULATI TULSIRAM VASANTH KAMAR,	C.O M/S WIDAIA LTD, 8/9TH MILE, TUMKUR ROAD, POST BAG 7300,BANGALORE- 560 073
3	MR. DEVANATHAN SARATHY	C.O M/S WIDAIA LTD, 8/9TH MILE, TUMKUR ROAD, POST BAG 7300,BANGALORE- 560 073

PCT International Classification Number

C048 35/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA