Title of Invention

A SPROCKET COMPONENT FOR TWO WHEELERS AND THE PROCESS OF ITS MANUFACTURE

Abstract

The present invention relates to a Sprocket for two wheelers, having a high surface wear resistance characteristics, with an enhanced level of carbon content on its surface thereby providing a Martensite structure, as a result of treatment of the Sprocket in an enriched carbon atmosphere; the penetration of carbon extending to about 2mm below the surface of the Sprocket; and said Sprocket having a Bainite and Martensite core having more core toughness than the surface of said Sprocket; the Sprocket comprising Chromium 2-4% + Molybdenum 0.3-1.0% along with 0.2-0.8% of Carbon in the form of Graphite Powder by weight and the remaining Iron; and a process for the manufacture of a Sprocket for use in two wheelers.

Full Text

FIELD OF INVENTION The present invention provides for Powder Metallurgy Sprocket component used in two wheelers, comprising an enhanced level of carbon content on its surface having a Martensite microstructure with Bainite and Martensite microstructure in the core. The present invention also provides for a process for the manufacture of said sprocket. BACKGROUND AND PRIOR ART REFERENCES Many powder metallurgy components are used in application where they come in contact with other moving parts. Under these conditions, surface wear resistance is an important property, which the components must possess to perform well during application and with good core toughness. To achieve the dual properties, generally the PM components are heat treated in equipment such as a Sealed Quench Furnace after sintering the components. One disadvantage with such a process is the cost involved for the extra operation. The other disadvantage is that, the components are quenched in oil after astonishing them and this causes distortion in the component. Hence, such components require further expensive operations such as grinding to meet the final pre-determined dimensions resulting in cost escalation. An alternative method, which is currently coming in vogue, is Sinter Hardening. In this method, hardening is achieved by increasing the alloying elements such as Ni, Cr, Mo, Mn and Cu in the PM components and forced cooling the parts to room temperature after sintering. The cooling rate is increased by improving heat transfer; either by increasing the volume flow of gas or by having improved cooling through an annular water cooling jacket. The equipment is expensive and addition of metals such as Mo escalates part cost. By this process the parts are hardened throughout the section of the component as against case hardening which is ideally suited for application involving moving parts. In the prior art mentioned above, two separate furnaces are used; one for sintering and other for re-heating and oil quenching the parts. Patent Application US 4,106,931 deals with an alternative protective gas based on nitrogen based atmospheres to prevent and or minimise surface decarburization, reduce additions of hydrocarbons and methods thereby to sinter products in this atmosphere. The carbon intrusion by this method is in the Hot Zone. This patent application US 4,106,931 uses only general ferrous materials. REFERENCES: 1. Astaloy CrM: New generation powder from Hoganas, Powder Metallurgy, 1998, Vol41,No4,pp 232-233, 2. A.B.Davala, A.H.Graham, R.J.Causton. Effect of process Conditions upon Sinter-hardening Response of PM Alloy PLC-4608. Industrial heating, September 1998, pp 111-120. 3. J.M. Capus. Sinter hardening offers high strength at lower cost. Metal Powder Report, September, 1997 pp 17-18 4. C. Lindberg, U. Engstrom, P. Endel. Sintered High strength materials.(pM-7). Private Publication, ppl-8. 5. F.Chagnon, Y. Trudel. Designing Low Alloy Steel Powders For Sinter hardening Applications. Private Publication pp 1-10. 6. D. Warga, C. Lindberg. Efficient Sintering and Hardening in the Conveyor belt sintering furnace. Proceedings of 1993 Powder Metallurgy World Congress, Part-2. pp 983-986. 7. Howard Ferguson. Guidelines for Heat Treating Powdered Metal Parts. ASM, The Heat Treating Source Book 1986, pp 162-167. 8. P. Johnson, W.Q. Judge and H.S. Nayar. Microstructures, quality control of P/M parts heat treated under various atmospheres. ASM, The Heat Treating Source Book 1986, pp 168-174 OBJECTS OF THE INVENTION The main object of the present invention is to provide for a Sprocket component comprising an enhanced level of carbon content on its surface having Martensite microstructure having high surface wear resistance with Bainite and Martensite structure in the core for good core toughness. The present invention also provides for a process for the manufacture of said Sprocket. Another object of the present invention is to manufacture a Sprocket for use in two wheelers with a substantial Martensite microstructure on the surface. Yet another object of the present invention is to have a Bainite and Martensite microstructure in the core of the Sprocket. Still another object of the invention relates to manufacture of components requiring good surface wear characteristics using similar materials and process. Further another object of the present invention, wherein Bainite and Martensite structure in the core of the Sprocket is having more toughness than the surface. STATEMENT OF THE INVENTION: The present invention relates to a Sprocket for two wheelers, having a high surface wear resistance characteristics, with an enhanced level of carbon content on its surface thereby providing a Martensite structure, as a result of treatment of the Sprocket in an enriched carbon atmosphere; the penetration of carbon extending to about 2mm below the surface of the Sprocket; and said Sprocket having a Bainite and Martensite core having more core toughness than the surface of said Sprocket; the Sprocket comprising Chromium 2-4% + Molybdenum 0.3-1.0% along with 0.2-0.8% of Carbon in the form of Graphite Powder by weight and the remaining Iron; and a process for the manufacture of a Sprocket for use in two wheelers, said process comprising: (i)providing a suitable die and filling the die with alloy powder material Chromium 2-4% + Molybdenum 0.3-1.0% along with 0.2-0.8% of Carbon in the form of Graphite Powder by weight and the remaining Iron; (ii) compacting the powder material to achieve the pre-determined shape of the Sprocket using suitable tooling comprising die, punches and core rods; (iii)sintering the compacted sprocket in a N2-H2 atmosphere at a constant high temperature; (iv) treating the sintered sprocket in the cooling zone of the furnace; (v) enriching the cooling zone with carbon containing gases; (vi) diffusion of carbon content on the surface for the creation of Martensite structure of the said Sprocket; and (vii) creating an interior Bainite and Martensite microstructure having more core toughness. SUMMARY OF THE INVENTION The present invention provides for a Sprocket having high surface wear resistance and good core toughness. The present invention also provides for a process to sinter low carbon PM component Sprocket and enrich the components immediately after sintering by providing an atmosphere, which is rich in carbon. Carbon enrichment of the atmosphere enhances the carbon level on the surface of the part. This ensures a surface with high wear resistance and a core with a lower carbon having more toughness than the surface. DETAILED DESCRIPTION OF THE INVENTION Accordingly, the present invention provides for a novel Sprocket for two wheelers, having a high surface wear resistance characteristics, with an enhanced level of carbon content on its surface thereby providing a Martensite structure, as a result of treatment of the Sprocket in an enriched carbon atmosphere; the penetration of carbon extending to about 2mm below the surface of the Sprocket; and said Sprocket having a Bainite core having more core toughness than the surface of said Sprocket; the Sprocket comprising Chromium 2-4% + Molybdenum 0.3-1.0% along with 0.2-0.8% of Carbon in the form of Graphite Powder by weight and the remaining Iron; An embodiment of the present invention, wherein the Sprocket comprising martensitic microstructure on the surface with a thickness in the range Another embodiment of the present invention, wherein the Sprocket comprises 0.2 to 0.5 % of Carbon In the core resulting in Bainite and Martensite microstructure having good core toughness. Yet another embodiment of the present invention, wherein the Bainite and Martensite microstructure at the core the Sprocket has more toughness than that of the surface of the Sprocket. Still another embodiment of the present invention, wherein the core hardness thus achieved is the range of 200 to 300 HV, O.I. Further another embodiment of the present invention, wherein the surface hardness thus achieved is about 400 HV 0.1. Yet another embodiment of the present invention, wherein said Sprocket has a reduced distortion property requiring no corrective measures. The present invention also provides for a novel process for the manufacture of said Sprocket for use in two wheelers, said process comprising; (i) providing a suitable die and filling the die with alloy powder material comprising Chromium 2-4% + Molybdenum 0.3-1.0% along with 0.2-0.8% of Carbon in the form of Graphite Powder by weight and the remaining Iron; (ii) compacting the powder material to achieve the pre-determined shape of the Sprocket using suitable tooling comprising die, punches and core rods; (iii) sintering the compacted sprocket in a N2-H2 atmosphere at a constant high temperature; (iv) treating the sintered sprocket in the cooling zone of the furnace; (v) enriching the cooling zone with carbon containing gases; (vi) diffusion of carbon content on the surface for the creation of Martensite structure of the said Sprocket; and (vii) creating an interior Bainite and Martensite microstructure having more core toughness. An embodiment of the present invention, wherein sintering of said Sprocket is at an elevated temperature of about 1120 °C for about 45 minutes. o Another embodiment of the present invention, wherein said N2-H2 gas Protective Gas atmosphere comprises about 70% Nitrogen and about 30% Hydrogen gas by volume. Yet another embodiment of the present invention, wherein the desired level of Hydrogen is increased to a maximum of about 75%, as a result of fully dissociated ammonia gas. Still another embodiment of the present invention, wherein the said hydrocarbon gas is added to maximum 1.5% by volume to the protective gas for carbon enrichment. Yet another embodiment of the present invention, wherein alternative synthetic gases produced from Nitrogen, Methanol are used. Another embodiment of the present invention, wherein minute additions of Hydrocarbon gases, selected from LPG, Propane or Methane that are rich in carbon are used in the cooling zone for Carbon enrichment up to 1.5% by volume. Still, another embodiment of the present invention, wherein cooling rates in the cooling zone is less than 2°C. Yet another embodiment of the present invention, wherein the Sprocket is cooled in annular water-cooled jackets in protective gas atmosphere. Further, another embodiment of the present invention, wherein treating the sintered product in a cooling zone by carbon diffusion by introducing said Hydrocarbon gas at 900 to 800 °C. BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS Figure 1 Depicts Surface microstructure having Martesite formation. Figure 2 Depicts Core microstructure having Bainite and Martensite. ADVANTAGES OF THE PRESENT INVENTION 1. The present invention provides for surface carbon enrichment of products for 7 the purpose of enhancing surface properties of products. 2. The present invention focuses on carbon enrichment in the cooling zone and the distinct phase transformations that occur on the surface and core of the products. The point of carbon intrusion in the furnace is in the cooling zone. 3. The present invention takes advantage of specific materials other than the general ferrous materials used in the prior arts, and carbon enrichment to achieve distinct surface properties like hardness that offers a novel idea whereby, the products can be made using conventional equipment and processes thereby reducing cost of manufacturing. Further, advantages of the present invention over the prior art references are explained below in the form of tables: TABLE 1 COMPARATIVE ACCOUNT OF THE SPROCKET OF THE PRESENT INVENTION WITH THAT OF PRIOR ART SI. No. Heat Treated in Sealed Quench Furnace(SQF) Sinter Harden Route Proposed Method 1 Surface Hardness of 500 to 750 HVO, lean be achieved Surface Hardness of 400 HV 0,1 and better can be achieved Surface Hardness of 400 HV 0,1 and better can be achieved 2 Core Hardness of 200 to 400 HVO, 1 is achieved Core Hardness is same as surface hardness Core Hardness of 200 to 300 HVO, 1 is achieved 3 Surface microstructure is Martensite Surface microstructure is Martensite and or Bainite Surface microstructure is Martensite. (Fig.l) 4 Core microstructure is intermediate structure of Pearlite and Bainite Core microstructure is same as surface microstructure Core microstructure is Bainite and Martensite. (Fig. 2) TABLE 2 COMPARATIVE STEPS FOR THE PROCESS OF THE PRESENT INVENTION AND PRIOR ART SI. No. Heat Treated in Sealed Quench Furnace(SQF) Sinter Harden Route Present invention 1 Powder Ingredients Powder Ingredients Powder Ingredients 3 Critical temperature range 800°C to 500°C Critical temperature range 800°C to 500°C Critical temperature range 800°C to 500°C 4 No enriching hydrocarbon gas during sintering No enriching hydrocarbon gas during sintering Minute additions of LPG or other hydrocarbon gases in temperature range 900°C to 800°C during cooling 5 Raw material cost is about twice as for parts requiring heat treatment in SQF Raw material cost about 20% cheaper than for parts requiring sinter hardening. WE CLAIM: (1) A Sprocket for two wheelers, having a high surface wear resistance characteristics, with an enhanced level of carbon content on its surface thereby providing a Martensite structure, as a result of treatment of the Sprocket in an enriched carbon atmosphere the penetration of carbon extending to about 2mm below the surface of the Sprocket; and said Sprocket having a Bainite and Martensite core having more core toughness than the surface of said Sprocket; the Sprocket comprising Chromium 2-4% + Molybdenum 0.3-1.0% along with 0.2-0.8% of Carbon in the form of Graphite Powder by weight and the remaining Iron. (2) The Sprocket as claimed in claim 1, wherein the Sprocket comprises Martensitic microstructure on the surface with a thickness in the range of 20-200 microns. (3) The Sprocket as claimed in claim 1, wherein the Sprocket comprises 0.2 to 0.5 % of Carbon in the core resulting in Bainite and Martensite microstructure having good core toughness. (4) The Sprocket as claimed in claim 1, wherein the Bainite and Martensite microstructure at the core the Sprocket has more toughness than that of the surface of the Sprocket. (5) The Sprocket as claimed in claim 1, wherein the core hardness thus achieved is in the range of 200 to 300 HV, 0.1. (6) The Sprocket as claimed in claim 1, wherein the surface hardness thus achieved is about 400 HV 0.1. (7) A process for the manufacture of a Sprocket for use in two wheelers, said process comprising: (i) providing a suitable die and filling the die with alloy powder material Chromium 2-4% + Molybdenum 0.3-1.0% along with 0.2-0.8% of Carbon in the form of Graphite Powder by weight and the remaining Iron; 11 (ii) compacting the powder material to achieve the pre-determined shape of the Sprocket using suitable tooling comprising die, punches and core rods; (iii) sintering the compacted sprocket in a N2-H2 atmosphere at a constant high temperature; (iv) treating the sintered sprocket in the cooling zone of the furnace; (v) enriching the cooling zone with carbon containing gases; (vi) diffusion of carbon content on the surface for the creation of Martensite structure of the said Sprocket; and (vii) creating an interior Bainite and Martensite microstructure having more core toughness. (8) The process as claimed in claim 7, wherein sintering of said Sprocket is at an elevated temperature of about 1120 °C for about 45 minutes. (9) The process as claimed in claim 7, wherein said N2-H2 protective gas atmosphere comprises about 70% Nitrogen and about 30% Hydrogen gas by volume. (10) The process as claimed in claim 7, wherein the desired level of Hydrogen is increased to a maximum of about 75%, as a result of fully dissociated ammonia gas. (11) The process as claimed in claim 7, wherein the carbon containing gas is a hydrocarbon gas that is added to a maximum of 1.5% by volume to the protective gas for carbon enrichment. (12) The process as claimed in claim 7, wherein the carbon containing gases are synthetic gases produced from Nitrogen and Methanol for the carbon enrichment. (13) The process as claimed in claim 7, wherein minute additions of Hydrocarbon gases, selected from LPG, Propane or Methane that are rich in carbon are used in the cooling zone for Carbon enrichment up to 1.5% by volume. (14) The process as claimed in claim 7, wherein cooling rates in the cooling zone is less than loc. 12 (15) The process as claimed In claim 7, wherein the Sprocket is cooled in annular water-cooled jackets with protective gas atmosphere. (16) The process as claimed in claim 7, wherein treating the sintered product in a cooling zone by carbon diffusion by introducing said Hydrocarbon gas at 900 to 800°C. (17) The Sprocket for two wheelers, having a high surface wear resistance characteristics substantially as herein described in the examples and in the drawings. (18) The process for the manufacture of a Sprocket for use in two wheelers

Documents:

0889-mas-2001 abstract-duplicate.pdf

0889-mas-2001 abstract.pdf

0889-mas-2001 claims-duplicate.pdf

0889-mas-2001 claims.pdf

0889-mas-2001 correspondence-others.pdf

0889-mas-2001 correspondence-po.pdf

0889-mas-2001 description (complete)-duplicate.pdf

0889-mas-2001 description (complete).pdf

0889-mas-2001 drawings.pdf

0889-mas-2001 form-1.pdf

0889-mas-2001 form-13.pdf

0889-mas-2001 form-19.pdf

0889-mas-2001 form-26.pdf

0889-mas-2001 form-3.pdf

0889-mas-2001 form-5.pdf