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This invent!on relates to past sintered WC cutting tools, such as, far instance, drills, and a method of manufacture thereof.
Heating by microwaves is volumetric, induced by interaction with material, selective and environmental friendly. This invention relates to microwave treatment of cemented carbide tools far performance enhancement. The advent of a class of high strength materials for high performance application poses constraints in selection of cutting tools; treatments include cryogenic treatment and vapour deposition. Cryogenic treatment is related to micro-structural ingredients, wh ile surface coatings have to meet the requirement of tenacity and substrate characteristics.
This invention lays emphasis on microwave assisted post-sintering treatment of cemented carbide drill inserts for enhancement of drilling performance. Response of VIC inserts to microwave i rradiation resulted in enhanced metallurgical and mechanical propert ies of inserts, facilitating improved machining performance.
Cemented tungsten carbide iWC) drilling tool inserts (K-20) subjected to post sintering treatment by microwave irradiation exhibit improved cutting
performance.
The method of manufacture of a post sintered WC cutting tool, according to this invention, comprises the steps of sub j ecting a sintered WC cutting tool to microuiave treatment in a mult imode resonator at a frequency of of 2.45 GHz for a duration of 1SCH3 seconds the microwave reflecting part of the said tool being insulated by a microwave transparent material, and the microwave irradiation being concentrated tosuards the tip of the said cutting tool.
This invention will now be described with reference to the accomp anying drawings by way of illustrat ion, and not by way of limitation, wherein
Figs. 1(a) to 1(e) illustrate typical optical and SEM micrographs of cemented carbide microwave treated
Figs. 2(a) &• 2
Fig.3. illustrates variation in hardness (Vickers) before and after microwave treatment
Fig.4. illustrates cutting force variation for with and wi thout microwave treatment of cemented carbide drill inserts
Fig.5. illustrates effect of microwave treatment on tool wear of cemented carbide drill inserts
and
Fig.6. illustrates effect of microwave treatment on hole deviation of cemented carbide drill inserts
EXAMPLE
Cemented WC drill inserts of compos i t ion (WC-S0'/, and the rest with major of Cobalt (Co) and other minor elements) were subjected to microwave post sintering treatment in a ir.uit imode resonator (2.45 GHz) for an effective micro wave caupl ing duration of 1S00 seconds. Reflection of microwaves by mic rowave reflectors (metals) may damage the microwave source itself and hence reflecting part (shank portion) of the cutting tool has been effectively insulated by a microwave transparent material(alumina), and thereby microwave irradiation is concentrated toward drill tip. Changes
in properties (metallurgical and mechanical) owing to microwave treatment were assessed through opt ic al microscopy, SEM and hardness survey (Vickers). Machining performance of the inserts was evaluated through drilling of glass reinforced polymeric composi te. Microwave irradiated inserts exhibited superior performance over the non-treated tools.
Plain cemented carbide drill inserts consists of WC and Co. WC is absorber of microwaves. Micro-structural and phase changes have been facilitated due to microwave irradiation. Typ ical micrographs of microwave treated and untreated cemented carbide inserts are presented in Figs.1(a) to 1(e). Compared to the untreated, more cemented carbide grains can be seen over the treated surfaces due to depletion of surface Co resulting in cemented carbide grain upliftment and formation of WC skeleton matri>:. XRD profile (Fig.2) of treated cutting inserts consists of WC, W«C and camp leu compound namely Co* W* C. Th is compi en carbide format ion increases the hardness of tools from the range of 1375-1525 Kg/mm to the range of 1700-1900 Kg/mm (Fig.3).
Thus post sintering treatment using microwave irradiation on cemented carbide drill inserts has
yi elded micro structural, phase changes and improved hardness. Significance of microwave treatment on variation of drilling force is illust rated in Fi gs.4
During machining of heterogeneous materials such as cast i ron and composi te, cutting tools are often sub jected to force variations due to encounter wi th the soft and hard phases of work material. Such variation in cutting force results in reduced tool life due to increased tool wear. Comparat ively tool wear of treated tools with number of holes is of lower order as seen in Fig,5. Comb ination of relatively softer bulk and harder surface of the treated Inserts due to microwave post sintering treatment has given adequate strength to the cutting insert to accommodate the fluctuation of cutting forces, during machining of heterogeneous material possibly accounting for the enhancement of tool life. Quality of the holes produced in the g1 ass re inforeed polymeric composi te is
also an important parameter. Hoie deviation as sac i ated with delamination can affect the strength. Fiber pull out, matrix crazing and deviation of hole size at the entrance and exit are same majar problems encountered during drilling of composi tes. Hole deviation is measured using Angus vision system and the details are presented in the Fig.6. The holes produced by the microwave treated tools exhibited lower amount of deviat ion.
Microwave post sintering treatment on cemented carbide cutt ing tools has resulted in visible improvements in metallurgical and mechanical propert i es. Microwave treatment is associated with environmental friendly nature and low order cost. Reduced order of cutting forces, increased tool life and improved quality of the hoi es produced are attractive features assoc iated with the microwave treated tools.
The terms and expressions in this specification are of
description and not of limitation, since such terms and
expressions do not exclude any equivalents of the
features illustrated and described, having regard to
the scope and ambit of this invention.
We Claim:
1. A method of manufacture of a post sintered WC cutting tool comprising the steps of subjecting a sintered WC cutting tool to microwave treatment in a multimode resonator at a frequency of 2.45 GHz for a duration of 1800 seconds, the microwave reflecting part of the said tool being insulated by a microwave transparent material and the microwave irradiation being concentrated towards the tip of said cutting tool.
2. A method as claimed in Claim 1 wherein the cutting toot is a drill and the shank portion thereof is insulated by a microwave transparent material.
3. A method of manufacture of a post sintered WC cutting tool substantially as herein described with reference to and as illustrated in the accompanying drawings.
4. A post sintered WC cutting tool whenever manufactured by a method as claimed in any one of the preceding Claims
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