QQC Diamond Coating Unit 90

Objectives Define the role of diamonds in industrial applications Compare the HP/HT and CVD processes Describe the QQC process and summarize the steps in the process Provide QQC applications and describe the benefits of diamond coating of tooling and machinery components Discuss diamondlike carbon (DLC) and its main application

QQC Deposits uniform layer of diamond on almost any type of material ranging from glass and plastic to metals Uses carbon dioxide from air as carbon source Subjects it to combination of lasers Can do in seconds what takes CVD hours

Diamond Tool Development Diamond-tipped precision lathe tools used by J. Ramsden in 1771 Diamond wire-drawing die patent (English) granted to William Brockendon in 1819 Large, circular saw blades were set with diamonds around 1900 Continued development dramatic and in 1950s, General Electric Co developed high-temperature, high-pressure process to manufacture diamonds

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HP/HT Synthesis Process Requires pressures of 1 million pounds per square inch and temperatures of about 2000ºF in presence of metal catalysts Requires more steps to be made into useful tools and products Coating must be bonded to saws and grinding wheels by resin, impregnation, or plating

HP/HT Synthesis Process For cutting tools, diamond powder sintered to tungsten carbide substrate, then cut into shapes that are brazed to tool bodies or inserts Ground to finished size and shape Applications to geometrical shapes severely limited Labor-intensive and costly fabrication

Chemical Vapor Deposition (CVD) Process Produce atomic hydrogen from diatomic hydrogen molecule Gaseous hydrocarbon source mixed with hydrogen and passed over substrate Diamond condenses and falls onto substrate as crystals, which fuse into polycrystalline layer

Diamond Characteristics Properties due to short, strong bonds between its carbon atoms Hardest known material Highest thermal conductivity Highest electronic mobility Highest sound velocity Highest transparency near visible region Ideal material for coating parts subject to sliding friction

Limitations Still relatively expensive CVD process still batch processing method May take 24 hours or more for coating Deposition rates range from 1-5 micron/hr Substrate must be thoroughly cleaned and preheated in vacuum chamber Restricted to limited substrate chemistry

Diamond Coating Breakthrough Major breakthrough in diamond deposition technology by Pravin Mistry, metallurgist Research of laser synthesis of titanium diboride Mistry switched carbon dioxide for nitrogen Produced coating speckled with black particulate inclusions Analysis indicated presence of polycrystalline diamond

QQC Process Laser energy directed at substrate to mobilize, vaporize, and react primary element contained within substrate (carbon) Changes composition of basic elements and diffuses modified constituent back into part, as addition to fabricating coating Creates conversion zone immediately beneath substrate and results in diffusion bonding

Additional similar or different elements may be introduced in reaction zone Expand fabrication and composition of coating Laser energy provided by combination of lasers: excimer, Nd:YAG, and CO2 Output beams directed through nozzle delivering secondary element Reaction zone shielded by inert gas Flat plasma created by lasers, constituent element and secondary element on surface and extends around edges

Diamond Coating Object to be coated can be moved around by robotic arm Under laser which controls deposition of diamond Adjustment of lasers can control crystal size and structure Most synthetic diamond made by CVD Still coat only a few and requires vacuum chamber heated to 800ºC

Diamond Thickness Thickest layer of diamond by QQC process has been 1000 microns Forms at rate of about 1 micron per second Bonds metallurgically to surface below Thickest layer created by CVD has been 22 microns Forms at rate of a few microns per hour

Field Tests Claims Tools coated both in diamond and in TNC (tetrahedrally bonded noncrystalline carbon) used for power train and chassis components Gears, shock-rods, struts, and brake rotors In some cases to replace chromium plating QQC coated tools best in terms of performance, wear and adherence on carbide tool inserts

Key Advantages of QQC Process Superior adhesion and reduced interfacial stress result from graded metallurgical bond between diamond and part Process carried out without restrictions of vacuum chamber Pretreatment and/or preheating of substrate not required Elimination of wet chemistry pretreatment

Deposition rates dramatically increased Only carbon dioxide used as primary/secondary source for carbon with nitrogen acting as shield and stoichiometric process ingredient Replace use of dangerous gages Deposition rates dramatically increased Linear growth rates exceeding 1 micron per second (1-5 microns per hour by CVD) Process can be applied to almost any substrate

Multiplexed laser process can accommodate any percentage of cobalt without affecting diamond synthesis Process can be changed automatically to control crystal size, orientation, and morphology System production engineered to permit economical coating of production components with 24 hour unmanned operation

Diamondlike Carbon (DLC) Near relative of diamond Tetrahedrally bonded noncrystalline diamond (TNC) Shows many of the desirable properties of diamond but may contain some weaker bonds Ideal material for supplementing chromium plating

Looking Ahead Cubic boron nitride (CBN) preferred cutting-tool coating material for machining cast iron Superlattice material with crystal morphology similar to diamond's Cutting-tool market growing for CBN Managed to synthesize pure and composite CBN on tungsten carbide inserts using lasers

Cutting-Tool Technology Diamond cutting tools provided major benefits for machining aluminum alloys QQC's diamond deposition process provides cost-effective, high performance dry machining capability Diamond coating can be deposited on variety of shapes

Diamond Coating Technology QQC Revolutionary, proprietary process for high-speed diamond deposition on variety of substrates Metallurgically bonded to substrates Proving to be final key for advanced dry machining of aluminum alloys Benefits: Increased production speeds, high product quality and elimination of coolants