Int J Adv Manuf Technol DOI 10.1007/s00170-012-3904-y
ORIGINAL ARTICLE
Laser shock wave treatment of polycrystalline diamond tool and nanodiamond powder compact Cheng Deng & Pal Molian
Received: 26 May 2011 / Accepted: 5 January 2012 # Springer-Verlag London Limited 2012
Abstract Laser shock processing (LSP) of polycrystalline diamond (PCD) tools and nanodiamond powder compacts was conducted using a 1,064-nm Q-switched Nd:YAG laser at peak power densities in the range of 4 to 18 GW/cm2 and pulse repetition rates of 1 to 10 Hz. The PCD tools were directly procured from the tool manufacturer while nanodiamond powder compacts were prepared in the laboratory by cold die press forming and annealing using a powder mixture of nanodiamond, 8 wt.% cobalt, and 10 wt.% agar– agar as the binder. The samples were characterized by Raman spectroscopy, scanning electron microscopy, microindentation, and optical profilometer. Results indicate that LSP induced diamond purification, inhomogeneity of phases in PCD, densification in nanodiamond compact, phase transition to various amounts of sp3 and sp2 carbon forms, and an increase in hardness and surface roughness. Keywords Laser shock processing . Polycrystalline diamond . Nanodiamond . Nd:YAG laser
1 Introduction In recent years, diamond tools are increasingly used in manufacturing of various microdevices as well as in ductile machining of brittle materials. For example, the rapidly growing micro-end milling is a beneficiary of diamond tools with applications in the production of precision biomedical components, micropropellers, microfluidic devices, microheat sinks, microheat exchangers, and X-ray lithography C. Deng : P. Molian (*) Laboratory for Lasers, MEMS and Nanotechnology, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011-2161, USA e-mail:
[email protected]
masks. Single crystalline and polycrystalline diamonds (PCD) as well as chemical vapor deposited (CVD) diamonds are used due to diamond’s attractive properties that include extreme hardness, superior abrasion resistance, high thermal conductivity, high Young’s modulus, low coefficient of friction, and chemical inertness [1–4]. Such properties of diamond enabled to minimize bending, catastrophic failure, and chip adherence of the tools as well as meet the high demands of form accuracy, surface quality, and low subsurface damage of workpiece. There is a huge interest in using nanocrystalline CVD diamond for tools as it offers improved surface finish, lower friction, higher wear, and abrasion resistance and fewer tendencies for cracking over their microcrystalline counterparts [5–7]. Similar results can be expected from the tools made by sintering nanodiamond powders. Nanodiamond, also called nanocrystalline diamond powder, or ultradispersed diamond having a particle size range of 2–20 nm, is considered as a promising material for various applications, including abrasives for the semiconductor and optical industries, durable and hard coatings, additives to lubricants for engines and moving gears, polymer reinforcements, protein adsorbents, and even medicinal drugs. PCD tools have exceptional tool life. Composed of interlocking fine grains, PCD can be considered as an extremely tough composite material formed by sintering diamond particles into a metal matrix (typically cobalt) under high temperature and high pressure [8]. Fine grain diamond (
