Rapid thermal processing of TiN coatings deposited by chemical and physical vapor deposition using a low-energy, high-cu
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I. INTRODUCTION
THE high level of compressive residual stress in TiN coatings deposited by physical vapor deposition (PVD) methods, of the order of 4.5 GPa, is well established,[1,2] and the availability of a posttreatment to reduce this stress is desirable because it can lead to early coating detachment in use. A possiblity of using rapid thermal processing (RTP) for this purpose is offered by pulsed intense ion or electron beams. The general applications of this treatment to materials have been reviewed[3–8] and indicate that this may prove to be a viable approach. The pulsed melting of a surface followed by extremely rapid cooling of the order of 109K?s21 (103 K in a ms) produces very fine-grained material often with a modified element distribution in the case of metallic alloys. The effects are not confined to the fused zone, however, and changes in the microstructure and hardness of treated steels have been recorded down to depths of many tens of microns.[6,7] ANTHONY J. PERRY, Consultant, is with AIMS Marketing, San Diego, CA 92127. JESSE N. MATOSSIAN, Research Project Manager, JOHN J. VAJO, Senior Research Staff Chemist, and ROBERT E. DOTY, Research Staff Member, are with HRL Laboratories, Malibu, CA 90265-4799. STEVE J. BULL, Reader in Surface Engineering, and TREVOR F. PAGE, Cookson Group Professor of Engineering Materials, are with the Materials Division, Department of Mechanical, Materials and Manufacturing Engineering, University of Newcastle, Newcastle-upon-Tyne NE1 7RU, England. DMITRI I. PROSKUROVSKY, Professor and Head, VLADIMIR P. ROTSHTEIN, Senior Researcher, and ALEXEY B. MARKOV, Researcher, are with the High Current Electronics Institute, Russian Academy of Sciences, Siberian Division, 634055 Tomsk, Russia. PETER C. RICE-EVANS, Professor of Physics, and JAMES TAYLOR, Graduate Student, are with Royal Halloway, University of London, Egham, Surrey TW20 0EX, England. DANIEL E. GEIST, Director of Operations, is with Analytical Reference Materials International, Evergreen, CO 80439-2246. Manuscript submitted March 2, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS A
In contrast, TiN coatings deposited by chemical vapor deposition (CVD) methods are under a low tensile residual stress, of the order of 0.5 to 1.0 GPa.[9] The CVD process operates at about 950 8C without plasma so that the resulting residual stress is only caused by differential thermal contraction with respect to the substrate. Such tensile stresses can promote through-thickness cracking and chipping of the coating, which can deleteriously affect the service performance. Thus, any technique that produces lower stress or stress-free material can offer practical advantages. In the present work, the effects of a low-energy, highcurrent electron beam (LEHCEB) treatment[6,7,8] on TiN coatings deposited by CVD and PVD, respectively, have been studied. The energy levels chosen of 3, 4, and 5 J?cm22 were high relative to conventional ion-assisted PVD technology (1 J 5 6.24 3 1018 eV) and were based on previous extensive[6–8,10] (and unpublished)
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