Materials Performance

JUN 2019

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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35 MATERIALS PERFORMANCE: VOL. 58, NO. 6 JUNE 2019 defects increased, and therefore, the corro- sion protection of the coating decreased. Liu, et al., 4 reported that a CrN PVD coating placed onto a steel substrate polished with 6-µm diamond paste provided significantly better corrosion protection than similar coatings deposited onto rougher substrates, while Phygen recommends that the sub- strate surface be as smooth as practical to optimize corrosion resistance using the APA process, with a super-fine finish of <0.2 µ m being optimum. Several authors have reported that nitriding of a substrate prior to the applica- tion of a PVD coating, which is referred to as a duplex treatment, increases substrate hardness and corrosion resistance. 2,6 Nitrid- ing involves the diffusion of atomic nitrogen into the surface of the steel to create a hard surface layer. Nitriding can be performed in several ways—using a gaseous or liquid s ourc e of nitrogen or v i a pl asma ion nitriding. Fenker, et al., 5 confirmed that duplex treatments of nitriding plus PVD coating can provide enhanced corrosion protection, but they suggested that conventional nitrid- ing treatments, such as gas or liquid nitrid- ing, might provide better corrosion protec- tion than a nitride layer produced by plasma nitriding. Summary In summar y, laborator y studies and comm ercial applications have demon- strated that PVD thin-film coatings can pro- vide excellent corrosion protection to metal substrates, as long as the defect content in the coating is kept low. The APA process is one PVD technique that is capable of pro- ducing coatings with extremely low levels of defects, and testing by the U.S. Army has demonstrated that it can outperform con- ventional chromium treatments. References 1 C.P. Mulligan, et al., "CrN, CrN/SiC, and CrN/ DLC Coatings Deposited by a Novel Arc Plasma Acceleration Process: Processing and Properties," Materials and Manufactur- ing Processes 29 (2014): pp. 1,037-1,043. 2 N. Dingremont, et al., "Comparison of the Corrosion Resi stance of D if ferent St eel G r a d e s N i t r i d e d , C o a t e d a n d D u p l e x Treated," Surface and Coatings Technolog y 76-77 (1995): pp. 218-224. 3 J. Aromaa, et al., "Identification of Factors Af- fecting the Aqueous Corrosion Properties of (Ti, Al) N-Coated Steel," Surface and Coatings Technology 49 (1991): pp. 353-358. 4 C. Liu, et al., "An A.C. Impedance Study on PVD CrN-Coated Mild Steel with Different Surface Roughness," Surface and Coatings Technology 76-77 (1995): pp. 623-631. 5 M. Fenker, M. Balzer, H. Kappl, "Corrosion Protection with Hard Coatings on Steel: Past Approaches and Current Research Efforts," Surface and Coatings Technolog y 257 (2014): pp. 182-205. 6 O. Durst, J. Ellermeier, C. Berger, "Influence of Plasma-Nitriding and Surface Roughness on the Wear and Corrosion Resistance of Thin Film (PVD/PECVD)," Surface and Coat- ings Technology 203 (2008): pp. 848-854. 7 V.N. Khominich, "Cathode Arc Vapor Deposi- tion Method and Apparatus," U.S. Patent 6,103,074, 2000. 8 AMS2460A. "Plating, Chromium" (Warren- dale, PA: SAE International, 2013). 9 AMS2404H. "Plating, Electroless Nickel" (Warrendale, PA: SAE International, 2017). 10 GM9540P. "Ac c el erat ed C orro sion Te st " (Detroit, MI: General Motors Corp., 1997). 11 A.P. Ehiasarian, et al., "High Power Pulsed Magnetron Sputtered CrNx Films," Surface and Coatings Technolog y 163-164 (2003): pp. 267-272. 12 Y.P. Purandare, A.P. Ehiasarian, P.Eh. Hovese- pian, "Deposition of Nanoscale Multilayer CrN/NbN Physical Vapor Deposition Coat- ings by High Power Impulse Magnetron Sputtering," J. Vac. Sci. Technol. A 26, 2 (2008): pp. 288-296. FIGURE 5 Photographs of the APA process CrN-coated spindle, (a) and (b), and the legacy Cr-plated spindle, (c) and (d), following extensive live fire and accelerated corrosion testing. 13 D. Lafontaine, "Improved Coating for Howit- zer Spindles to Save Money, Reduce Environ- m ent al Imp act," www.army.mi l/ar ticl e/ 123063/improved_coating_for_howitzer_ s p i n d l e s _ t o _ s a v e _ m o n e y _ r e d u c e _ environmental_impact (April 4, 2014). DAVID C. BELL is president and CEO of Phy- gen Coatings, Inc., Minneapolis, Minnesota, USA, email: david.bell@hygen.com. He has been a pioneer in the use of PVD coatings, introducing them to U.S. markets over 30 years ago. He founded Phygen in 1994, based on the advanced technology of the plasma acceleration PVD process. VIKTOR KHOMINICH is chief scientist at Phy- gen Coatings, Inc., Minneapolis, Minnesota, USA, email: vkhominich@phygen.com. He has over 35 years of experience in research and development of processes and equipment for surface modification and for coating deposi- tion in a vacuum by using high-density, mag- netically enhanced arc plasma. Khominich invented a process and a device for the arc plasma acceleration by magnetic field to pro- duce high-quality industrial coatings that have been commercially successful in combat- ing abrasive wear, erosion, and corrosion of metals (U.S. Patent 6,103,074). STEVE MIDSON is president of The Midson Group, Denver, Colorado, USA, email: Steve@ TheMidsonGroup.com. He holds a Ph.D. in metallurgy from University of Sheffield (U.K.). Midson is working to apply PVD coatings in various applications, including corrosion pro- tection and to attend the life of metal shaping tools. CHRISTOPHER MULLIGAN is a senior materi- als engineer and CCDC Armaments Center technical lead for surface technologies and wear/corrosion of materials at the U.S. Army Armament Research, Development, and Engi- neering Center—Benét Laboratories, Waterv- liet, New York, USA. Mulligan holds a Ph.D. in materials science and engineering from Rens- selaer Polytechnic Institute. High-Quality Physical Vapor Deposition Coatings for Corrosion Protection Applications

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