Characteristics and properties of cryomilling-induced columnar growth in NiCrAlY coatings on Ni-based superalloy by lase
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Zheng Xiong School of Science, Naval University of Engineering, Wuhan, Hubei 430033, People’s Republic of China
Jinbo Guo and Zhenjie Gu School of Science, Laser Technology Institute, Tianjin Polytechnic University, Tianjin 300387, People’s Republic of China
Xiaoqin Dai School of Computer Science & Software Engineering, Tianjin Polytechnic University, Tianjin, 300387, People’s Republic of China
Chao Yan School of Measuring and Optical Engineering, Nanchang Hangkong University, Nanchang, Jiangxi 330063, People’s Republic of China
Hongbo Panb) School of Engineering Research institute, Anhui University of Technology, Ma’anshan, Anhui 243002, People’s Republic of China (Received 19 January 2016; accepted 28 March 2016)
Cryomilling combined with laser induction hybrid cladding (LIHC) was adopted to produce NiCrAlY coatings on Ni-based superalloy. The characteristics, oxidation resistance, and mechanical properties of the cryomilled NiCrAlY coatings by LIHC were investigated. By increasing the cryomilling time, the as-received spherical powder experienced a transition from flake-shaped to polygonal structure. The particle size increased firstly and then decreased. Moreover, increasing the cryomilling time induced the columnar growth in the NiCrAlY coatings. This in turn improved the oxidation resistance and the mechanical properties of the coatings. Especially, when the cryomilling time was increased to 15 h, the oxidation resistance of the coating at 1423 K was approximately nine times than that of GH4169 superalloy. The tensile strength of the cryomilled (15 h) coating increased to 1085 MPa and the ductility was 20.7%.
I. INTRODUCTION
Contributing Editor: Jürgen Eckert Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2016.162
leading to the spallation in the TGO layer.2 It was therefore crucial to improve the oxidation resistance of MCrAlY coatings to extend their applications in industry. Generally, MCrAlY coatings by plasma spraying exhibited the porosities and micro-cracks. Laser remelting was often adopted to eliminate these defects, and therefore increased the oxidation resistance of MCrAlY coatings.3 Moreover, Al2O3 as the second phase was incorporated dispersedly in MCrAlY coatings to refine the grains of the coatings, which in turn promoted the formation of a protective a-Al2O3 layer.4 Recently, the nanostructured MCrAlY coatings were produced by the combination of high-velocity oxy-fuel (HVOF) and cryomilling.5,6 The nanostructured characteristic of the coating and the presence of Al2O3 within the cryomilled powders had an important effect on the nucleation of the alumina layer. The formation of a continuous TGO layer protected the coating from further oxidation and avoided
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Ó Materials Research Society 2016
Due to preferable oxidation resistance and adjustable chemical composition, MCrAlY (M 5 Ni, Co, or NiCo) coatings were widely used as the protective layer for superalloy and as the bond coat for thermal barrier coatings.1 Alth
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