Preparation of Diamond Reinforced NiCoCrTi 0.5 Nb 0.5 High-Entropy Alloy Coating by Laser Cladding: Microstructure and W
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Preparation of Diamond Reinforced NiCoCrTi0.5Nb0.5 HighEntropy Alloy Coating by Laser Cladding: Microstructure and Wear Behavior Ying Zhang1 • Tengfei Han1 • Meng Xiao2 • Yifu Shen1
Submitted: 23 November 2019 / in revised form: 10 June 2020 ASM International 2020
Abstract The diamond enhanced (NiCoCrTi0.5Nb0.5)Cx (x = 3, 6, 12 wt.%) high-entropy alloy coatings were wellprepared by laser cladding, which are denoted as C3, C6 and C12, respectively. The macroscopic morphology, phase, microstructure, hardness and wear resistance were investigated. The coatings without pores and cracks, are well-metallurgically bonded with the substrate. The width, melting depth and dilution rate of (NiCoCrTi0.5Nb0.5)Cx coating decrease with the increase of diamond content. The coatings are mainly composed of BCC solid solution, (Ti,Nb)C and Cr3C2. The increase of diamond content results in the precipitation of (Ti,Nb)C and Cr3C2, and the coating with x = 12 wt.% retains more diamonds. The hardness of coatings is much higher than that of the substrate. As the diamond content increases, the average hardness of (NiCoCrTi0.5Nb0.5)Cx coating increases first and then decreases. The abrasive wear occurs in each coating. The wear depth, roughness and wear rate decrease first and then increase as the diamond content increases. The C6 coating with the better wear resistance produces a smooth worn surface, which indicates that C6 coating can be fully applied to various tools, molds and mechanical parts. Keywords diamond high-entropy alloy laser cladding microhardness microstructure wear resistance
& Yifu Shen [email protected] 1
College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics (NUAA), Nanjing, People’s Republic of China
2
Nanjing Institute of Advanced Laser Technology, Nanjing, People’s Republic of China
Introduction Alloys in traditional sense contain a major element and possess other elements to improve their properties, such as steel, aluminum alloys and magnesium alloys (Ref 1-3). In recent years, Yeh et al. (Ref 4) broke through the traditional design concept of alloys and proposed a new alloy consisting of multiple major elements with equimolar or near-equimolar ratios, which is defined as high-entropy alloy (HEA). The HEA with at least 5 major elements (the concentration of each element is between 5 and 35 at.%) has the large mixing entropy (DSconfig C 1.61R, R is the universal gas constant). In particular, HEA consists of solid solutions with BCC and/or FCC structure, and their microstructure can reach nanoscale or even amorphous (Ref 5-7). HEAs possess good properties such as high hardness, excellent wear resistance, promising corrosion resistance, superb oxidation resistance, desirable hightemperature performance and ideal magnetic properties (Ref 8-11), which make them increasingly popular in many fields, such as tools, molds, dies and mechanical parts (Ref 12-14). Additionally, with the development of coating technologies, the application scope of
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