Nickel-based self-lubricating composite coatings (Ni60/Ag(Cu)/nanoNi/h-BN) with different amounts of Nb were manufactured by laser cladding on the surface of 42CrMo steel. The effects of carbide forming element Nb on the microstructure evolution and tribological properties of the composite coatings were investigated. The results show that Nb is easily precipitated at grain boundaries and reacts with carbon to form the in-situ synthesized phase NbC. The grains were refined and rich substructures appeared inside, which improved the strength and hardness of the coatings. The average microhardness of the coatings with 5.5 wt% Nb addition reaches 731.5HV, which is 192.1HV higher than that of NCA0(0 wt%), and 3.17 times that of the substrate. Compared to NCA0, the average friction coefficient and wear rate of NCA3 decreased by 38.1% and 30.6%, respectively. The solid lubricant formed a lubricant film during wear, and the fine grains facilitated oxidation wear, resulting in the formation of oxidation film. The lubricant film, oxidation film and the increase in hardness together improved the tribological properties of the coating.

中文翻译：

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Nb颗粒对激光熔覆Ni60/Ag(Cu)/nanoNi/h-BN复合涂层微观结构和摩擦学性能的影响


采用激光熔覆技术在42CrMo钢表面制备了不同Nb含量的镍基自润滑复合涂层（Ni60/Ag(Cu)/nanoNi/h-BN）。研究了碳化物形成元素Nb对复合涂层微观结构演变和摩擦学性能的影响。结果表明，Nb很容易在晶界析出，并与碳反应形成原位合成相NbC。晶粒细化，内部出现丰富的亚结构，提高了涂层的强度和硬度。添加5.5 wt% Nb的涂层平均显微硬度达到731.5HV，比NCA0(0 wt%)提高了192.1HV，是基体的3.17倍。与NCA0相比，NCA3的平均摩擦系数和磨损率分别降低了38.1%和30.6%。固体润滑剂在磨损过程中形成润滑膜，细小的晶粒有利于氧化磨损，导致氧化膜的形成。润滑膜、氧化膜和硬度的增加共同改善了涂层的摩擦学性能。