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Ni60 alloy is one of the important brands of nickel-based self-fusing alloys. It is widely used in industries such as metallurgy, mining, and other fields for the repair and protection of fragile parts. However, there is little literature on the effect of C content on its properties. In this study, two Ni60 alloy coatings with different C contents prepared by flame spraying and remelting were investigated by means of XRD, SEM, EBSD, friction wear testing, thermodynamic calculation, etc. The results showed that the calculated freezing range (FR) of Ni60 decreased from 983-1165.90 °C to 980-1154.28 °C and the melting range (MR) of Ni60 decreased from 966.27-1089.28 °C to 958.91-1045.41 °C when the C content increased from 0.72 wt.% (S1) to 1.01 wt.% (S2). Besides, the Cr7C3 phase size of the Ni60 layer increased with the increase of C addition. The coating shrinks during the remelting and solidification process, and the inner pores do not have sufficient time to escape, caused by the decreased FR, leading to the generation of holes and the degradation of surface quality in S2. However, the hardness of the S2 was 66 HV higher than that of S1, and the wear resistance of the S2 coating was superior as well because of more precipitated carbides therein. This work would give a hint at balancing the processability and mechanical properties for the development of high-performance coatings. [ABSTRACT FROM AUTHOR]

The industry widely uses WC coatings to protect vital machine parts, including industrial gas turbines, ball valves, and aircraft landing gear shafts. To enhance the comprehensive performance of WC-10Co cemented carbide coatings, this study added VC and Cr 3 C 2 grain inhibitors to refine the WC particles. Two novel powder compositions, S1 (WC-10Co-2Cr 3 C 2 -2VC) and S2 (WC-10Co-2VC-2Cr) were developed using the spray granulation method, alongside a commercial WC-10Co-4Cr powder as a control. These coatings were applied to 316 stainless steel substrates using the HVOF technique and subjected to XRD, SEM, hardness, friction, and electrochemical analysis. The microstructures, phase compositions, and various properties of WC-10Co-2Cr 3 C 2 -2VC and WC-10Co-2VC-2Cr coatings were systematically investigated. The results indicate a significant reduction in decarburization and porosity in S1 and S2 coatings compared to the commercial WC-10Co-4Cr coatings. VC and Cr 3 C 2 suppressed the Ostwald ripening phenomenon, leading to smaller WC particle sizes in S1 and S2 coatings. In terms of performance, WC-10Co-2Cr 3 C 2 -2VC exhibited the highest hardness and superior wear resistance, while the WC-10Co-2VC-2Cr coating displayed the lowest corrosion rate in a 5 wt% H 2 SO 4 solution at 25 °C, all while maintaining excellent mechanical properties. This study opens potential directions for the creation of high-performance WC-based coatings. • VC and Cr 3 C 2 suppressed the Ostwald ripening phenomenon, leading to smaller WC particle sizes. • WC-10Co-2Cr 3 C 2 -2VC exhibited the highest hardness and superior wear resistance. • WC-10Co-2VC-2Cr coating displayed the lowest corrosion rate in a 5 wt% H 2 SO 4 solution at 25 °C. [ABSTRACT FROM AUTHOR]

To optimize the toughness and hardness of laser surface‐hardened high‐carbon–chromium (52100) steel, the effect of preheating on microstructure evolution and impact property is studied, and the impact fracture mechanism is analyzed. The results indicate that preheating deepens the hardened depth, facilitating grain coarsening and cementite dissolution near the surface. Regardless of preheating, the size distribution of cementite follows a typical lognormal distribution. Laser surface hardening leads to a decrease in impact absorbed energy. Preheating at 160 °C increases the impact absorbed energy by ≈25%, at which point the maximum hardness is still as high as 860 HV0.3. The impact absorbed energy of spheroidized microstructure tends to be larger before laser hardening and reduces after laser hardening. The impact toughness is the combined result of the brittleness of the hardened layer, residual stress, and substrate microstructure. Under the impact load, microcracks nucleate near the surface of the hardened layer and propagate in the form of intergranular fracture and then propagate in the form of transgranular fracture toward the inside of the hardening layer and substrate. Herein, a novelty research work on optimizing the impact properties during laser hardening through preheating and adjusting initial microstructure is provided. [ABSTRACT FROM AUTHOR]