Microstructure and Properties of Nickel-Based Gradient Coatings Prepared Using Cold Spraying Combined with Laser Cladding Methods

Abstract

A cold spray–laser cladding composite gradient coating (CLGC) was successfully formed on a Cu substrate. In comparison with traditional laser cladding gradient coatings (LGC), cold spraying the pre-set Ni-Cu alloy’s intermediate transition layer not only mitigates the negative impacts due to the high reflectivity of the copper substrate but also helps to minimize the difference in the coefficients of thermal expansion (CTE) between the substrate and coating. This reduces the overall crack sensitivity and improves the cladding quality of the coating. Besides this, the uniform distribution of hard phases in CLGC, such as Ni11Si12 and Mo5Si3, greatly increases its microhardness compared to the Cu substrate, thus resulting in the value of 478.8 HV0.5 being approximately 8 times that of the Cu substrate. The friction coefficient of CLGC is lowered compared to both the Cu substrate and LGC with respective values of 0.28, 0.54, and 0.43, and its wear rate is only one-third of the Cu substrate’s. These results suggest CLGC has excellent anti-wear properties. In addition, the wear mechanism was determined from the microscopic morphology and element distribution and was found to be oxidative and abrasive. This approach combines cold spraying and laser cladding to form a nickel-based gradient coating on a Cu substrate without cracks, holes, or other faults, thus improving the wear resistance of the Cu substrate and improving its usability.

Crack Formation Mechanisms and Control Methods of Laser Cladding Coatings: A Review

“…Consequently, the grain growth time is prolonged, resulting in coarser grains, as well as the formation of pores or impurities. The hot cracks in HSLA powder samples (the laser power is 2900 W and the scan speed is 10 mm/s) [25]; (b) the cold cracks in Ni-Cu alloy sample (the laser power is 5000 W and the scan speed is 30 mm/s) [35]; (c) cladding layer crack in ZhS32 alloy (the laser power is 600 W and the scan speed is 9 mm/s) [36]; (d) interface substrate crack in nickel-based K477A (the laser power is 576 W and the scan speed is 4 mm/s) [37]; (e) overlap zone crack in Ni60 (the laser power is 3200 W and the scan speed is 416.7 mm/s) [38].…”

“…Different types of crack morphology. (a)The hot cracks in HSLA powder samples (the laser power is 2900 W and the scan speed is 10 mm/s)[25]; (b) the cold cracks in Ni-Cu alloy sample (the laser power is 5000 W and the scan speed is 30 mm/s)[35]; (c) cladding layer crack in ZhS32 alloy (the laser power is 600 W and the scan speed is 9 mm/s)[36]; (d) interface substrate crack in nickel-based K477A (the laser power is 576 W and the scan speed is 4 mm/s)[37]; (e) overlap zone crack in Ni60 (the laser power is 3200 W and the scan speed is 416.7 mm/s)[38].…”