Effect Of Scanning Speed On Microstructure Properties Of Ni-based Coatings

Laser cladding technology is an advanced material surface modification technology, which is controlled by a robot arm laser along a set trajectory to melt powder to prepare a strengthened coating, protect the substrate and extend the service life, and increase its scope of application. Laser cladding technology can meet more needs by changing the powder element ratio used in cladding.

Amorphous alloy is a kind of metastable material, which has both metal characteristics and glass structure. Because of its special atomic structure, there is no defect of crystal alloy, and it has excellent mechanical and physical properties. The Ni-based alloy material has good toughness, good oxidation resistance, high hardness, excellent high-temperature resistance, but the cost is high, by adding a certain proportion of cheap Fe-based powder, it can achieve better performance while reducing the cost. Different process parameters will significantly affect the amorphous state, and it is difficult to prepare completely amorphous cladding layer. By changing the process parameters and adding WC, the preparation of Ni-based coating has better wear resistance, and the friction coefficient is only 0.26.

Select Q235 as the base material, and its size is 300mm× 100mm ×10mm. The powder is selected as Ni-based amorphous powder, and the composition is shown in Table 1. The substrate is polished with a hand-held grinder and cleaned with ethanol.

                                                                                 Table 1 Chemical compositionofNi-basedpowder

Using IPG-4000W fiber laser, according to previous experience, the laser power is set to 2700 W, the powder feeding rate is 1.4r/min, the lap is 2mm, and the shielding gas argon flow rate is 15L/min. The coatings were prepared at laser scanning speeds of 6, 8, 10, 12 and 14mm/ s.

XRD, that is, X-ray diffraction (XD-3), was used to observe the phase changes of the coating layer. Friction samples with a hardness of 10×10 mm2 and friction samples with a diameter of 25mm were cut out by wire-cutting, as shown in Figure 1. Using the HV1000Z Vickers hardness tester, the load is 200 g, the time is 10s, and the test is conducted from the coating to the substrate every 0.25 mm along the cross section, and the distance from each point to the coating surface is recorded. After polishing with sandpaper and etching with 4% (volume fraction) nitrate alcohol, metallography was observed using 4XC type.

The friction test machine (CHMT23) was used to rub the coated ball and disc with GCr15 small ball, the speed was 500r/min, the load was 20N, and the time was 20 min. A 0.1mg precision electronic balance (FA2004B) was used to measure the quality of the samples before and after wear, and the test was repeated three times to obtain the average value.

1. The main phases of the coatings prepared at different scanning speeds are Fe and [FeNi], and there is no specific amorphous steamed bun peak. The microstructure of the coating is mainly composed of cellular crystals and columnar crystals, and the grains are compact and fine.

2. The thickness of the coating decreases with the increase of the scanning speed, and the thickness of the 8mm/ s coating is about 2 mm. The uniformity of the coating is the best at a scanning speed of 10 mm/ s, and the average hardness is left to right at 430 HV. The wear resistance of the coating can be enhanced first with the increase of the scanning speed, reaching the maximum value at the scanning speed of 10mm/ s, and then the wear resistance is inversely proportional to the scanning speed.

Xi'an Guosheng Laser Technology Co., Ltd. is a high-tech enterprise specializing in R&D, manufacturing and sales of automatic laser cladding machine, high-speed laser cladding machine, laser quenching machine, laser welding machine and laser 3D printing equipment. Our products are cost-effective and sold domestically and abroad. If you're interested in our products, please contact us at bob@gshenglaser.com.