**2. Materials and Methods**

The substrates were made of AISI 1045 steel with dimensions of 40 mm × 20 mm × 5 mm. The cladding powders, mix-up of Ni35A and TiC, were supplied with grain sizes of 48–106 μm. The microscopic profiles and chemical components are illustrated in Figure 1 and Table 1, respectively.


**Table 1.** Chemical components of Ni35A and TiC particle (wt.%).

**Figure 1.** SEM image of cladding powder. (**a**) Ni35A; (**b**) TiC.

The laser cladding system used in work, as depicted in Figure 2, was comprised of an IPG laser generator YLS-3000 (Burbach, Germany), the wavelength is 1064 nm, continuous mode, a Lasermesh FDH0273 laser head (Novi, MI, USA) with a focal length of 300 mm, a FANUCM-710iC/50 industrial robot (Yamanashi, Japan), a TongfeiTFLW-4000WDR-01-3385 laser chiller (Sanhe, China), a Songxing CR-PGF-D-2 coaxial powder feeding machine (Fuzhou, China), a MitsubishiPLC controller, and SX14-012PLUSE laser pulse control system (Burbach, Germany). The laser was focused on the substrate with a spot diameter of 4 mm, and the cladding powder was supplied by the shielding gas argon at a pressure of 0.5 MPa.

**Figure 2.** Laser cladding system. (**a**) Experimental setup; (**b**) Schematic diagram.

Before cladding, the substrate was cleaned with acetone to remove surface impurities. The cladding powder was mixed up, according to the designated fraction, in a MITR-YXQM-2L planetary ball mill machine (MITR, Changsha, China) at a speed of 300 r/min for 30 min, followed by 30 min vacuum drying at a temperature of 120 ◦C. After laser cladding, the specimen was sectioned by wire-EDM (Electrical Discharge Machining), mounted, ground, polished, and etched in 4% nitric acid alcohol for 30 s. A series of observations was carried out, including microhardness test using MVA-402TS tester (HDNS, Shanghai, China) at a load of 500 gf and holding time of 30 s, macrographic measurement by a KH-1300 3D digital microscopy system (Hirox, Shanghai, China), metallurgical structure detection via a Hitachi TM3030 Plus scanning electron microscope (Hitachi, Tokyo, Japan), element quantification by A550I EDS (Austin, TX, USA), phase content analysis using XRD (Ultima IV, Rigaku Corporation, Tokyo, Japan) at a scanning speed of 4◦/min and scanning angles range from 20◦ to 80◦. The top surface of claddings was wear-tested using a Bruker UMT-2 universal tester (Bruker, Billerica, MA, USA) at conditions illustrated in Table 2, and the wear volume was calculated after the observation of scratch profiles. The wear rate was computed using Equation (1) after obtaining the wear volume from scratch profiles:

$$r = \frac{\Delta V}{F \times d} \tag{1}$$

where Δ *V* is the wear volume of cladding, *F* is the applied load during the wear test, and *d* is the sliding distance.


**Table 2.** Friction and wear parameter table.

Experimental runs were arranged according to the full factorial method using Design-expert 10.0. The experiment investigated the influences of four factors, including laser power, scanning speed, gas-powder flow rate, and particle ratio of TiC on the wear rate and microstructure evolution along the depth direction. The microstructure profile and element distribution in the cladding layer were also observed to reveal the correlation with macroscopic properties. The input variables and their levels are illustrated in Table 3. The experimental design matrix and observations are depicted in Table 4.

**Table 3.** Studied process variables and levels.



