Tengfei Han

Among many methods to enhance the crack resistance of laser cladding coatings, adjusting the composition of laser cladding material is the most simple, feasible, and effective method. To improve the plastic toughness and crack resistance of A100 laser cladding coating, Ni and Ti powders of an equal molar ratio were added to A100 powder as laser cladding powder. Laser cladding technology prepared A100-(Ni-Ti) coatings without crack defects. The cladding coatings’ phase composition and microstructure were analyzed using XRD and SEM, respectively. A ring-block friction and wear tester tested the wear resistance of the A100-(Ni-Ti) cladding coatings. A100-(Ni-Ti) cladding coatings mainly contain martensite and austenite. The elements Ni and Ti are distributed primarily in the austenitic phase region. The results show that adding Ni and Ti elements can reduce the microhardness of A100 cladding coatings. The average microhardness of the A100-0%(Ni-Ti) cladding coating is 532.50 HV, and the average microhardness of the A100-10%(Ni-Ti) cladding coating is 430.99 HV, while the average microhardness of the A100-30%(Ni-Ti) cladding coating is only 307.49 HV. The wear surface of the A100-10%(Ni-Ti) cladding mainly shows pits and a small amount of adhesive wear. The A100-20%(Ni-Ti) and A100-30%(Ni-Ti) cladding coatings show severe adhesive wear. The A100-10%(Ni-Ti) cladding with high microhardness and good run-in performance exhibits the best wear resistance.

To improve the hardness and wear resistance of mild steel, A-100 ultra-high-strength steel cladding coatings were prepared on the surface of mild steel by laser cladding. In this study, the effects of laser cladding process parameters on the forming quality, phase composition, microstructure, microhardness and wear resistance of the A-100 ultra-high-strength steel cladding coatings were researched. The results show that the main phase of the coating is martensite and a small amount of austenite. The microstructures of the upper part of the cladding coatings are mainly equiaxed grains, while those of the lower part are mainly columnar grains. With an increase in laser specific energy, the microstructures of the cladding coatings become coarse. When the laser specific energy is 70.8 J/mm², the microhardness of the cladding coating is the highest, and the maximum average microhardness of the cladding coatings is 548.3 HV. When the laser specific energy is low, the wear of the cladding coatings is mainly pitting, while when the laser specific energy is high, the wear type of the cladding coatings is mainly adhesive wear. Moreover, the microhardness and wear resistance of the cladding coatings are reduced if the laser specific energy is too high.

To enhance the microhardness and wear resistance of low-carbon steel, laser cladding was employed to create A100-Y₂O₃ cladding coatings that remained free of cracks. The phase composition, microstructure, and element distribution of these coatings were examined using XRD and SEM analyses, respectively. The microhardness and wear resistance of the A100-Y₂O₃ cladding coatings were tested by an HXS-1000 A type digital liquid crystal intelligent microhardness tester and an ML-10 friction and wear tester, respectively. The XRD results show that the addition of Y₂O₃ did not change the phase composition of the A100-Y₂O₃ cladding coatings. With the addition of Y₂O₃, the grains of the A100-Y₂O₃ cladding coatings are finer compared with those of the A100-0%Y₂O₃ cladding coating. The upper part of the A100-Y₂O₃ cladding coatings were composed of fine equiaxed grains. The average microhardness of the A100-0%Y₂O₃ cladding coatings was 532.489 HV. With the addition of Y₂O₃, the microhardness of the A100-Y₂O₃ cladding coatings was obviously improved, and the average microhardness of A100-1.5%Y₂O₃ coating reached 617.290 HV. The A100-Y₂O₃ cladding coatings were reduced, and the worn surface became relatively smooth owing to the addition of Y₂O₃. The addition of Y₂O₃ significantly improved the wear resistance of the A100-Y₂O₃ cladding coatings.

Laser cladding technology is a reliable and efficient surface modification technology, which has been widely used in surface alloying and composite processing of steel materials. Firstly, the characteristics of laser cladding technology were introduced, and the effects of process control and the material system on the geometric shape, size, microstructure, and properties of cladding coating were analyzed by summarizing the research results of laser cladding on steel surfaces. The results show that with the increase of laser power, the dilution rate and width of the cladding coating increase, and the grain becomes coarse. Thus, the wear resistance deteriorates. Compared with alloy cladding coating, composite cladding coating exhibits better wear and corrosion resistance, but the plastic toughness is worse than alloy cladding coating. The research progress of surface alloying and composite processing of steel worldwide was analyzed from various aspects. Current results suggest that laser cladding alloying and compounding can enhance the wear resistance and corrosion resistance of steel materials. Based on the summary of the current research results, the development prospect and planning of laser cladding technology in the field of surface alloying and composite processing of steel are further pointed out.