Cr12MoV cold work die steel is widely used in the roll industry due to its advantages, such as minimal deformation, high abrasion resistance, and large bearing capacity. Cr12MoV rolls have high hardness and brittleness and are prone to spalling, pitting, cracking, and other micro-area damage during service. The service conditions of rolls are harsh, as they are often subjected to significant impact, extrusion, and external friction. This makes them highly susceptible to localized damage, such as large-area spalling and cracking defects, ultimately leading to Cr12MoV roll failure. Laser repair is a method used to restore damaged rolls, producing a dense structure and metallurgical bonding at the interface. It has become an important technology for repairing Cr12MoV rolls. However, under conventional laser processing, the surface hardness of the repair layer fluctuates significantly, and the hardness variation in the interface transition zone is pronounced. This negatively affects the repair of cold rolling work rolls used in rolling high-precision plates, severely impacting both rolling accuracy and roll service life. This paper introduces the application of laser beam oscillation in welding to promote the transformation of columnar crystals into equiaxial crystals. This technique addresses issues such as poor surface hardness uniformity in repaired Cr12MoV rolls, large hardness fluctuations in the interface transition zone, and metallurgical defects. The findings provide a valuable reference for achieving high-quality surface repair of Cr12MoV rolls.

Laser cladding of Fe90 alloy powder is applied to the surface of Cr12MoV cold rolling work rolls to create additive layers. A subsequent layer is then deposited on both the conventional manufactured layer and the single manufactured layer. Initially, the forming quality of the additive layers under the two different surface conditions of the manufactured layers is compared. Next, the microstructural features of the cross-sections and longitudinal sections of the additive layers are examined using a metallographic microscope, followed by a comparative analysis of the microstructures at the same depths within the additive layers. X-ray diffraction is then used to analyze the phase compositions of the additive layers. Additionally, the energy dispersive spectrometer (EDS) line scanning is conducted to examine the distribution of the primary elements, Fe and Cr, in the repair layers. Finally, the hardness and wear resistance of the additive layers under different manufactured layer surface conditions are tested. By combining microstructural analysis, element distribution, and other evaluations, the impact mechanism of manufactured layer surface grinding on the uniformity of surface hardness in the additive layers is explored.

Before manufactured layer surface grinding, the additive layer surface is uneven, with an average surface roughness of 24.41 μm (Fig. 3). The microstructure of the cross-sectional and longitudinal sections of the additive layer consists of a mixture of columnar and equiaxed crystals. The surface hardness varies widely, reaching as low as 178.1 HV, with a hardness fluctuation coefficient of 45.7. Additionally, extensive delamination pits are observed under friction wear (Figs. 12 and 14). After manufactured layer surface grinding, the additive layer surface becomes flatter, with an average surface roughness reduced to 15.50 μm (Fig. 3). Furthermore, the manufactured layer enhances the consistency of laser energy absorption on its surface, improving the uniformity of the melt pool temperature and flow field. This stabilization of grain growth conditions transforms the microstructure into a uniform dendritic crystal form (Figs. 11 and 12). The range of surface hardness decreases to 97.5 HV, with the hardness fluctuation coefficient reduced to 23.9, significantly improving surface hardness uniformity. The friction coefficient decreases from 0.65 to 0.47, and both the width and depth of the wear tracks are significantly reduced (Figs. 12 and 13).

In this study, an Fe90 alloy additive layer is prepared on the surface of Cr12MoV cold rolling work rolls using laser cladding technology, and the effect of manufactured layer surface grinding on the additive layer is studied. Surface grinding of the manufacturing layer improves the forming quality of the additive layer, reduces surface roughness, decreases the temperature gradient between the center and edges of the melt pool, and increases the solidification rate. It also results in a more uniform distribution of Fe and Cr elements within the additive layer, enhances the consistency of the crystal growth environment, and promotes a transition to a uniform microstructure, thereby suppressing microstructural variations in the additive layer. Overall, this study demonstrates that incorporating a surface grinding process into the laser cladding procedure enhances the forming quality, hardness uniformity, and wear resistance of the additive layer.