Effect of laser cladding Ti/B4C/dr40-based composite coatings for the surface strengthening of shaft part

•The Ti/B4C/dr40 composites by laser cladding can be employed to strengthen shaft part.•The content of Ti and B4C dominates the microstructure and performance of composites.•The Si and Mn elements homogenize TiC and TiB2 paticles in the composites.•The wear resistance of the shaft is improved due to in situ synthesis of TiC and TiB2. In-situ synthesized TiB2 and TiC particles reinforced dr40-based composite coatings are fabricated on shaft parts via laser cladding. The effects of the various contents of Ti and B4C in dr40 coating on the phase component, microstructure, and mechanical properties of the composite coatings are investigated. The Ti/B4C/dr40 composite coating primarily contains the evenly distributed phases of γ-Ni, CrB, TiC, TiB2, CrCX, NiTi, and [Fe, Ni] solid solutions. Precipitated hard phases weak the temperature gradient during the solidification process, and play a key role in dendritic cell refinement and increment of matrix supporting capacity. After evaluating the performance of the samples with different Ti and B4C contents, the 10% Ti/10% B4C/80% dr40 composite coating shows the highest microhardness of 632.66 HV0.3, which is about 1.4 times and 2.5 times higher than dr40 coating and 45# substrate, respectively. This composite coating has a clean wear surface with shallower and more uniform scratches. Besides, wear morphology is closely related to the size and distribution of strengthening phases and property of the matrix. As the 10% Ti/10% B4C/80% dr40 composite coating reveals high metallurgical bonding quality with the substrate, it is subsequently selected for strengthening material. The post-treated shaft part is evaluated in terms of its surface wear resistance and interface. The wear resistance reduces 50% of the strengthening shaft surface, and the machining quality meets the requirements. Thus, the strengthening process using laser cladding provides a basis for the application of Ti/B4C/dr40 composite coating for shaft part surface strengthening.