Investigation On Microstructure And Properties Of Cu/TiB₂ Composite Coating On The H13 Hot Work Die Steel Surface Prepared By Laser Cladding

In this dissertation,Cu/TiB2 composite coatings were prepared on the surface of H13 hot work die steel by laser cladding method,and the surface properties of H13 steel were improved as well as friction and wear properties at high temperature.The effect of laser process parameters,TiB2 content on the microstructure and properties of the coating were studied through systematic experiments and the microstructure and property of the two coatings were compared with those of in situ TiB2 particles and TiB2 strengthened particles.The main results were as follows:The effects of process parameters and TiB2 addition on the microstructure and properties of the coating were studied by orthogonal experiment.The optimum addition amount of TiB2 was 30%wt as the optimized preparation parameters were laser power 995W,laser scanning speed was atlOmm/s,laser defocus was 35mm.The coating thickness was about 600?700?m,the hardness of the coating was about 550?650HV0.5,and decreased gradually along the depth direction.The hardness of the HAZ initially increased and decreased later to reach a matrix hardness rapidly,and the highest hardness achieved was 672HV0.5.The friction and wear properties of laser cladding coatings were evaluated by high temperature friction and wear test and thermal shock test.The experimental results showed that the cladded layer could significantly improve the high temperature friction and wear resistance of H13 steel surface.The coating was subjected to 100 thermal shocks without cracking and spalling.Laser cladding could be used for in-situ synthesis of TiB2 particles to enhance Cu based composite coatings as TiB2 particles synthesized in situ were dispersed in the coating.The hardness of the coating increased with the increase of(Ti+B)content,and the highest hardness reached 600HV0.5.The friction and wear properties of the coatings improved obviously with the increased of(Ti+B)content at high temperature,and the coating remained good after 100 times of thermal shock,and no exfoliation phenomenon was found.The microstructure and properties of the coatings obtained by the two preparation methods were compared.The results revealed that the direct addition of TiB2 reinforced granular coatings had higher hardness and better friction and wear resistance at high temperature.The in situ TiB2 particle coating had more uniform microstructure and better thermal shock resistance.