Research On The Hot Working Die Repaired By Laser Biomimetic Coupling Remelting And Alloying

The failure modes of hot work dies include erosion, abrasion, cracking, collapse andthermal fatigue. And as the predominant failure mode, the thermal fatigue has been limitingthe life of the hot work die. Due to the harsh service conditions, the surface of hot workdies would suffer from the stress generated from the thermal cycling process. When thetemperature increases, the surface would be subject to compressive stress and strain, whiletensile stress and strain would be generated with the temperature decreasing. Currently,there is a huge gap between our country and the foreign countries in the quality of the hotwork die, especially in the life of the hot work die.To improve the life of the hot work die, a biomimetic coupling thermal crack modelfor the surface of the hot work die has been proposed, by exploring the fatiguecrackretardation and arrest mechanisms in organisms. On the H13steel surface with theprefabricated hot cracks the fused biomimetic coupling units were prepared by laser surfacetechnology, with the aim to repair and strengthen the surface. And the thermal fatigueresistance between the samples with and without the prefabricated hot cracks has also beencompared. The role of the morphology and the amount of the fused biomimetic couplingunits on the thermal fatigue resistance of the bionic coupling sample has also been studiedand discussed in details. In order to improve the units’thermal fatigue resistance further, theunits were respectively alloyed with the powder of Co50and Fe30A by using lasertechnology. The effect of the strengthened units by alloying on the thermal fatigueresistance of the repaired the samples has been investigated.The results indicate that the fused biomimetic coupling units are composed of thehighly refined martensite and the retained austenite, and these units not only have a goodresistance to the nucleation of thermal fatigue cracks, but also can effectively retain thedevelopment of the cracks. In the formation of the strengthened units by laser alloying, boththe chemical composition and the microstructure of the material changed, which wasrelated to the physical and chemical reactions on the material surface. These alloyed unitsmaintained the refinement feature of the fused units, and their strengths were also improvedfurther. The alloyed units had a better thermal fatigue resistance than the fused units, andthe units alloyed with the Co50powder were best.