热锻模梯度结构覆层的制备与环境服役行为

Hot forging die is easily to occur thermal expansion and thermal softening because of bearing periodical thermal fluctuation, which make wear and plastic deformation on die impression and the service life short. The existing homogeneous hot forging die steel and strengthening technique an not completely meet the performance requirement of the die impression temperature fluctuation zone. On this situation, using powder welding technology on hot forging die temperature fluctuation zone to form metal ceramic gradient structure layer, can solve the problem of requiring which near surface of hot forging die have high hardness and toughness under high temperature at the same time. In this study, the gradient structure hot forging die will be used to release thermal stress. Methods of the combination of experiments, FEM simulation and theory were described and the structure, characterization and thermal-mechanical properties of the gradient structure hot forging die have been studied. Furthermore, the configuration process and design method of the hot forging die were built and the relationship were revealed between welding layer structure, interfaces development and mechanical properties in the process of plasma powder welding technology. The thermal-mechanical properties and failure modes during forging process and the optimal selection of component, characterization, property characterization and evaluation were obtained. The above research can provide technical and science basis for developing gradient structure hot forging die under complicated thermal load working condition and expand to hot working die such as warm forging, isothermal forging，die-casting and will have a broad application prospect.

热锻模承受周期性急冷急热所引起的热胀冷缩及高温软化，导致模膛表面产生磨损、塑性变形等失效，使用寿命低。已有均质模具钢与强化技术均不能完全满足模膛温度波动区的性能要求。应用粉末喷焊技术在热锻模温度波动区制备出金属陶瓷梯度结构层，可解决热锻模模膛近表层要求高温强硬性和韧性兼备的问题。本研究以缓解热应力的热锻模梯度结构覆层为研究对象，以实验、有限元模拟与理论分析相结合的研究方法，对热锻模梯度结构覆层的构型、性能表征与热机械行为进行研究，建立热锻模梯度结构覆层的构型流程与设计方法，揭示等离子粉末喷焊工艺制造梯度结构过程中焊层组织、界面及与力学性能的演化关系，阐明热锻服役条件下的热锻模梯度结构覆层的热机械行为与失效模式，获得热锻模梯度结构覆层的结构、组分优选、性能表征与评价等关键技术，为开发复杂热机械载荷条件下梯度结构热锻模提供技术原型和科学基础。同时可扩展到温锻、等温锻造、压铸等热作模具。

采用等离子粉末喷焊技术制造热锻模梯度结构覆层，可解决热锻模模膛近表层要求高温强硬性和韧性兼备的问题，实现材料制备与模具制造的一体化。本研究以缓解热应力的热锻模梯度结构覆层为研究对象，从热锻模等离子喷焊覆层的制备工艺与显微结构、梯度结构覆层的性能表征与评价、热锻模覆层的高温损伤与服役性能、热锻模梯度结构覆层的循环载荷与设计方法等方面对热锻模梯度结构覆层进行了研究，获得了热锻模梯度结构覆层的设计方法、制造工艺、性能表征以及热锻服役特性，从而为新型异质结构热锻模制造提供技术科学基础，同时促进热锻模修复与再制造技术的发展。该研究可扩展到热冲压、热挤压与压铸等热作模具的制造与延寿领域。