表面形貌控制是超超临界发电机组用大规格镍基合金管材精确挤压成形时的关键问题。本课题拟通过改造热模拟试验机进行热挤压实验，利用AFM、SEM、EPMA、EBSD等检测方法，研究挤压时不同润滑状态和模具形貌对GH3625合金管材的内外表面形貌、表面成分和表面微观结构的影响规律。进而基于晶体塑性理论，构建包含润滑效果和模具表面形貌的镍管挤压过程表面形貌三维数值模拟模型，研究初始粗糙度、初始晶粒尺寸、织构、取向和模具表面状态与挤压后内外表面粗糙度的响应关系。最终根据摩擦学和材料表面工程的相关理论，推导镍管表面形貌与润滑状态、模具表面状态、工艺参数之间的数学模型，并结合数值模拟，得到控制镍管精确挤压成形时表面宏微观形貌的方法体系。

Surface morphology control is the key problem of precise extrusion of large diameter nickel base alloy pipe on ultra supercritical(USC) generating set. In this study，the effect of different lubrication conditions and mould morphology on internal and external surface morphology , surface composition and surface microstructure of GH3625 alloy tubing are analyzed through hot extrusion experiment on improved thermal simulated test machine coupled with detection method like AFM, SEM，EPMA and EBSD，etc. Then based on crystal plasticity model, mesoscopic 3-d numerical simulation model , which contained lubrication effect and the mold surface topography, are constructed to study corresponding correlations between initial roughness, initial grain size, texture, orientation ,mold surface state and the inner and outer surface roughness after extrusion. Finally, according to the relevant theories of tribology and surface engineering, the mathematical model between nickel pipe surface topography, lubrication state, mould surface state and process parameters is derived, and combined with numerical simulation, and ultimately getting method system of controling surface morphology and microstructure of nickel pipe during precise extrusion.