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激光快速成形技术是在激光熔覆技术及快速原型技术的基础上发展起来的一项新的先进的制造技术,能够实现高性能致密金属零件的快速无模近终形制造。但是,如果成形条件控制不当,易于在成形件中产生裂纹、气孔、夹杂、层间结合不良等缺陷,而裂纹是成形过程中最常见、破坏性最大的一种缺陷。本文采用微观测试分析方法,深入研究了激光快速成形某些合金粉末过程中熔覆层的开裂行为及裂纹形成机理。研究结果表明,对于镍基自熔合金,熔覆层的开裂属于冷裂纹范畴,是熔覆合金的低延性及成形过程中热应力双重作用的结果。对于奥氏体不锈钢等材料,熔覆层的开裂属于热裂纹范畴,裂纹产生的主要原因是由于凝固温度区间内晶界处的残余液相受熔覆层中的热应力作用所导致的液膜分离的结果。
Laser rapid prototyping technology is a new advanced manufacturing technology developed on the basis of laser cladding technology and rapid prototyping technology, which can realize the rapid dieless near net-shape manufacturing of high-performance dense metal parts. However, if the forming conditions are not properly controlled, defects such as cracks, pores, inclusions and poor interlayer bonding tend to occur in the formed part, and the crack is the most common and destructive defect in the forming process. In this paper, the cracking behavior and crack formation mechanism of the cladding layer during laser rapid prototyping of some alloy powders are investigated in detail by means of microscopic test and analysis. The results show that for the nickel-based self-fluxing alloy, the cracking of the cladding layer belongs to the category of cold cracking, which is the result of the dual ductile effect of the low ductility of the cladding alloy and the thermal stress in the forming process. For austenitic stainless steel and other materials, the cracking of the cladding layer belongs to the category of thermal cracking. The main reason for the crack generation is that the residual liquid phase at the grain boundary in the solidification temperature range is affected by the thermal stress in the cladding layer The result of separation.