激光内送粉高速熔覆Cr50Ni合金稀释率及单道形貌分析

Analysis of Dilution Rate and Single Channel Morphology of High-speed Cladding Cr50Ni Alloy by Laser Inside-beam Powder Feeding Process

目的研究"光内送粉"正离焦高速熔覆Cr50Ni合金单道形貌及稀释率变化影响因素,制备耐磨、耐腐蚀绿色无污染的金属表面涂层,从而替代传统电镀。方法采用"光内送粉"正离焦新型耦合技术开展高速熔覆工艺试验,即在304不锈钢基体上制备Cr50Ni合金熔覆层。建立了光内送粉条件下粉末遮光模型,得出了送粉速率与粉末遮光率的关系,从而得到最终照射在基体上的激光能量,而激光能量密度与稀释率呈正相关,以此分析了不同送粉速率对熔覆层稀释率的影响,同时考察了不同离焦量对熔覆层稀释率以及单道熔覆厚度的影响,分析了最佳熔覆层的显微组织成分变化和硬度变化趋势。结果当扫描速度为9 m/min、离焦量为+1^+2 mm、激光功率为1.85 kW时,可获得厚度约为121~452μm、稀释率为12.9%~75%、硬度值为280~320HV的表面形貌较好的熔覆层。粉末粒子直径为50μm时,在16~32g/min送粉速率下,粉末遮光率为16.6%~33.1%。熔覆层底部的晶粒形态主要为明显的柱状枝晶,由于冷却速度快,进入熔池中的气体来不及逃逸,使得熔覆层内部存在一些微小气孔。结论 "光内送粉"正离焦光粉耦合新技术采用Cr50Ni合金材料,在激光功率为1.85 kW、送粉速率为28 g/min、离焦量为+2 mm、扫描速度为9 m/min的工艺参数下,可以获得理想的单道成形效果,实现高速熔覆。

The work aims to study the influence factors on the changes of the Cr50Ni alloy single-channel morphology bypositive defocusing high-speed cladding of"laser inside-beam powder feeding"and the dilution rate,to prepare a wear-resistant and corrosion-resistant green non-polluting metal surface coating to replace the traditional plating.The high-speed cladding process test was carried out with the"laser inside-beam powder feeding"coupling technology.A Cr50Ni alloy cladding layer was prepared on a 304 stainless steel substrate.A model of powder shading under the condition of laser inside-beam powder feeding was established,and the relationship between the powder feeding rate and the powder shading rate was obtained,so that the laser energy finally irradiated on the substrate was obtained.The laser energy density was positively correlated with the dilution rate and the effect of different powder feeding rates on the dilution rate of the cladding layer was analyzed.At the same time,the effects of different defocusing amounts on the cladding layer dilution rate and the thickness of a single cladding layer were investigated.The microstructure composition change and hardness change trend of the best cladding layer were analyzed.When the scanning speed was 9 m/min,the defocusing amount was+1^+2 mm,and the laser power was 1.85 kW,the cladding layer with better surface morphology,a thickness of about 121~452μm,a dilution rate of 75%~12.9%,and a hardness value of 280~320HV could be obtained.When the powder particle diameter was 50μm,the powder shading rate was 16.6%~33.1%at a powder feeding rate of 16 g/min to 32 g/min.The grain morphology at the bottom of the cladding layer was mainly obvious columnar dendrites,and there were some tiny pores inside the cladding layer due to the inability of the gas entering the molten pool to escape quickly.The new technology of"laser inside-beam powder feeding"defocusing powder coupling is based on Cr50Ni alloy material.Under the laser power of 1.85 kW,the powder feeding rate of 28 g/min,the defocus amount of+2 mm,and the scanning speed of 9 m/min,the ideal single-pass forming effect can be obtained to achieve high-speed cladding.