基体表面粗糙度对HVOF粒子沉积行为的影响

Effect of Substrate Surface Roughness on Deposition Behavior of Particles by HVOF

目的研究超音速火焰喷涂时,45^(#)碳钢基体表面粗糙度对WC-12Co粒子在其表面的沉积变形行为的影响。方法基于Johnson-Cook塑性材料模型与Thermal Isotropy-Phase-Change热材料模型,采用LS-DYNA进行建模分析。结果不同45^(#)碳钢基体表面粗糙度下,WC-12Co粒子的沉积行为存在明显差异,波峰高度与波谷深度的差异造成粒子不同程度的不规则变形。当基体表面粗糙度Ra=10.26μm时,粒子沉积位置不同将引起粒子最终沉积形貌不同,但粒子的冲击均引起波峰偏移变形,且粒子不同程度地填充弥补波谷。粒子沉积过程中,粒子中下部与粒子先接触基体处的屈服应力、等效塑性应变与温升均高于粒子顶部以及粒子后接触基体处。Ra=0μm时,粒子等效塑性程度最大,等于2.03,此时粒子温度峰值最高为1562 K,粒子-基体结合界面局部区域屈服应力迅速下降为0,但基体变形程度较低,二者结合面积有限,粒子-基体结合强度较弱。Ra=5.34μm时,粒子的屈服应力在非理想平面状态下最为稳定,且等效塑性应变与温升幅度最大,分别为1.83以及1496 K。结论理想表面状态下,粒子屈服应力、等效塑性应变以及温度变化最佳,但粒子-基体结合面积较低,并不利于粒子沉积。非理想表面状态下,一定程度增加Ra,可促进粒子塑性变形,提升粒子温度,增大结合面积,降低粒子屈服应力,但粒子沉积形貌相比理想表面沉积形貌更加多样复杂。此外,过度增加Ra将引起波峰变形偏移,消耗大量粒子动能,粒子主要用于填充弥补波谷,等效塑性变形程度与温升幅度下降,屈服应力增加,不利于粒子沉积。

The effect of substrate surface roughness on the deposition deformation behavior of WC-12Co particles on 45^(#)carbon steel substrate under HVOF spray is studied.Based on Johnson-Cook plastic material model and Thermal-Isotropy-Phase-Change model,LS-DYNA is used for modeling analysis.The results show that there are obvious differences in the deposition behavior of WC-12Co particles on the 45^(#)carbon steel substrate under different substrate surface roughness,and the differences of peak height and trough depth lead to irregular deformation of particles in different degrees.When the substrate surface roughness Ra=10.26μm,the final morphology of particles will be different due to different deposition positions,but the impact of particles will cause the wave crest shift and deformation,and the particles will fill in different degrees to compensate for the wave trough.During the deposition process,the yield stress,equivalent plastic deformation and temperature rise of the middle and lower parts of the particles contacting the substrate first are higher than those at the top of the particles where the particles contact the substrate later.When Ra=0μm,the maximum equivalent plasticity of particles is 2.03,and the maximum temperature is 1562 K.The yield stress in the local region of the particle-substrate interface rapidly decreases to 0,but the deformation degree of the substrate is low.The bonding area of the two is limited,and the particle-substrate bonding strength is weak.When Ra=5.34μm,the yield stress of the particles is the most stable in the non-ideal plane state,and the equivalent plastic strain and temperature rise amplitude are 1.83 and 1496 K respectively.Therefore,it can be concluded that the yield stress,equivalent plastic strain and temperature change are the best under the ideal surface state,but the particle substrate bonding area is low,which is not conducive to particle deposition.Under the condition of non-ideal surface,increasing Ra to a certain extent can promote the plastic deformation of particles,increase the particle temperature,the bonding area and reduce the yield stress of particles,but the morphology of particles deposition is more diverse and complex than that of ideal surface deposition.In addition,the excessive increase of Ra will cause the peak deformation shift and consume a lot of particle kinetic energy.The particles are mainly used to fill the wave trough.The equivalent plastic deformation degree and temperature rise range decrease,and the yield stress increases,which is not conducive to particle deposition.