前混合水射流速度对18CrNiMo7–6渗碳钢表面粗糙度及残余应力的影响研究

Effect of Pre-Mixed Water Jet Velocity on Surface Roughness and Residual Stress of 18CrNiMo7–6 Carburized Steel

在专用前混合水射流装备平台上,通过改变压力控制射流速度,从表面粗糙度与残余应力两方面评价不同射流速度对18CrNiMo7–6渗碳钢的表层改性效果。在对水、丸粒冲击作用过程分析的基础上,建立射流速度与冲击应力的关系,以喷嘴入口压力表示射流速度,采用单因素试验的方法进行研究。结果表明,在≤35MPa压力范围内,丸粒的冲击是试样表面产生塑性变形的主要原因。随着丸粒速度的提高,试样表面粗糙度增大,残余应力值以及层深不断增加。当丸粒速度超过178m/s后,表面粗糙度增幅较大,但残余应力提升不明显。综合表面质量与残余应力因素,前混合水射流中丸粒速度在143~178m/s范围内表层改性效果较优。

In this study,the jet velocity is controlled by changing the jet pressure on a new designed pre-mixed water jet modification system.The surface strengthening effect at different jet velocities on 18CrNiMo7–6 carburized steel is evaluated from two aspects of surface roughness and residual stress.Based on the impact stress analysis of water and shot in jet,the relationship between jet velocity and impact stress is established.With the jet velocity represented by the nozzle inlet pressure,experiments were carried out by using a single factor method.At the pressure below 35MPa,the impact of shot is the main reason for the plastic deformation of sample surface.The surface roughness and residual stress,as well as the layer depth of residual stress field,increase with the shot velocity.However,as the jet velocity exceeds 178m/s,the increase of surface roughness is obvious while the residual stress does not increases significantly.It is indicated that a good modification can be achieved in the pre-mixed water jetting with the particle velocity of 143–178m/s.