Research on Surface Modification System by Using a Cavitating Jet

1.研制了考虑喷嘴直径尺度效应的表面改性系统。喷嘴直径从0.4mm到1.9mm。用PVDF换能器测量了不同空化条件下的空化影响。随着喷嘴直径的增大，空化冲击频率增加，空化冲击强度增大。降低试验水中的空气含量也增加了空化影响。通过测量硬度或残余应力来确定最佳强化时间或最佳扫描速度。空化射流可在材料表面引入残余压应力。压缩值在一定的处理时间或速度下达到饱和状态。在利用空化射流提高耐蚀性的情况下，根据电化学法电位与处理时间的关系，得到了最佳处理时间。针对空化射流的试验液，根据铁的Pourbaix图，明确了几种随ph值变化的试验液。对带缺口的齿轮和试样进行了强化。结果表明，与喷丸强化相比，空化喷丸强化表面非常光滑。空化射流还能将残余压应力引入刀具合金SKD61.6等硬质材料中。为了验证空化射流对疲劳强度的提高，进行了旋转弯曲疲劳试验。结果表明，空化射流可以提高合金的疲劳强度。通过电化学方法发现，空化射流可使材料的耐蚀性提高30%左右。

1.Surface modification system has been developed considering scale effects of nozzle diameter. Diameter of nozzle is from 0.4mm to 1.9mm.2.Cavitation impacts were measured by a PVDF transducer for various cavitating conditions. When the nozzle diameter was increased, the frequencies of the cavitation impacts were not only increased but also the intensity of the cavitation impacts increased. Reducing air contents ration in the test water also increased the cavitation impacts.3.Optimum peening time or optimum scanning speed was demonstrated by measuring hardness or residual stress. The cavitating jet can introduced compressive residual stress in the surface of the materials. The value of the compression was saturated at certain processing time or speed. In case of the improvement of the corrosion resistance by using a cavitating jet, optimum processing time was obtained by the relation between the potential by means of an electrochemical method and the processing time.4.Regarding test liquid of the cavitating jet, several liquids ware tested changing with pH.Suitable test liquids for iron were clarified referring Pourbaix diagram of iron.5.Peening for gears and specimens with a notch was carried out. It was revealed that the peened surface by a cavitating jet was very smooth comparing with that of the shot peening. The cavitating jet can also introduce the compressive residual stress into hard materials such as tool alloy SKD61.6.In order to demonstrate improvement of fatigue strength by suing a cavitating jet, a rotating bending fatigue test was carried out. It was shown that the cavitating jet could improve the fatigue strength. It was also revealed that the cavitating jet could improve the corrosion resistance about 30% by means of an electrochemical method.