冷喷涂试件疲劳裂纹扩展规律试验研究

Experimental study on the fatigue crack growth law of cold sprayed specimens

冷喷涂作为一种新兴的表面处理技术,广泛应用于增材制造和零部件修复等领域。为了探究冷喷涂处理后Q355钢基体的疲劳裂纹扩展规律,对2组标准单边缺口3点弯曲试样进行了冷喷涂处理。在光滑的Q355B钢基材表面分别沉积了纯Al和A5052铝合金涂层,然后对冷喷涂试件和一组未喷涂光滑试件进行了3点弯曲疲劳试验,得到了裂纹尖端张开位移和裂纹长度、裂纹扩展速率和荷载循环次数的规律曲线并进行了对比分析。结果表明:在裂纹扩展长度相同的情况下,冷喷涂试件和未喷涂试件的裂纹尖端张开位移基本相同,且随着疲劳裂纹的延伸,裂纹尖端张开位移也随之快速增大;在一定的裂纹尖端张开位移范围内,冷喷涂处理可以降低疲劳裂纹扩展速率;采用裂纹尖端张开位移作为疲劳裂纹扩展控制参数对冷喷涂试件的疲劳裂纹扩展规律进行判定是准确的,且裂纹尖端张开位移通过试验容易获得,简单方便,可以同时满足裂纹尖端弹性和塑性的情况。

As a new surface treatment technology,cold spraying is widely used in additive manufacturing and parts repair.To investigate the fatigue crack propagation law of the cold-sprayed Q355 B steel substrate,two groups of standard single notched 3-point bending specimens were processed by cold spraying that pure Al and A5052 aluminum alloy coatings were deposited on the smooth Q355 B steel substrate surface,respectively.Then a fatigue test was performed on the cold sprayed specimens and a group of unsprayed polished specimens to obtain and compare the relation curves between the crack tip opening displacement and crack length,the crack propagation rate and load cycles.The results show that the crack tip opening displacements of cold-sprayed specimens and unsprayed specimens are close when the crack growth length is the same,and the crack tip opening displacement increases rapidly with the gradual fatigue crack growth.In a certain range of crack tip opening displacement,cold spraying can reduce the fatigue crack growth rate.It is accurate and reasonable to use the crack tip opening displacement as a fatigue crack growth control parameter to judge the fatigue crack growth law of cold sprayed specimens,and the crack tip opening displacement is easily obtained through test and can meet the condition of both the crack tip elasticity and plasticity.