基于压痕蠕变试验的TA2蠕变特性及变形规律分析

Application of indentation creep test on creep characteristics and deformation rule analysis of TA2

随着TA2在化工、海洋、电力等领域中的广泛应用,合理评价其蠕变变形对于相关设备的安全稳定运行具有重要的意义。为了探究TA2蠕变行为,开展不同条件下的平头压痕蠕变试验研究,分析TA2压痕蠕变变形特性,并探究蠕变损伤对TA2变形规律的影响。结果表明:从20到300℃,TA2均出现显著的压痕蠕变变形。随着温度或载荷的升高,蠕变变形速率逐步增大,蠕变变形在整体变形中占比更大。在低载荷条件下,TA2蠕变变形并不显著,但是随着温度的上升,产生显著压痕蠕变变形所需载荷会逐步下降。幂律方程可以较好地描述TA2压痕蠕变变形的第一阶段,且系数a具有显著的蠕变相关性。随着蠕变载荷、温度的升高,系数a逐步上升;而相比于新材料,相同条件下的蠕变损伤材料蠕变变形更小,a更小。以此为基础,建立拟合参数与蠕变参数之间的关系。当蠕变变形较大时,压头下方的试样微观组织存在明显的区域性变化。在距离压头下方约0.15~0.50 mm处,材料硬度上升,晶粒显著变形并呈半球形分布;相似的,在上表面的接触边界区域也呈现硬度上升规律。

With the wide application of TA2 in chemical,marine,electric power and other fields,reasonable evaluation of its creep deformation was of great significance for the safe and stable operation of related equipment.To analyze the creep behavior of TA2,cylinder flat indentation creep test was conducted at different conditions.The creep deformation characteristic was analyzed.Meanwhile,the influence of creep damage on the material deformation was discussed.Results showed that indentation creep deformation could be found from 20 to 300℃.With the increase of temperature or load,the indentation creep depth rate increased and the creep deformation accounted for a larger proportion of the whole depth.It should be noted that creep phenomenon was not apparent when the load was relative low.However,with the increase of temperature,the minimum load that was needed to cause creep decreased.The power relation could be used to describe the primary creep stage of indentation creep deformation reasonably.A significant creep correlation was found for parameter a.The value of parameter a increased with the increase of creep load or temperature.Compared to new material,a lower value of parameter a was obtained for the damaged material at the same condition.Finally,the relation between coefficient and creep parameters was established.Apparent regional variation of material microstructure could be found at the area under the indenter when the indentation creep deformation was large.At the distance about 0.150.50 mm under the indenter,material hardness increased,and significant grain deformation with hemispherical distribution was presented.Similarly,the increase of hardness could also be found in the contact boundary of upper material surface.