磷酸二氢钾晶体单点划痕试验研究

Experimental Study of Single-tip Scratching on Potassium Dihydrogen Phosphate Single Crystal

使用单颗粒划痕试验来研究磷酸二氢钾(Potassium dihydrogen phosphate,KDP)晶体摩擦磨损特性,同时采用高频记录仪对划痕过程中晶体的力学行为数据进行采集。利用光学显微镜和扫描电子显微镜观察划痕的表面形貌并分析其去除机理。比较不同划痕方向的摩擦因数μ,结果表明μ是随着划痕位移s的增加而增加。当s<3mm时,μ的增加比较平缓,此时晶体以塑性去除为主;当s>3mm时,μ发生剧烈的振荡,此时晶体以脆性去除为主。不同划痕方向产生的沟槽侧向裂纹密度随着法向加载的增大而变得密集,最后出现破碎和崩裂,但是侧向裂纹扩展方向与划痕方向所成角度有所差异,这是KDP晶体复杂的滑移系造成的。为了观测划痕产生的亚表面损伤,试验使用截面抛光法和择优腐蚀法,并测定损伤层深度。结果表明,沿[100]晶向的划痕损伤深度最大,且基本上无波动;对于沿[110]和[120]的亚表面划痕损伤深度有很大的波动现象,但在初始划痕阶段沿[120]的划痕损伤深度相对较小。

The friction and wear characteristics of potassium dihydrogen phosphate（KDP） single crystals are evaluated by single-tip scratch testing.The force profiles during the scratch process are captured by using high frequency force transducers.The mechanism of materials removal is characteristized by optical microscopy and scanning electron microscopy.It is concluded that the friction coefficients μ of different scratching directions increase with the increase of scratching displacements.When the scratching displacement s 3 mm,the friction coefficients μ increase smoothly and slowly,and the materials are mainly removed plastically.However,when the scratching displacement s3 mm,the friction coefficients μ oscillate strongly,and the materials are mainly removed brittlely.The lateral cracks of the scratch groove along different scratch directions become denser with the increase of scratch displacement,and even the phenomenon of brittle fractures and break-up appears in the sides and bottom of the groove.At the same time,it is observed that the angle between the growth direction of the lateral cracks and the scratching direction is different,due to the relatively complex slide system of KDP crystals.To observe and analyze the subsurface damage induced by the scratch,section-polishing method and preferential-etching method are used and the depth of the damage is measured as well.The results show that the damage depth along [100] is the deepest and basically without fluctuation,while the damage depths along [110] and [120] fluctuate greatly.However,the damage depth along [120] relatively small in the initial stage of scratching.