划痕法结合强度临界载荷值的影响因素分析

目的研究划痕法测试参数对临界失效载荷的影响,以便更准确地测定硬质薄膜的结合强度。方法采用磁控溅射技术在304不锈钢和Si片上制备氮化钛(Ti N)薄膜。采用扫描电镜观察薄膜的截面形貌和厚度,采用纳米压入法测试薄膜的硬度,采用划痕法测试薄膜的结合强度,研究不同划痕长度、划动速率和加载速率对临界载荷的影响。结果所制备Ti N薄膜致密,厚度约2μm,纳米压入硬度约2300HV,Ti N/304不锈钢体系为硬膜软基体。相同加载载荷(10 N)和划动行程(3 mm)条件下,增加划动速率(1~3 mm/min),导致首次声发射信号延迟;相同加载载荷(10 N)和划动速率(3 mm/min)条件下,随着划动行程的增加(3~9 mm),第三、四类失效模式逐渐减弱。结论采用划痕法测定结合强度时,应该以划痕形貌同时出现第一到第四模式时判断失效,并且对应典型声发射信号为参考;合理的测试参数范围,可重复出现临界载荷值。制备的Ti N薄膜声发射信号存在共同的临界特征值4.9 N,结合划痕形貌特征,判定其结合强度值为4.9 N。

Analysis of Influencing Factors on Critical Load of Adhesion Strength in Scratch Test

Objective In order to determine precise adhesion strength of hard film, the effects of parameters of scratch test on the critical failure load were studied and discussed. Methods Titanium Nitride ( TiN) film was deposited on 304 stainless steel plates and Si wafer by magnetron sputtering. The cross-section morphology and thickness of TiN film were observed by Scanning E-lectric Microscopy ( SEM) , the hardness was evaluated by nano-indentation method, the adhesion strength was studied by scratch tester, and the influences of slide length, slide speed and loading rate on the critical load were analyzed. Results As-deposited TiN film possessed dense morphology with a thickness of about 2 μm. The hardness of TiN film was about 2300HV and the TiN/304 stainless steel system was hard film and soft substrate. The increase of slide speed (1~3 mm/min) resulted in the first acoustic e-mission (AE) signal delay under the same load (10 N) and slide length (3 mm) conditions, the increase of slide length (3~9 mm) resulted in the gradual weakening of III and IV failure mode under the same load (10 N) and slide speed(3 mm/min) condi-tions. Conclusion In order to evaluate ideal adhesion strength, I to IV failure mode appearance should be observed in single scratch path with specific AE signal. Critical load repeated itself within proper range of testing parameters. Position 4. 9 N AE sig-nal appeared during several tests under different setting parameters, in combination with the scratch morphology, it clarified that the adhesion strength of as-deposited TiN film was 4. 9 N.