热处理对Ni-TiN纳米复合镀层结构和性能的影响

目的进一步提高脉冲-超声电沉积Ni-TiN纳米复合镀层的显微硬度,改善镀层的耐磨性。方法利用扫描电镜、X射线衍射仪、显微硬度计、摩擦磨损仪器,对经200~600℃热处理后Ni-TiN纳米复合镀层的表面形貌、内部组织结构、显微硬度和磨损性能进行检测,研究了热处理方式对复合镀层的表面形貌、晶相组织、显微硬度和耐磨性的影响。结果经300℃保温1.5 h后的镀层表面最为平整和光滑。同时镀层开始实现非晶态向晶态演变,并且镀层硬度最高,其值高达815HV。随热处理温度的升高,镀层晶粒变大,表面平整度降低。经600℃热处理,保温1.5h后,镀层的耐磨性最佳,磨损量仅为13.2 mg。结论经热处理之后,镀层硬度得到一定程度的提高,主要是TiN纳米粒子起到弥散和细晶强化作用。耐磨性得到有效改善,主要是由于镀层韧性、镀层和基体间的结合力得到提高,镀层形成一层致密的氧化膜的原因。

Effect of Heat Treatment on Structure and Properties of Ni-TiN Nano Composite Coating

The work aims to improve wear resistance of coating by further improving microhardness of Ni-TiN nano com-posite coatings electrodeposited by pulse-ultrasound. Surface morphology, microstructure, microhardness and wear resistance of Ni-TiN nano composite coatings were detected using scanning electron microscopy, X-ray diffractometer, microhardness tester and friction and wear instrument after heat treatment at temperature 200~600℃ . Effects of heat treatment manner on morphol-ogy, microstructure, microhardness and wear resistance of the composite coatings were studied. After heat treatment at 300℃for 1.5 h, the most flat and smooth coating surface was obtained. With the increase of heat treatment temperature, grains of the coating grew and its surface roughness decreased. Meanwhile, the coating began to transform from amorphous to crystalline state. In addition, the coating hardness was the maximum, 815HV. After heat treatment at 600℃ for 1.5 h, the wear resistance of the coating was the best, and the abrasion loss was 13.2 mg. The hardness of the coating is improved to a certain extent after heat treatment since TiN nano particles mainly has dispersion strengthening effect and fine crystal strengthening effect. The wear resistance is effectively improved since coating toughness as well as adhesion between the coating and substrate are im- proved, and a dense oxide film is formed.