【作者】 陈宁；

【导师】 黄兴元； 廖钟亮；

【作者基本信息】 南昌大学 ， 机械工程， 2009， 硕士

【摘要】 激光熔覆技术是表面改性技术中的一种,主要特点是可以提高机件的表面硬度、耐磨性、耐腐蚀等性能,得到细小的晶体组织结构,改善了机件的综合机械性能,而且能修复因磨损而引起的失效零件,延长零件的使用寿命。本文以模具工业中常用的T10钢为主要研究对象,重点研究在模具材料表面激光熔覆Ni基合金材料的工艺过程,及熔覆层的显微组织、裂纹的状况,同时研究了在Ni基合金中加入Wc硬质相后的熔覆层的性能和组织结构的改变情况。实验显示:激光熔覆后主要由四部分组成:熔覆区域、结合区、热影响区和基体。熔覆层的显微组织主要为粒状、棒状的树状晶结构,出现该组织主要是受激光快速加热和快速冷却凝固影响的原因。在激光熔覆过程中,各处的加热速度和冷却速度存在很大的差别,使得熔覆层的显微硬度分布也不是很均匀,在熔覆层的次表面具有最高的硬度可达872.6HV0.1左右,耐磨性能也最好,提高了尽75%左右,这是晶粒细化和均匀化的所造成的。加入Wc硬质相后,熔覆层的显微硬度改变不明显,耐磨性能得到了很大的提高,但是由于加入的是硬质相,相应的脆性也会增大,易产生裂纹,这就需要合理的选择工艺及参数来尽量减少裂纹。试验利用扫描电镜观察分析、显微硬度测定、耐磨性测试及正交试验分析等手段,研究激光功率、扫描速度、离焦量参数对熔覆层的显微硬度、耐磨性和显微组织的影响规律。试验结果表明:在其他条件不变的情况下,激光功率的增加,熔覆层的显微硬度先增加后减小,熔覆件的耐磨性能也有一个先增大后减小的过程。以激光功率、扫描速度和离焦量三个工艺参数作为影响熔覆层性能的水平因素,并选择合适的结果量进行正交试验,通过对实验结果的分析可获得熔覆层显微硬度和耐磨等性能优良的激光加工工艺参数。更多还原

【Abstract】 Laser cladding is one of the surface treatments. It can strengthen the surface hardness、wear resistance and corrosion resistance of materials and parts, thinning grain and microstructure ,improve surface properties of materials.T10 steel, a frequently used material in mould industry, is studied principally in this paper, and the emphasis is put on the process of laser cladding Ni alloy on the mould steel and the microstructure, the crack, the overlapping of cladding layers, as well as the capability and microstructure of Ni alloy with WC laser layers. The experiment result shows that there are three layers: the coating region, bonded zone and heat affected zone. Under the proper laser cladding parameter, nice union resistance cladding layer can be obtained. The microstructure of cladding layer is composed by clavoid form and grainy cellular crystals, due to the laser speediness calefaction and cooling. In the cladding process, the speed of calefaction and cooling is different, so the distributing of hardness is asymmetry, the rigidity can be up to 872.6 HV0.1 in the secondary surface, the wearable properties is also the highest. After the adding of Wc, the hardness of laser layer has little changing, but the wearable properties had been enhanced greatly, with the enhancing of frangibility, so the choosing of cladding parameter is needed.The influence of laser power, scanning speed and off-focus to the cladding layer’s hardness, surface wearable properties and microstructure were studied by the use of scanning electron microscope, micro hardness testing techniques, wearable properties testing and the orthogonal experiment analysis and so on. The result shows that the micro hardness of the cladding layer is increased firstly and the then droped, and so is the wearable properties of material. This is resulted by the difference of energy density which bring to the different size of crystal granule. As the scanning speed-becoming augment ,the clading layer’s hardness and wearable properties have the same changing process.The three affecting factors of laser power, scanning speed and the defocus amount has been chosen in the orthogonal test. Through the analysis of experimental results, we get the laser cladding parameter adapt to produce actually in the hardening and surface wearable properties.更多还原