共查询到19条相似文献,搜索用时 140 毫秒
1.
2.
3.
4.
针对高铬铸铁铸造组织粗大,强韧性差,容易开裂的问题,进行了高铬铸铁粉末激光熔覆实验,对熔覆层的显微组织和硬度等性能进行了检测与分析,研究了不同扫描速度对熔覆层显微组织和硬度的影响,分析了多道搭接区和多层堆积区熔覆层显微组织的演变规律,揭示了多层堆积横截面的硬度分布规律。研究结果表明:通过激光熔覆可以获得晶粒细化、组织致密、无裂纹与气孔等缺陷、硬度高(可达580 HV0.2)的高铬铸铁熔覆层。将该工艺应用到零件表面强化领域,将大大提高零件的性能和使用寿命。 相似文献
5.
利用常压等离子相变硬化设备对灰口铸铁进行了表面相变硬化处理,处理后铸铁熔凝层的显微组织为初生奥氏体+莱氏体,固态相变硬化层的组织为隐针马氏体+残余奥氏体+片状石墨和少量磷共晶,铸铁的表面硬度明显高于基体硬度,并明显提高了灰口铸铁材料的耐磨性和使用寿命。 相似文献
6.
7.
8.
9.
本文利用超声频微锻造机构对45钢激光淬火层表面进行了微锻造处理。利用OM、SEM观察了微锻造对45钢激光淬火层表面组织的影响;利用显微硬度计与洛氏硬度计研究了微锻造后45钢激光淬火层表面显微硬度,硬化深度方向的显微硬度。结果表明:高频微锻造处理后,45钢激光淬火形成的明显而规则马氏体组织被锻碎,表面晶粒明显细化。表面显微硬度提高了11.4%,激光淬火强化区深度方向的显微硬度影响深度为0.2 mm,其中0.1 mm处硬度提高了10.0%,0.2 mm处提高了4.5%。 相似文献
10.
为了提高SKD61模具钢表面的硬度和抗疲劳性能,采用激光熔凝处理方法对模具钢进行表面强化,利用光学显微镜、扫描电镜及附带的能谱仪等分析了SKD61钢激光熔凝处理区的显微组织和化学成分,测试了不同区域的显微硬度,并对处理后的模具进行使用试验。结果表明:激光熔凝处理后SKD61钢组织分为熔凝区、热影响区和基体三层,熔凝区组织为极细的等轴晶和柱状晶,消除了夹杂相,合金元素基本均匀分布;与常规热处理相比,熔凝区的显微硬度显著提高;经激光熔凝处理的SKD61钢顶盖压铸模具的使用寿命提高了1倍以上。 相似文献
11.
This paper reports a study of the influence of surface oxidation on the wear resistance of ductile iron, grey iron and vermicular iron during dry sliding friction. The mechanisms of wear are also reported. This study shows that the effect of surface oxidation (formed under normal atmospheric conditions) on the wear rate depends on the complex functions of graphite morphology and matrix structure. Generally the presence of surface oxidation decreases the wear rate of grey iron but increases the wear rate of ductile iron and vermicular iron when the cast iron has high hardness. This trend is reversed for low hardness cast iron. 相似文献
12.
Corrosion and wear resistance characteristics of NiCr coating by laser alloying with powder feeding on grey iron liner 总被引:6,自引:0,他引:6
To reduce the mixed fuel induced excessive wear of the cast iron engine cylinder liners, research on laser alloying of NiCr alloy with powder feeding was performed to locally change both the composition and the microstructure of the liner. The research indicated that laser alloying of 75Ni25Cr on grey cast iron liner demonstrates sound alloying layers free of cracks and porosities. The microstructure of the alloyed layer is composed of pre-eutectic austenite and ledeburite. The alloying element Ni is mainly located in the austenite, while Cr is mainly in cementite. The average hardness is HV0.2500. The corrosion resistance of the alloyed layers in diluted H2SO4 solution and NaOH solution is dramatically improved compared to the grey cast iron. The relative wear resistance of the laser-alloyed 75Ni25Cr layer is 4.34 times of that of the grey cast iron. The improvements on the corrosion and wear resistance of the cast iron are attributed to the composition and microstructure change by laser alloying of 75Ni25Cr. Laser alloying can be a good solution to improve wear and corrosion resistance of the grey iron liners in mixed fuel environment. 相似文献
13.
14.
The surface of nodular graphite cast iron samples was melted by 50% overlapping passes from a 3 kW CW CO2 laser. The objective was to modify the microstructure and improve the hardness and erosion resistance of the surface. The results showed that laser melting led to complete dissolution of the graphite nodules which on solidifying created an inter-dendritic network of ledeburite eutectic with a very fine structure, good homogeneity, and high hardness. Sand particle erosion experiments were carried out at impingement angles of 30°, 60°, and 90° using angular particles of size between 300 and 600 μm. The velocity of the sand particles was 50 m/s, which was controlled by the gas pressure and measured by the double-disc method. The erosion resistance of the laser treated nodular cast iron was 110 times greater than the untreated material. The erosion mechanism of the untreated nodular cast iron under normal and oblique angles was by severe plastic deformation and ploughing; whilst the mechanism for the treated specimens was by fatigue cracking. The improvements of erosion resistance after laser treatment were considered due to the very fine structure, high micro hardness (650 Hv0.1) with the resistance to plastic flow and to the dissolution of the graphite nodules. 相似文献
15.
16.
In order to investigate the effect of a spot continual induction hardening (SCIH) process on the tribological performance of grey cast iron with a curved surface, dry sliding wear tests were performed under different loads. The curved surface structure of the workpiece and feed velocity of the inductor were considered important influence factors. X-ray diffractometry (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) were used to investigate the phases, compositions, and morphologies of grey cast iron after the SCIH process and tribological tests. The results showed that the wear mechanism of grey cast iron was always adhesive and abrasive wear at different loads when the workpiece was not strengthened. In the case of partial strengthening, the wear mechanism changed from adhesive and abrasive wear to fatigue–exfoliative wear with increasing load. Oxidative wear always appeared as the dominant wear mechanism when the workpiece was completely strengthened. The wear resistance of the concave surface was always larger than that of the convex surface under the same feed velocity of the inductor. Relatively low feed velocity of the inductor in the SCIH process can optimize the wear resistance of grey cast iron with a curved surface. 相似文献
17.
Erosion resistance of four types of cast iron of different microstructures and graphite morphologies (viz., grey cast iron, compacted graphite iron, spheroidal graphite iron and austempered ductile iron) was evaluated in three different erosive media. Results indicate that austempered ductile iron has the highest erosion resistance in all three media, followed by spheroidal graphite iron, compacted graphite iron and grey cast iron, in that order. Graphite morphology has a significant effect on the erosion resistance of these irons in quartz-water and iron oxide-oil slurry. However, the matrix microstructure determines the erosion resistance of these irons in quartz-oil slurry. The parameter H/E (which is the ratio of the Brinell hardness number to Young's modulus of the material) has been found to be a good indicator of erosive wear in quartz-oil slurry. 相似文献
18.
高铬铸铁基碳化钨粒子增强表面复合材料的研制 总被引:8,自引:0,他引:8
采用熔覆铸造工艺在灰铸铁,球墨铸铁表面得到一层高铬铸铁基WC粒子增强复合材料,并研究了影响复合材料质量的工艺因素,复合材料的组织和耐磨粒磨缶性能以及在农机具上的应用。 相似文献
19.
冷硬铸铁轧辊辊身硬度高,耐磨性好,被广泛用于板材、线材和棒材轧机上,但同时,它也存在难以被切削加工的问题,本文探讨了冷硬铸铁轧辊的切削性能,分析了冷硬铸铁轧辊切削加工困难的原因,对冷硬铸铁轧辊切削加工工艺进行了改进,提高了切削加工的质量,并且减少了切削加工的时间。 相似文献