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1.
The effects of electron beam surface hardening treatment on the microstructure and hardness of AISI D3 tool steel have been investigated in this paper. The results showed that the microstructure of the hardened layer consisted of martensite, a dispersion of fine carbides and retained austensite while the transition area mainly consisted of tempered sorbite. Also, the microhardness of the hardened layer on the surface increased dramatically compared to that of base material. Finally, the hardening response of AISI D3 tool steel to electron beam surface treatment is closely related to the scanning speed of the electron beam. 相似文献
2.
Fatigue behaviour of induction hardened parts is largely dependent on the correct combination of hardening depth and the magnitude and distribution of residual compressive stresses in the surface layer. The objective of this work was to study experimentally the residual stresses at the surface layer of induction hardened cylindrical specimens. Two microstructures, quenched-tempered and normalised were investigated. The process parameters of induction hardening were varied to give a constant hardness penetration depth. The residual stresses were measured using the X-ray diffraction method. The investigated induction hardened samples showed a constant biaxial residual stress-state at the surface. The directions of the principal stresses deviated slightly from the defined circumferential and longitudinal directions. However, the shear stresses at the surface were of a small magnitude. This experimental investigation showed that the process parameters of induction hardening influence the residual stress-state of hardened parts to a great extent. 相似文献
3.
《Materials Science & Technology》2013,29(11):1310-1316
AbstractA study of electric contact surface treatment to ductile iron has been carried out. This technology was based on the application of the contact resistance heating between the electrode and workpiece. For comparison, the experiments of induction hardening to ductile iron were studied. The microstructure, microhardness, surface residual stress and wear properties were investigated using optical microscope, scanning electron microscope, X-ray diffraction, Vickers microhardness and rolling contact wear tests. Electric contact surface treatment resulted in the formation of fine ledeburite (white bright layer) and martensite in the ductile iron surface, in which the hardness in these areas was higher than that of induction hardened surface. The wear test results showed that the ductile iron surface after electric contact surface treatment had better wear resistance owing to the fine microstructure, high hardness and residual compressive stress. 相似文献
4.
NungheeRYU SunggoonKANG 《材料科学技术学报》2002,18(1):17-20
The effects of laser hardening parameters such as beam power,beam diameter and scanning rate on microstructure and mardness of 9CrSi steel were investigated.The microstructure of the surface layer of 9CiSi steel was changed from pearlite to martensite,retained austenite and carbide by laser hardening .The depth of the hardened layer increased with increasing laser energy density and the surface hardeness increased by 3-5times as high as the untreated steel.The laser hardened surface had good wear resistance due to martensite and carbide in the surface layer.The wear mode at low speed was abrasive,while the wear mode at high speed was adhesive. 相似文献
5.
《材料与设计》2015
To improve the distribution of the hardened layer and avoid potential defects, the effects of induction hardening parameters on the hardened layer were researched using the finite element method (FEM). A FEM model of single coil induction hardening was built, and temperature curves on the surface region of a ball screw were attained by numerical simulation. The hardenability and phase transformation of 55CrMo steel were researched by experiment. The simulation and experimental results show that the temperatures Ac1 and Ac3 rise with increasing heating rate. Non-uniformity of temperature at the groove region can lead to non-uniformity of austenitization and hardness. High temperature can result in cracks, coarse grain size and overheating defects at the groove tip. Martensite produced during cooling transforms into tempered martensite due to the residual heat, and the remaining austenite transforms into martensite at a low cooling rate. A 5010-type ball screw cannot attain a hardened layer with the thickness of 2.5 mm at the groove bottom without defects at the groove tip by single coil induction hardening. Multiple induction coils with a certain gap would be helpful to improve the uniformity of temperature and hardness. 相似文献
6.
10 Induction hardened discs with two initial hardness levels were used for exploring the influences of the variation of initial hardness as well as induction hardening (IH) recipes on the heat treatment distortions and hardening depth. The results show that for the same initial hardness, the larger the energy input, the higher the distortion size as well as the hardening depth. For a given induction hardening recipe, the increase in initial hardness leads to a deeper hardening depth but a smaller distortion. One disc was selected for the residual stress investigation in three orthogonal directions by neutron diffraction (ND). The corresponding stress-free lattice spacing d0 was measured from the same material using both ND and X-ray diffraction (XRD) methods. The ND results show that the variation of d0 in the hardened layer is significant and should be taken into account for stress calculation. However, regarding the core region, the d0 value measured by XRD is more reliable. Accordingly, a combination of the ND-measured d0 profiles in the hardened layer and the XRD-measured d0 value in the core was adopted for the determination of residual stress distributions. 相似文献
7.
Dieter Schneider Berndt Brenner Thomas Schwarz 《Journal of Nondestructive Evaluation》1995,14(1):21-29
Ultrasonic surface waves are suitable for the characterization of surface hardened materials. This is shown on laser hardened turbine blades. The martensitic microstructure within the surface layer of surface hardened steels has a lower surface wave propagation velocity than the annealed or normalized substrate material. Because the propagation velocity depends on the ratio of layer thickness to wavelengthd/, its measurement allows the determination of the hardening depth. If the surface wave frequency is high enough, the surface wave propagates mainly within the hardened layer. A correlation of the surface wave velocity to the surface hardness has been found. Because the variation of the surface velocity in hardened steels is small, a high measurement accuracy is necessary to obtain the interesting hardening parameters with sufficient certainty. Therefore, a measuring arrangement has been developed where laser pulses, guided by optical fibers to the surface hardened structure, generate simultaneously surface wave pulses at two different positions. The two ultrasonic pulses are received by a piezoelectric transducer. The surface wave velocity is obtained from the time delay between these pulses which is determined by the cross-correlation method. To evaluate simultaneously surface waves with different penetration depths from the same signal acquisition, digital filtering has been used in connection with the cross-correlation. 相似文献
8.
采用热磁分析、显微硬度分析与直读光谱分析等相结合的方法,对无碳化物贝氏体钢进行渗碳后的深冷处理工艺优化。结果表明:无碳化物贝氏体钢在1193K渗碳空冷后,测试有效硬化层样品的热磁曲线,可以得到有效硬化层的深冷处理温度宜低于134K。经123K深冷处理和463K回火,有效硬化层残留奥氏体含量约为12.2%(质量分数)。通过深冷处理使渗碳钢近表面层得到显著硬化,再经低温回火使近表面层硬度均达到810HV_(1.0)左右,渗碳钢的硬度梯度分布趋于合理。 相似文献
9.
Makoto Hino Minoru Hiramatsu Koichi Akiyama Hitoshi Kawasaki Masato Tsujikawa Makoto Kawamoto 《Materials and Manufacturing Processes》1997,12(1):37-46
A high powered YAG laser with kaleidoscope for surface modification was applied to the surface hardening of carbon steels containing 0. 18-0.54 wt% C without the absorbents, and the relationships between laser processing and surface hardening were investigated by hardness and microstructure. The structure of the hardened zone underwent complete martensitic transformation in all of the carbon steels tested, and its hardness increased with greater carbon content. Under identical irradiated conditions, the hardened zone expanded with increasing carbon content. A hardened zone extending from the surface to a depth of 1.0 mm was obtained at a laser power of 1.0 kW and a scanning speed of 1 mm/sec. It was found that in the surface hardening of carbon steels, a high powered YAG laser can be used to control the hardened zone by selecting the appropriate irradiation conditions, however, the hardened zone was affected by the assistant gas and the flow rate. 相似文献
10.
We have determined the kinetic parameters of interaction of VT1-0, VT5, OT4-1, and VT16 alloys with a rarefied gaseous medium.
We have established the interrelation between the parameters of chemical heat treatment (T, τ, and p, the interstitial hardening of surface layers of the metal, and its phase and structural state. The conditions of saturation
(T, τ, and p) being equal, hardened layers differing in the microhardness and thickness of the layer H and l are formed on titanium alloys of different structural classes. Single-phase VT1-0 and VT5 α-titanium alloys as well as OT4-1
pseudo-α-alloy are the most sensitive to the conditions of gas saturation: the hardness and its gradient in the hardened layer
grow significantly. As the β-phase content increases (VT16), changes in the parameters of chemical heat treatment affect less
the hardness of the surface layer, but the depth of the hardened zone grows with temperature T and time τ.
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Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 2, pp. 63–70, March–April, 2005. 相似文献
11.
盐浴复合(QPQ)技术为公认的能同时提高金属材料耐腐蚀性和耐磨性的表面改性技术,但其推广使用受到环保制约。为开发绿色高效表面改性技术,探索了离子氮碳氧三元共渗(PNCO)技术,并与QPQ技术改性效果进行了对比研究。选择45钢为原材料,分别采用PNCO技术和QPQ技术进行表面改性。利用光学显微镜及扫描电子显微镜、XRD、显微硬度计、摩擦磨损试验机、浸泡腐蚀实验对两种表面处理试样的截面显微组织、物相、表面及截面硬度、耐磨性和耐腐蚀性进行测试和分析。结果表明,在510℃×4 h工艺条件下,PNCO处理获得的化合物层厚度为20.14μm,有效硬化层厚度为59μm,截面最高硬度为760HV_(0.05),磨损率为1.39×10^(-3)g·N^(-1)·m^(-1),腐蚀失重率为0.39%。XRD结果分析表明,PNCO处理后渗层形成了Fe_(x)N化合物和以Fe_(3)O_(4)为主的氧化物相。PNCO和QPQ对比研究发现,两者表层硬度、耐磨性及耐腐蚀性均相近。本研究为绿色高效表面改性技术提供了可行的研究方向。 相似文献
12.
《Materials Chemistry and Physics》1988,19(3):205-214
Some predictions on the hardness and hardening depths on laser heat treatment of steels can be obtained when specific characteristics of both laser processes (heating and cooling rates) and laser heat treated steels (microhardness profiles) are taken into account. Some controlled surface temperature laser heat treatments have been carried out with a medium power c.w. CO2 laser on a medium carbon steel (AISI/SAE1045), allowing these predictions to be tested. In particular, knowing the surface temperature has enabled an analytical algorithm to be used to describe thermal processes and a simple exponential expression to be employed to carefully predict the hardened case depth. 相似文献
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目的研究感应淬火对曲轴扭转疲劳性能的影响,为曲轴的设计和制造工艺调整提供技术参考。方法开展淬火曲轴和未淬火曲轴的扭转疲劳强度试验,利用升降法得到疲劳试验结果,从试验数据和微观组织等方面开展分析和讨论。结果未经过淬火的曲轴在99.9%存活率下的扭转疲劳极限为967.6N·m,经过感应淬火的曲轴在99.9%存活率下的扭转疲劳极限为1361.2N·m。感应淬火后曲轴的表面形成深度约3.5 mm的淬火层,平均硬度为HV0.5600,金相组织为细针状马氏体。曲轴的失效情况均为连杆颈油孔处开裂。结论 38MnVS6非调质钢曲轴在感应淬火后的扭转疲劳极限提升了约41%,曲轴油孔内壁的加工缺陷是形成裂纹源的主要原因,对曲轴淬火层区域的油孔内壁进行一定的表面处理,可进一步提高曲轴的扭转疲劳强度。 相似文献
15.
《Materials Science & Technology》2013,29(11):1069-1073
AbstractSintered and precipitation hardened Cu–25Cr (wt-%) contact alloys were prepared and their properties related to those of a precipitation and strain hardened reference alloy. The evolution of microstructure during sintering, solution heat treatment, and precipitation hardening was studied, in particular with respect to precipitate morphology and growth. The influence of microstructure on the hardness, strength, and electrical conductivity of Cu–25Cr alloys was evaluated. The relative importance of precipitation and strain hardening has been clarified, and it is shown that the contribution of the precipitation effect is dominant. The importance of monitoring the evolution of microstructure with respect to long term stability of Cu–Cr contact alloys is emphasised.MST/999 相似文献
16.
V. A. Dutka 《Journal of Superhard Materials》2008,30(5):338-348
The paper presents some results of numerical prediction of the possibility of hardening a working surface of a steel holder of a carbide tool through quenching in aqueous solutions of salts and bases upon the insert-to-holder induction brazing. The investigation is performed using a previously developed computer model of a temperature field in a carbide tool during its induction brazing, air cooling as it is carried from the induction heater to a quenchant, and cooling in the quenchant. Predictive estimates of the hardened surface layer thickness and the hardness of the holder working surface are made for various quenching conditions. 相似文献
17.
The problem of formation of plastic zones in case-hardened metallic bodies due to contact overloading is studied both experimentally and numerically. Metallic materials exposed to surface hardening demonstrate spatial variation of the material hardness and yield strength with a decreasing profile with depth and belong to the class of so-called plastically graded materials. The presented experimental program employs micro-Vickers hardness tests to map the variation in material hardness and corresponding yield strength for both virgin and loaded case-hardened specimens made of a chromium tool steel. It is shown that, depending on the profile of the yield strength in the near-surface zones and contact parameters, a plastic deformation can originate underneath the hardened layer. The distribution of the effective plastic strain extracted from the micro-hardness increment measurements are found in good agreement with the results of finite element simulations of a plastically graded material subjected to similar loading conditions. Numerical analysis reveals significant perturbations in the stress field distribution within the hardened layer due to formation of a closed-shaped plastic zone in the gradient layers, including development of a tensile stress on the boundary between the elastic and plastic zones as well as an overall increase in the effective stress intensity. It is shown that the hardened layer behaves similar to an elastic beam on a compliant foundation. These stress field perturbations in the hardened layers with low deformation capacity can greatly affect the durability and serviceability of surface treated mechanical parts. 相似文献
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This paper describes a novel process called “Dot Matrix Hardening” as applied to Ol, D2 and AISI 4340 steels. This process uses a pulsed laser (particularly an Nd:YAG laser) to create a uniform distribution of transformation-hardened spots to cover only a certain percentage of the desired surface. Due to significantly reduced energy input, wear resistance can be imparted to thin and intricate parts without distortion. In addition, with the use of a coupled fiber optic beam delivery system, this process provides greater flexibility compared to conventional CO2 laser hardening for a number of applications. The use of an Nd:YAG laser also eliminates the need of absorptive coating required for hardening with a CO2 laser. With optimized processing parameters, a relatively uniform hardened layer is obtained within the hardened spot, with a thickness of about 60 um and hardness values around 800 HV100. The sliding wear test results show that the wear resistance of Ol samples with only 20-40% area coverage of laser-hardened spots is similar to the 100% covered laser dot hardened sample as well as the furnace hardened (Re 60) sample. 相似文献