激光表面织构化对GCr15钢摩擦磨损性能的影响

本文利用Nd:YAG固体脉冲激光对GCr15钢样品表面进行了微坑织构化处理,考察了激光表面织构参数对其摩擦性能的影响,同时通过扫描电镜等对磨斑表面进行了分析.结果表明:与光滑面试样相比,经织构化处理的样品表面在干摩擦条件下虽然摩擦系数较高,但表现出了较好的抗磨性能;在贫油润滑条件下,织构面的摩擦系数与磨损均明显小于光滑面;在低载低速下较小孔径织构面摩擦系数较小,随着速度及载荷的增大,较大孔径织构面表现出更好的摩擦学性能.采用Stribeck曲线探讨了织构化表面与光滑面在贫油润滑下的润滑机理,结果表明织构面在试验条件下均保持油膜流体润滑状态.

残余奥氏体对GCr15钢强韧性的影响

轴承钢经不同温度奥氏体化后,在Ms点下等温,可得到不同数量和形状的残余奥氏体(A_R);随着薄膜状A_R增加,钢的强韧性提高;块状A_R在高应力作用下将大部分转变成马氏体,因而对改善钢的强韧性作用不大。

GCr15钢磨削开裂的特征及影响因素

通过磨削试验,研究了GCr15钢的磨削开裂特点及裂纹特征;再通过对其进行不同温度回火、-196℃深冷和酸浸等处理,进一步研究了这些因素对磨削开裂的影响。结果表明:GCr15钢磨削裂纹的出现具有延迟性,裂纹面以沿晶为主,具有氢脆断口特征;酸浸处理和深冷处理后磨削开裂倾向增大;随着回火温度升高,磨削开裂倾向减小;磨削开裂与氢致延迟性破裂有关。

Wear Performance of Laser Surface Hardened GCr15 Steel

In order to assess the new tribological properties of laser surface hardened GCr15 steel, the wear resistance between specimens treated with laser and those of conventionally hardened under dry sliding conditions was compared. The change of wear mechanisms in laser hardened GCr15 resulted in a distinct difference in wear rates. The results showed that quenched zones not only had sufficient depth of hardening and higher hardness, but had more retained austenite and finer carbides because of a higher degree of carbide dissolution. Laser surface hardened GCr15 steel specimens exhibited superior wear resistance to their conventionally hardened specimens due to the effects of the microstructure hardening, high hardness and toughness. The wear mechanism for both the laser quenched layer and conventionally hardened layer was highly similar, generally involving adhesive, material transfer, wear-induced oxidation and plowing. When conventionally hardened block specimens rubbed against the laser hardened specimens, the surface of conventionally hardened block specimens was polished. The microstructural thermal stability was increased after laser surface treatment.

Hot deformation behaviors and flow stress model of GCr15 bearing steel

The hot deformation behaviors of GCr15 bearing steel were investigated by isothermal compression tests, performed on a Gleeble-3800 thermal-mechanical simulator at temperatures between 950 ℃ and 1 150 ℃ and strain rates between 0.1 and 10 s-1. The peak stress and peak strain as functions of processing parameters were obtained. The dependence of peak stress on strain rate and temperature obeys a hyperbolic sine equation with a Zener-Hollomon parameter. By regression analysis, in the temperature range of 950-1 150 ℃ and strain rate range of 0.1?10 s?1, the mean activation energy and the stress exponent were determined to be 351kJ/mol and 4.728, respectively. Meanwhile, models of flow stress and dynamic recrystallization (DRX) grain size were also established. The model predictions show good agreement with experimental results.

Effect of electromagnetic stirring on metallurgical quality of GCr15 electroslag ingot

To further improve the metallurgical quality of electroslag remelting,remove the large inclusions in electroslag ingot and refine the solidification structure of electroslag ingot,an electroslag remelting furnace with electromagnetic stirring was designed,and the influence of different magnetic induction intensities on metallurgical quality of GCr15 electroslag ingot was studied.Inclusions with different sizes and types were analyzed by an ASPEX scanning electron microscope,and the morphology and composition of inclusions were further observed by a JSM-6510LV scanning electron microscope.The distribution of alloying elements on the cross section of electroslag ingot was analyzed by original position analysis(OPA).The results show that whether or not electromagnetic stirring is used,the inclusions in electroslag ingot are mainly composed of Al_(2)O_(3),MnS,MnS-oxide and other oxides,among which Al_(2)O_(3) is the most.Compared with an electroslag ingot without electromagnetic stirring,the number of inclusions decreases considerably,and the proportion of small inclusions increases while the proportion of large inclusions decreases when the electromagnetic stirring with remelting current of 1.1 kA and magnetic induction intensity of 62 Gs is applied.However,excessive electromagnetic force will cause the number and diameter of inclusions to increase again.Electromagnetic stirring has different effects on the segregation of different elements.Under the experimental conditions,the weak electromagnetic force with 1.1 kA and magnetic induction intensity of 108 Gs has little effect on the segregation of C,but decreases the segregation of P,and the excessive electromagnetic force aggravates the segregation of alloy elements.

Microstructural evolution of GCr15 steel during austenitizing and quenching considering C and Cr content

Microstructural evolution of GCr15 steels with different C and Cr contents during austenitizing and quenching was studied. Thermodynamic analysis of cementite dissolution was implied to obtain the critical temperature. The coordination number x in Fe_xCr_(3-x)C and the volume fraction of undissolved cementite were computed according to element conservation and equilibrium phase diagram. The M_S(martensite transformation temperature) was calculated by using empirical formula. The retained austenite content was calculated with further consideration of quenching temperature. The results showed that the coordination number and the undissolved cementite content were promoted by the austenitizing temperature and carbon content of the steel. Increasing Cr element reduced the coordination number.GCr15 steels with different components had nearly the same M_S when austenitization at 830 °C to 860 °C. The interaction of C and Cr complicated the evolution of M_S and retained austenite content. The results were in good agreement with the literature, which could guide to obtain specified retained austenite and/or carbides.

Alloying Effect of Lanthanum in GCr15 Bearing Steel with Tin and Antimony

Effect of tin and antimony on hot ductility of GCr15 bearing steel as well as interaction between lanthanum and tramp elements, were studied by simulator Gleeble-1500 and the fractures for the tested steels were analyzed using SEM and EDS. The results show that with increasing contents of tin and antimony elements, the hot ductility of GCr15 bearing steel was decreased. Lanthanum can reduce the harmful effect of tramp elements on the hot ductility of GCr15, which can react with antimony to form compound and segregate at grain boundary in steel. Lanthanum can refine the recrystallized austenite grains after deformation and subsequent martensite structure.

Effects of Suspension Casting on Solidification Process of GCr15 Steel Ingot

The mechanism of inoculation in the case of suspension casting process has been studied through solidification kinetics. The effect of suspension casting process on temperature field, solidification rate, temperature gap of crystallization, effective distribution coefficient of solute and nucleation frequency during solidification process in steel ingot were discussed on the base of experiments. It has been found that the suspension casting process can increase both cooling at and solidification rate of steel ingot, improve the temperature field and solute distribution, narrow the temperature gap of crystallication, and increase the nucleation frequency. Thus, the solidification time can be shorten, the solute can be well distributied, the shrinkage porosity can be reduced and the grain of crystallization can be fined.

The microstructural nanoindentation characteristics of different phases in precision annealed GCr15 steel

This study characterizes the mechanical properties and volume fractions of the different phases in precision annealed GCr15 steel using nanoindentation technology. Experimental results indicate that the nanoindentation hardness of cementite grains is between 14.15 GPa and 17.61 GPa,with a mean value of 15.40 GPa. This hardness is much higher than the hardness of ferrite grains. The nanoindentation hardness of ferrite is between 2.78 GPa and 4.89 GPa, with a mean value of 3.35 GPa. The volume fractions of the different phases were also determined using nanoindentation technology, and the volume fraction of cementite in the steel was identified as 15%.

K_d和D_d的关系及其在轧辊淬火中的应用

本文提出Gc_r15轴承钢盐水淬火时,水冷时间系数K_d与危险截面尺寸D_d的关系及其在轧辊淬火中的应用。

模铸法制备GCr15扁锭模拟与微观组织研究

采用Pro/E三维建模,通过ProCAST软件模拟了模铸法制备3.1t的GCr15扁锭的凝固过程,分析了钢锭充型过程中温度场及固相率,预测了钢锭可能产生缩松和缩孔缺陷的位置,研究了其宏观铸造组织。利用扫描电镜(SEM)观察了其微观组织,使用屏显式材料端面高温摩擦磨损试验机研究了微观组织结构对摩擦磨损特性的影响。结果表明,钢锭的凝固顺序:轴向上由钢锭底部向钢锭帽头处推进,径向上从型壁向钢锭的中心逐步进行;钢锭的缩孔集中在帽头部位,钢锭中心易产生缩松;条状、六方棱柱状的M7C3型碳化物对GCr15铸锭的耐磨性影响显著。

Effect of axial static magnetic field on cleanliness and microstructure in magnetically controlled electroslag remelted bearing steel

The effect of the axial static magnetic field(ASMF)on cleanliness and microstructure in magnetically controlled electroslag remelted GCr15 bearing steel ingots was investigated experimentally.The results show that a magnetically controlled spin-vibration induced by the interaction of the ASMFs and the remelting current exists at the consumable electrode tip,resulting in thinner liquid melt film and smaller droplets.With the increase in magnetic flux density,the optimization effect of ASMFs on electroslag remelting process increases and reaches the peak with a 40 mT ASMF,then decreases.The cleanliness of the ingots was improved,and the count of inclusions larger than 5μm was reduced.The microstructure of the ingots processed with a 40 mT ASMF was significantly refined.The depth of the metallic molten pool was reduced from 45.2 to 17.5 mm with the application of 40 mT ASMF.The tensile strength,impact toughness,and Rockwell hardness of the ingots obtained under the 40 mT ASMF were significantly improved.The mechanisms of the spin-vibration occurring at the electrode tip end were interpreted in detail to elucidate the effect of ASMFs.

Hot Deformation Behavior of GCr15 Steel

Hot deformation behavior of GCr15（ASTM 52100） steel was investigated using single-hit compression tests on Gleeble-1500 simulator at the temperature range of 850-1 100 ℃ and strain rate range of 0.1-10 s-1.The flow stress constitutive equation of GCr15 steel during hot deformation was determined by stress-strain curves analysis on the basis of the hyperbolic sine equation.And the models of dynamic recrystallization fraction and dynamic recrystallization grain size of GCr15 steel were established by the measured curves and microstructure observation in different experimental conditions.The mean activation energy and the time exponent of dynamic recrystallization kinetics equation in the range of experimental conditions were determined to be 356.2 kJ/mol and 2.12,respectively.Meanwhile,the flow stress model was also established by the method of allocating flow stress curve with three main stress values,the saturation stress,the steady state stress and the stress when strain is 0.1.The flow stress curves predicted by the developed models under different deformation conditions are in good agreements with the measured ones.