Advanced Materials Research Vols. 154-155

Abstract: Steel 35CrMo is widely used to produce the principal axis of machine, but the principal axis is often abraded or scratched during its service. The CoCr coating produced by electro-spark deposition on the machine principal axis of 35CrMo can solve the problem and resume its application. In this study, the interface behavior of joint between the CoCr coating and the 35CrNo steel substrate was studied. The microstructure of CoCr coating was also observed and analyzed by using a scanning electron microscope with an energy dispersive X-ray spectroscopy analysis. A narrow layer of elements diffusion containing Co0.72Fe0.28, CoCr and Co7Fe3 was detected in the bonding interface between the CoCr coating layer and the 35CrMo steel substrate. The CoCr coating with higher microhardness was obtained on the substrate. The results reveal that a joint between the CoCr alloy and the steel 35CrMo substrate with stable quality can be obtained by electro-spark deposition.

Abstract: On the property of repeated impact load, the attrition, hardening and plasticity warp of the laser cladding sampling were researched by using stress wave spread theory. Results show that under repeated impact loads, stress wave occurs on the metallurgical joint surface of the coat and the basis, forming stretch wave that causes coat slitting and angle splitting. The micro-pits failure and deep exfoliation occur on the coat surface because of the stress centralization. The accumulation of impact load energy cause hardness change and plasticity warp.

Abstract: Use of Low-chromium white cast iron as matrix, WC as reinforcement particles, in conditions of Quartz sand in ordinary water glass dry, non-vacuum, using self-made penetration compound was prepared by WC particles reinforced surface composite material with superior wear resistance, is 2.73 times that of high chromium cast iron composite layer hardness can reach HRC60 or more. Smooth casting surface roughness, dimensional accuracy is more accurate, composite layer and substrate is good.

Abstract: The oxy-acetylene flame spraying is a new kind of the spraying technology which is developed in recent years. The ultra-high strength is the pivotal structural material in aviation. The oxy-acetylene flame spraying method that is used to mend aeronautic parts made by ultra-high strength steel is studied in this article. The spraying technology of ultra-high strength parts made by 30CrMnSiNi2A steel is introduced.

Abstract: In this paper, back propagation neural network was used in the optimum design of the hot pressing parameters of an advanced ZrO2/TiB2/Al2O3 nanocomposite ceramic tool and die material. The BP algorithm could set up the relationship well between the hot pressing parameters and mechanical property of nanocomposite ceramic tool and die materials. After analyzed the predicted results, the best predicted results were the sintering temperature was 1420°C and the holding time was 60min. Under these hot pressing parameters, the best flexural strength and the best fracture toughness of the material could be obtained.

Abstract: Laser transmission joint between biocompatible, dissimilar materials have the potential for application in biomedical and their encapsulation process. This paper is devoted to laser transmission joint between 0.1mm thick PET films and 0.1mm thick Titanium using near-infrared diode lasers. Response surface methodology (RSM) is used to develop mathematical models between the joining process parameters. The developed mathematical models are tested for adequacy using analysis-of-variance (ANOVA) method. In addition, the main effect of each parameter and the interaction effects with other process parameters are analyzed. Finally, the experimental results agree with those predicted indicate that the developed mathematical models can predict the responses adequately.

Abstract: This study proposes a novel optical technique and method for in-situ roughness measurement. The speckle image was obtained by illuminating a laser beam and the reflected laser pattern image from a surface was binarizd and examined. The intensity distribution of binary image utilizes the combined effects of speckle and scattering phenomena. A new parameter of intensity distribution of binary image, Sd BD has been proposed and the surface roughness parameter Ra of machined surfaces (ground) were correlated experimentally. Measurement results demonstrate an excellent correlation between the SdBD and Ra with correlation coefficient of 0.9706. The practicality of the proposed method to in-situ roughness measurement was applied to six samples from roughness Ra 0.2 to 6.25μm (0.3 λ and 10 λ, where λ is diode laser wavelength) of steel through grinding process.

Abstract: The rolling tests of railway rail were performed using a JD-1 wheel/rail simulation facility without any lubricant. The failure behaviour of rail rollers with different materials, was investigated in detail by examining wear volume and wear scar using optical microscopy (OM) and scanning electronic microscopy (SEM). The results indicate that rail material with a high hardness appears less plastic flow after rolling test. When the plastic flow is small, the wear resistance of material appears better. However, the crack propagation is more significant and fatigue damage is more severe. There is a mutual competitive relationship between wear and surface fatigue crack. A high wear rate can reduce rolling contact fatigue damage by removing constantly surface cracks. The analysis shows that U71Mn rail is more suitable for the high-speed railway.

Abstract: According to the actual characteristics of semi-steel steelmaking of PZH steel, a static model for prediction of the oxygen blow amount and consumption of auxiliary material is established, and an end-point prediction model based on carbon content and temperature of sublance is given. This paper introduced the calculating principle and basic structure about above two models detailed. The results show that, the static model has certain accuracy and reliability of these models are illustrated by actual application.The static model might provide immediately the predicting optimum auxiliary material amount and the oxygen blow amount for operator, which direct the operation in time. The end-point prediction model might give real time prediction for the carbon content and temperature on BOF Endpoint, which has high hitting ratio.

Abstract: This study is to investigate the wear behavior of carburized JIS SNCM 415 Ni-Cr-Mo steel being cryotreated and followed by carbide spray coating for achieving improvement in wear resistance. Comparative specimens of JIS SNCM 439 steel were quenched and tempered to 45HRC to obtain a similar surface condition as the carburized JIS SNCM415 samples. The thickness of WC/Co coatings of 125 μm was deposited with the use of high velocity oxy-fuel (HVOF) process. The microhardness of the WC/Co coatings has been found to achieve 1025±75 HV. A series of wear tests have been carried out on steel samples subjected to various conditions under 95.9N with 180 rpm on a dry block-on-roller tester. From the result of 12 hr wear tests, the mass loss of carburized SNCM 415 steel through cryotreatment was 0.025 g improved from 0.05g of steel without cryotreatment. In addition, the mass loss of carburized SNCM 415 specimen under cryotreatment and HVOF process was further decreased from 0.025 g to 0.002 g. The mass loss of comparative JIS SNCM 439 steel coated by the HVOF process was decreased to 0.002 g from 0.045 g of steel without coating. The results clearly establish that cryotreatment and HVOF process significantly improve the surface hardness and wear resistance of carburized JIS SNCM 415 steel.