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Thermal Fatigue Damage and Residual Mechanical Properties of WCu45/FeCr18Ni9 Steel Brazed Joint with NiCrSiBFe Filler Metal

Xia Chunzhi, Fu Linling, Du Wenchao, Xu Xiangping, Wang Xiling, Zou Jiasheng

Archives of Metallurgy and Materials

2021

Vol. 66, iss. 1

197--203

Thermal fatigue properties of WCu45/ FeCr18Ni9 steel brazed joint with Ni-Cr-Si-B filler metal were investigated. Results indicated that the fatigue damage of Ni-based joint was aggravated with the increased of thermal fatigue cycles times. Moreover, the fatigue cracks appeared in the brazing seam and FeCr18Ni9 steel side near the brazing seam, and the bending strength of the brazed joint decreased from 333 MPa of original joint to 160 MPa of having experienced 200 thermal fatigue cycles. The fracture characteristic of Ni-based joint underwent 200 cycles was identified as mixed ductile-brittle fracture under the combined effect of external bending load and internal fatigue damage.

A novel design of the combustion engine for improvement of the efficiency and durability

Drew J., Jankowski A., Siemińska B., Sławinski Z.

Journal of KONES

2006

Vol. 13, No. 4

453-466

For the purpose of the improvement of the efficiency of the combustion engine, the new solution which links in the advantage of the engine with the spark-ignition and the diesel engine is proposes. The creature of the solution consists in the realization the process of the combustion at the constant of the volume combustion chambers. It is realized with a piston stand during the period of combustion process. This permits on maximum pressure increasing and average indicated pressure. Advantages of this solution are self-evident. The enlargement of the efficiency is obtained, and finally - decrease of fuel consumption. Whereas at such itself average indicated pressure, the of maximum decrease of appears. This maximum pressure decrease causes decrease of mechanical loads of most essential engine parts, for which the pistons belong. The novel design of the engine is In order to reduce the thermal loads on the piston and the negative effects of thermal shocks, the novel construction based design was proposed, where during the time when the thermal loads are the most severe, the mechanical loads are isolated from the inertial loads and the inertial loads are non existent. Besides the reduction of the thermal loads additional gains in overall efficiency were obtained as the result of the combustion process with the piston stopped. That system forms the part of United States Patent No. 6,481.393 B1. Thermal shocks are reasons for high temperature gradients occurring in materials of engine components and sets, what in turn makes for high total stresses, even at lack of mechanical loads that accelerate damage of the engine components. With reference to heterogeneous elements like bimetals and from materials with covers, temperature gradients will be considerably greater and will represent what is due to different material properties. Experimental test results of thermal shocks for heavy-duty pistons of combustion engines are presented in the paper. Temperature measurement results on the crown and the skirt of the piston during the Diesel engine operating under different conditions are presented in the paper. Temperatures on the piston surface in the area of combustion chamber change in an every working cycle and these changes grow less with frequency (engine speed) increasing.