Research On The New Material For The Plunger Tip

This project is the study of aluminum bronze with high strength and excellent wear resistance. The main purpose of the present work is to improve the performance of the alloy to replace beryllium bronze. So we will solve the problem that the service life of the plunger tip made by ourselves is short and high-performance ones need import.In view of the work condition and failure analysis of the plunger tip, compared the microstructure of the different materials, aluminum bronze with high strength and excellent wear resistance was chosen as the novel material for the plunger tip. By the optimization of the smelting process and chemical composition, appropriate heat treatment and Refinement, the material for the plunger tip with high strength and excellent wear resistance was prepared, and the wear and thermal fatigue performance of which were tested. The microstructure required:fine grains and microstructure, tough matrix with uniformly distributed hard phase. The project design:by controlling the Al content, the ratio of hard phase to soft phase was increased. Fe, Ni and Mn were involved in the formation of κ phase, and could improve the stability of β. In the work, the Ni content was reduced, and the solid solution strengthening of Mn was used. By appropriate heat treatment and refinement, both the strength and toughness was gained.The chemical composition of the alloy determined:Al 10～10.5%, Fe 4%, Nil%, Mn 1-2%. To improve the strength and hardness, the most appropriate heat treatment process is 900℃2h and water quenching+375℃ 2h and air cooling. Considering the plastic and toughness, the optimum content of the refining agent is 0.6%. The final microstructure of alloy:β’+a bit of a and γ2 formed the matrix with the fine and uniform κ phase. The performance of the alloy:Rm:814MPa, Rpo.2:651MPa, A:8%, HB:336.After the test of wear and thermal fatigue, under the condition of experiment, the result of wear test show that the condition of friction is the mix of boundary friction and dry friction. The order of wear resistant:ductile iron> aluminum bronze of present work> beryllium bronze. The order of thermal fatigue resistance:beryllium bronze> aluminum bronze of present work> ductile iron. So aluminum bronze was considered as the new material for the plunger tip.In addition, the dendritic morphology of P phase was shown by increased the cooling rate and micro segregation. After the analysis of the phases, it is found that the shape of a phase is sheet or block in optical microscope, but it is needle plate in three-dimensional space in fact. What’s more, in the present work, the kⅠ particle is considered formed from liquid of alloy, instead of the early stage of phase transformation after solidification. And the precipitation of kⅡ particle contributes the refinement of a phase.