Research Of Powder Forging Fe-C-Cu-Cr Alloy On Microstructure And High Temperature Properties

The effects of element content about chromium and carbon,adding modes on the microstructures and properties of Fe-C-Cu-Cr alloy are studied.Taking Fe-2Cu-0.5C-5Cr as the matrix,the effects of the ball milling process and the adding of yttrium oxide on microstructures and properties are studied.The influence of Cr and C content on the properties of Fe-C-Cu-Cr alloys shows that the density of the alloy increases greatly after forged.The chromium has a greater influence on the density than the carbon.The micorstructures become from ferrite and pearlite to carbide,Cr-rich area and Cr-poor area with the adding of chromium.The sample of Fe-2Cu-0.8C-10Cr has the highest hardness(68.6 HRA).The high temperature tensile strength of Fe-2Cu-0.5C-5Cr is the highest,reaching to 378 MPa,and the elongation decreases with the chromium content increases.The friction coefficient of alloy increases and then decreases to stabilizes with the increase of temperature.The high temperature friction coefficient and wear rate of the sample with 10 wt.%Cr is the lowest(0.195 and 4.21×10^-5mm³·N^-1·m^-1).The wear mode are mainly oxidative wear and abrasive wear.The research on the effect of adding modes on the properties of Fe-C-Cu-Cr alloy shows that the properties of the sample formed by adding four kinds of powders with different chromium content(3 wt.%,18.7 wt.%,78 wt.%and 99%wt.%)are in big difference.The sample formed by adding Fe-Cr(3 wt.%)and Fe-Cr(18.7 wt.%)powder has a lot of martensite,while the samples formed by adding Fe-Cr(78 wt.%)and Fe-Cr(99 wt.%)consist of a large amount of ferrite and pearlite and a small amount of martensite.The hardness,high temperature tensile strength and high temperature friction resistance of the Fe-Cr(3 wt.%)and Fe-Cr(18.7wt.%)samples are better than others.So the two powder adding methods are in better alloying,the sample of Fe-2Cu-0.5C-5Cr is fabricated by adding those two powders according to mass ratios.Compared with Fe-2Cu-0.5C-5Cr(78 wt.%)in previous chapter,the Fe-2Cu-0.5C-5Cr(3 wt.%and 18.7 wt.%)is better in terms of density,hardness,tensile strength and high-temperature friction resistance.The research on effect on ball milling process and Y₂O₃ on the properties of Fe-C-Cu-Cr alloy shows that the powder deformed by ball milling and become finer,which is not conducive to pressing density.Ball milling can promote the diffusion of chromium,and reduce the Cr-rich area.Carbides are formed with a network structure in the Cr-rich areas during ball milling,which lead to the less improvement of high temperature tensile strength.The nano Y₂O₃ powder can inhibit the formation of carbides and the movement of dislocations at high-temperature,which can improve the tensile strength of the sample greatly,up to 576 MPa.The wear modes of the three samples in the high temperature friction are oxidation wear and abrasive wear.The friction coefficient and wear rate of the Fe-2Cu-0.5C-5Cr-0.5Y₂O₃ sample after ball milling is the lowest(0.105 and 2.34×10^-5mm³·N^-1·m^-1).The sample of Fe-2Cu-0.5C-5Cr after ball milling has the least abrasive grains and the shallowest plough marks.