Study On Carbide Precipitation Behavior Of Powdered High Speed Steel During Heat Treatment

In this paper,the PM23,PM60,PM60-like self-made powder high-speed steel is quenched and tempered at high temperature to detect the hardness,carbide content and particle size after heat treatment,and the effect of quenching and tempering on the carbide precipitation of the material is studied.Among them,the quenching temperature changes include 1100℃,1150℃,1180℃,and 1200℃,and the tempering temperature changes include 560℃,600℃,and 640℃.The study found that the carbides of PM23 and PM60 in the annealed state,after quenching at 1200℃,and after tempering at 1200℃+560℃ are MC type and M₆C type.As the quenching temperature increases,the hardness of the three materials first decreases,then increases and then decreases.When the quenching temperature reaches 1180℃,the hardness increases.PM23,PM60,and HK reach the highest hardness in the quenched state at 1180℃,1100℃,and 1180℃ respectively.It is 64.8HRC,69.1 HRC,67.6 HRC.After tempering,the carbide content of PM23 and HK becomes less and melts back into the martensite matrix.The quenching temperature affects the tempering temperature of the maximum secondary hardening of PM23.After tempering,the maximum hardness of the three materials is as follows:1200℃quenched+560℃tempered PM23（65.5HRC）,1150℃quenched+560℃tempered PM60（68.4HRC）,1150℃quenched+HK tempered at 560℃（69.3HRC）.After tempering,the ratio of the secondary carbide content to the total carbide content has a linear relationship with the hardness.The precipitated secondary carbides exist in both M₆C type carbides and MC type carbides.In terms of element distribution,there is a difference between the quenched state and the tempered state.The two quenched carbides can be distributed separately in a spherical carbide,and the carbide containing more V elements is wrapped around the carbide containing more W and Mo.W and Mo penetrate into the MC carbide in a permeable state,and the interface between the W and Mo-rich M₆C carbide and the MC carbide is not clear.The tempered state is different.There is a clear boundary between carbides with high V content and carbides with low V content.Although there are boundaries between M₆C-type carbides and MC-type carbides,they are clearly the boundaries between different carbide particles.After analyzing the line scan energy spectrum of the material,V and Cr have a mutually promoting relationship,and the two have an inhibiting relationship with Fe.PM23 is different from PM60 and HK in terms of element composition.PM23 without Co is significantly different from PM60 and HK containing Co.PM23 has significantly less carbide content in the tempered state,and the hardness after tempering is also lower.,Co element can promote the precipitation of carbides and increase the hardness.