The pulse plasma nitrocarburizing for 30CrMnSiA steel was conducted at 560 ℃ for 8 h in mixed gases of N2：3H2 and different flow rates of rare earths （RE） addition. Effects of rare earths （RE） addition in the ca...The pulse plasma nitrocarburizing for 30CrMnSiA steel was conducted at 560 ℃ for 8 h in mixed gases of N2：3H2 and different flow rates of rare earths （RE） addition. Effects of rare earths （RE） addition in the carrier gas on the surface morphology, phase structure and mechanical properties of the nitrocarburized layer were characterized by optical microscopy （OM）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, microhardness testing and wear testing, respectively. The results showed that the surface phase structures changed from dual phases ε-Fe2.3N（C） and γ′-Fe4N（C） to phase Fe3C and incipient nitrides, and the nitrocarburized surface hardness value decreased slightly from 756 to 681 HV0.1 with the RE addition increasing in the cartier gas, and the corresponding morphology of the nitrocarburized surface was granular nitride group （diameter 0.8-1.5 μm） and compact-fine Fe3C stick and patch （mean size 100-300 nm）, respectively. The wear resistance of the experimental steel could be improved remarkably by plasma RE nitrocarburizing. The nitrocarburized layer with Fe3C phase formed in the mixed gases of N2：3H2 and flow rate of 0.5 L/min RE addition showed the lowest friction coefficient and the narrowest wear track.展开更多
The probabilistic control volume method has great prospects in correlating the effects of specimen size,notch and loading type on fatigue life or fatigue strength.In this work,the effects of notch size and loading typ...The probabilistic control volume method has great prospects in correlating the effects of specimen size,notch and loading type on fatigue life or fatigue strength.In this work,the effects of notch size and loading type on fatigue life are investigated by using the probabilistic control volume method.Rotating bending and axial loading fatigue te«t«are at first performed on the hourglass specimen,circumferential V-notch specimen and V-notch plate specimen of 30CrMnSiA steel.Experimental results indicate that the notch reduces the fatigue strength of specimens in terms of nominal stress amplitude while in terms of local stress amplitude,the notch specimen could endure higher fatigue strength.Then,the probabilistic control volume method is used to evaluate the effects of notch size and loading type on fatigue life.It is shown that the probabilistic control volume method correlates well the effects of notch size and loading type on fatigue life,even for the local stress of the notch root exceeding the yield stress of the material.展开更多
基金Project supported by National Natural Science Foundation of China(51071061)NSAF Foundation of National Natural Science Foundation of China and China Academy of Engineering Physics (11176011)
文摘The pulse plasma nitrocarburizing for 30CrMnSiA steel was conducted at 560 ℃ for 8 h in mixed gases of N2：3H2 and different flow rates of rare earths （RE） addition. Effects of rare earths （RE） addition in the carrier gas on the surface morphology, phase structure and mechanical properties of the nitrocarburized layer were characterized by optical microscopy （OM）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, microhardness testing and wear testing, respectively. The results showed that the surface phase structures changed from dual phases ε-Fe2.3N（C） and γ′-Fe4N（C） to phase Fe3C and incipient nitrides, and the nitrocarburized surface hardness value decreased slightly from 756 to 681 HV0.1 with the RE addition increasing in the cartier gas, and the corresponding morphology of the nitrocarburized surface was granular nitride group （diameter 0.8-1.5 μm） and compact-fine Fe3C stick and patch （mean size 100-300 nm）, respectively. The wear resistance of the experimental steel could be improved remarkably by plasma RE nitrocarburizing. The nitrocarburized layer with Fe3C phase formed in the mixed gases of N2：3H2 and flow rate of 0.5 L/min RE addition showed the lowest friction coefficient and the narrowest wear track.
基金The authors would like to acknowledge the support from the Innovation Program(2370990000-00170004)the National Natural Science Foundation of China(91860112)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB22020200).
文摘The probabilistic control volume method has great prospects in correlating the effects of specimen size,notch and loading type on fatigue life or fatigue strength.In this work,the effects of notch size and loading type on fatigue life are investigated by using the probabilistic control volume method.Rotating bending and axial loading fatigue te«t«are at first performed on the hourglass specimen,circumferential V-notch specimen and V-notch plate specimen of 30CrMnSiA steel.Experimental results indicate that the notch reduces the fatigue strength of specimens in terms of nominal stress amplitude while in terms of local stress amplitude,the notch specimen could endure higher fatigue strength.Then,the probabilistic control volume method is used to evaluate the effects of notch size and loading type on fatigue life.It is shown that the probabilistic control volume method correlates well the effects of notch size and loading type on fatigue life,even for the local stress of the notch root exceeding the yield stress of the material.
