Process Research Of Surface Treatment And Ti Alloying On40Cr Steel By HCPEB

As a core manufacturing part, gears are widely employed in high-end manufacturinglike automobile, nuclear power, wind power and aerospace. Better stability, greaterreliability and longer working life are needed for high-end gears compared with traditionalgears, which also are required for better bearing performance. With the rapid developmentof surface engineering technology, it has been an important research area to use varioussurface modification technologies to improve the carrying capacity of gear.This paper is based on one part of Chongqing Natural Science Fund project “TheGear Surface Alloying Process and Performance Study by Electron Beam”(No.cstc2012jjB70002). Gear material is the main research object in this project. The paperfocuses on the surface treatment process of HCPEB irradiation in combination with plasmanitriding. Meanwhile, the process of HCPEB irradiation in combination with physicalvapor deposition (PVD) by which conducting surface plating Ti alloying and improvingTiN coating through HCPEB were studied too. Combined with several kinds of surfaceengineering technologies, the effects of gear surface modification by HCPEB had beenexplored, which would provide some beneficial experience to improve gear surfaceproperties by HCPEB composite surface treatment process.The following results were obtained through the research:(1) After HCPEB treatment,"melting pit" morphology was showed on the surface of40Cr, and the number of "melting pit" presented waves status with the pulse numberincreases. Meanwhile, the maximum surface hardness value was623HV0.05which wasobtained under the parameter30KV-5pulses. The surface formed "melting layer", whichhad the highest hardness at the surface and declined sharply from0~20μm under thesurface with the lowest hardness reached at20μm in depth.(2) Under the process of40Cr+HCPEB+N, the surface morphology of40Cr was thesame as that by40Cr+HCPEB. It reached a maximum value of645HV0.05when theHCPEB parameter was24KV-5pulses. After the electron beam irradiation, the existence ofthe “fused” layer in the cross section organization hindered the diffusion of nitrogen. Afterelectron beam irradiation on the surface of the ion nitriding40Cr, both of the cross-sectionhardness and the surface hardness were lower than ion desalting state. (3) Under the process of40Cr+N+HCPEB, with the increase of pulse, the quantity of"melting pit" presented a waving and downward trend which was similar with the processof40Cr+HCPEB. At the same time, the maximum surface hardness value achieved at795HV0.05when the HCPEB parameter was30KV-45pulses. And the surface organizationwas constituted by fused layer and heat affected layer. Gradient descent trend was showedin the cross-section micro-hardness which was from the surface to the heart. But it wasfalling gently when the depth within the scope of the40~120um.(4) According to the surface hardness arrangement from high to low:40Cr+N+HCPEB>40Cr+N>40Cr+HCPEB+N>40Cr+HCPEB>40Cr. And the surfacehardness of40Cr+N+HCPEB was2.7times as that of40Cr.(5) Using magnetron sputtering to plat about2um Ti film on the surface of40Cr, Ticould be spread into40Cr surface under the HCPEB parameter was15~27KV-5pulses;When the HCPEB parameter was18KV-5pulses, Ti could be spread into the40Cr matrix.Using multi-arc-ion-plating to plat about2um TiN film on the surface of40Cr, it would notbe obviously damaged under the HCPEB parameter was lower than9KV and lower than30pulses, and it would still be golden yellow. Moreover, a new phase was created underthe HCPEB parameter was9~15KV-30pulses. When the HCPEB parameter was9KV-30pulses, the binding force of TiN film and40Cr was16.75N in maximum whichwas6.15N higher than no HCPEB treatment. Therefor,9KV-30pulses was the mostoptimal parameter.