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Study on the Surface Nanocrystallization and Pulse Plasma Re Nitriding of Steel 17-4PH

Author: ChenHongTao
Tutor: ZuoMuFu
School: Harbin Institute of Technology
Course: Materials Science
Keywords: 17-4PH steel Surface nanocrystallization Peening Laser surface hardening Pulsed plasma nitriding of rare earth
CLC: TG156.82
Type: Master's thesis
Year: 2008
Downloads: 44
Quote: 1
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Abstract


17-4PH steel surface nano technology, pulse plasma nitriding process . Peening , laser surface hardening and shot peening and laser surface quenching composite processing technology , 17-4PH surface nano technology . The test results show that the laser surface hardening can be obtained at the surface of the material layer the submicron grain , the composite laser peening and shot peening process nano material surface can be achieved . By the presence or absence of shot peening surface the plasma the rare earth nitriding test obtained nitriding investigated the effect of nitriding material surface hardness and shot peening . Shot peening under different process test results show that the choice of a larger diameter pellets , using a larger pressure , appropriate extend peening time , can further refine the crystal grains of the surface layer , the surface of the large thickness of the nano . XRD results showed that shot peening can achieve 17-4PH steel surface nanocrystallization within the outermost layer of about 20μm average grain size of 89 nm . TEM observations from the surface 75μm at sub-grain size less than 100 nm . Laser surface hardening studies have shown that the lower scan speed , and power can be obtained at the surface of the material thickness greater quenching layer ; choice of appropriate power , increase the scan speed can be increased quenching layer of grain refinement ; direct laser surface hardening material surface 365μm within the size to about 1-2μm grain , two laser quenching can be obtained in the material surface 480μm within the submicron grain ; combination of shot peening and laser surface hardening process characteristics , peening and laser surface hardening the composite processing technology, the surface of the material to obtain a 230μm -thick transition from nanometers to grains of submicron gradient . 17-4PH at 460 ° C pulsed plasma nitriding of rare earth nitriding 12h can be obtained in the surface layer of the nitrided layer of 90μm , the surface hardness of approximately HV1200 . The peened surface having a reminder infiltration role early in the rare earth nitriding with infiltration nitrogen time prolonged , reminder infiltration weakened late , nitriding hindered nitriding . Compared with no shot peening , shot peening nitriding significantly improve the micro-hardness of the nitrided surface layer , up to HV1350 .

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Heat treatment > Heat treatment process > Chemical treatment > Nitriding, cyaniding, carbonitriding
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