Effect of gas nitriding process on microstructure and properties of NbVTi alloyed gray cast iron

doi:10.13251/j.issn.0254-6051.2020.08.037

Abstract

Abstract: In view of the development trend of high speed and heavy load of engine, a new type of NbVTi alloyed gray cast iron cylinder liner material was gas nitrided under different temperature. The effect of gas nitriding process on microstructure and properties of NbVTi alloyed gray cast iron cylinder liner was studied by means of metallographic microscope, Vickers hardness tester and friction wear testing machine. The results show that with the increase of nitriding temperature, the nitrided depth of NbVTi alloyed gray cast iron cylinder liner is increased, and the microhardness at the depth of 100 μm and 130 μm from the surface is increased first and then decreased. After nitriding at the optimum nitriding temperature of 570 ℃, the cylinder liner size expands in the standard range of 0.010-0.055 mm, the average thickness of nitrided layer is about 140 μm, and the average hardness of the diffusion zone at the depth of 100 μm from the surface is above 500 HV0.1, which can meet the requirements of high speed and heavy load cylinder liner. After nitriding, the friction and wear performance of cylinder liner is greatly improved. With the increase of load and speed, the wear rate increases, and the wear mechanism changes from abrasive wear to adhesive wear.

Key words: NbVTi alloyed gray cast iron, nitrided layer, hardness, microstructure, wear resistance

CLC Number:

TG142.71

Meng Chao, Guo Caiping. Effect of gas nitriding process on microstructure and properties of NbVTi alloyed gray cast iron[J]. Heat Treatment of Metals, 2020, 45(8): 189-193.

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