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Tribological Characteristics of 304L Stainless Steel and As-deposited Nickel-based Surfacing

Author: WeiYanHui
Tutor: ChenGuoQing
School: Dalian University of Technology
Course: Materials Processing Engineering
Keywords: 304L Ni50 Plasma welding Martensitic transformation Wear mechanism
CLC: O313.5
Type: Master's thesis
Year: 2011
Downloads: 90
Quote: 1
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Abstract

The friction and wear mechanisms in order to explore the nuclear pump with stainless steel to improve its wear resistance and tribological properties of 304L stainless steel and its surface Ni50 alloy plasma surfacing layer. Using X-ray diffraction and metallographic observation, analysis of the microstructure evolution of 304L stainless steel and Ni50 alloy plasma surfacing layer friction and wear processes. MMS-2A type friction and wear testing machine under different loads friction coefficient changes with time. Study the wear process different loads and different times of the amount of wear and wear rate variation; JSM-5600LV scanning electron microscope, the observed material surface wear morphology, to investigate the friction and wear mechanisms. The results show that the 304L stainless steel substrate friction and wear, the worn surface of martensitic transformation. The amount of wear of the material over time and the increase of the load increases. Due to the phase transformation strengthening and debris is oxidized to form a lubricating thin layer, the wear rate of the sample is reduced with increasing wear time; small difference, the amount of wear and the wear rate and the 30 N load of 70 N, 120 N under a heavy load, the material is badly worn, the amount of wear and the wear rate is much higher than the 70 N and 30 of N. The initial stage of the experiment, the wear mechanism is the same under different loads, the wear mechanism is abrasive wear and adhesive wear. As the experiment progresses, under different experimental load, wear mechanism is different, even if the same kind of experiments under a load, the wear mechanism is also changed over time. 30 N load, the wear mechanism is abrasive wear, adhesive wear and oxidation wear. 70 N load, the experimental time of 30 min and 90 min, the wear mechanism was adhesive wear and oxidation wear; 180 min, the wear surface pitting. Load of 120 N, the experimental time for 30 min, the wear mechanism is adhesive wear; 90 min, the wear mechanism is abrasive wear and adhesive wear; 180 min, the wear surface fatigue wear. Studies have shown that the microstructure and tribological properties of 304L stainless steel surface Ni50 alloy plasma surfacing layer, surfacing layer can be divided into four regions: the heat-affected zone, combining zone, central melt zone and the top of the melting zone. Surfacing layer of Ni-base γ (Fe, Ni) and CrB, Cr23C6 etc.. Wear after surfacing layer did not occur to the austenite to martensite transformation has greatly improved its wear resistance than 304L stainless steel substrate. The main wear mechanism of the surfacing layer of material is varied with time and the test load of different stage of the start of the experiment, low-load conditions, the main wear mechanism is abrasive wear, while the high load is adhesive wear. Experimental time is longer, the wear mechanism in the low load primarily for adhesion and oxidation wear; higher loads of fatigue and oxidation wear.

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