Molybdenum Oxide Coatings Deposited on Plasma Nitrided Surfaces (original) (raw)
Related papers
Journal of Materials Science, 2008
Significant progress has been made in the past decade in plasma nitriding with a majority of the research work focusing on improving hardness and wear resistance of the nitrided surface through the reduction of nitriding temperature, pressure or time. Hard-solid lubricating coatings have also been extensively studied for lowering the wear rate and coefficient of friction of traditional hard coatings such as TiN by the combined effect of hardness and solid lubrication. In this study, the wear characteristics of low-temperature plasma-nitrided steel substrate performed using a Saddle-field fast atom beam source and TiN + MoS x hard-solid lubricant coating deposited by a closed-field magnetron-sputtering technique have been investigated. The thin hard layer in plasma-nitrided substrates exhibited much higher hardness and lower wear compared to the untreated substrate in pin-on-disc wear testing. In addition, the study of the wear track morphology of the nitrided samples evidenced significant reduction of deeper ploughing and plastic deformation due to higher hardness and load supporting of the nitrided layer. On the other hand, due to the incorporation of MoS 2 in TiN coating, the wear resistance and coefficient of friction were greatly improved in TiN + MoS x coating compared to pure TiN coating. In contrast to TiN coating, a relatively smoother wear track with less abrasive wear also supported the beneficial effects of adding MoS 2 in TiN coating.
Tribological properties of plasma electrolytic oxide coatings on magnesium alloys
Tribology - Materials, Surfaces & Interfaces, 2012
Plasma electrolytic oxidation (PEO) is a promising and environmentally friendly surface modification process free of Cr z6 and heavy metals. The process forms a protective and well adhered ceramic coating on valve metals such as Mg, Al and Ti. In this study, AZ91D and AM60B Mg alloys commonly used in automotive and aerospace industries were surface treated using an industrial scale PEO system in a KOH-Al 2 O 3 based alkaline electrolyte. PEO coatings of two different nominal thicknesses, i.e. 10 mm (K10) and 25 mm (K25), were obtained. The microstructure and phase composition of the PEO coatings were analysed using scanning electron microscopy and X-ray diffraction respectively. Scratch tests were carried out to determine the adhesion strength of the PEO coatings. The tribological behaviour of PEO coatings under dry sliding conditions against 100Cr6 steel ball was investigated using the ball-on-plate test configuration. Test results indicated that the PEO coatings significantly enhanced the wear resistance of Mg alloys with increasing coating thickness. For uncoated Mg plates, abrasive and adhesive wear mechanisms acted together during sliding motion, while no predominant wear mechanism was seen for PEO coated alloys.
Tribological properties of plasma nitrided and hard coated AISI 4140 steel
Wear, 2001
In the present study, samples made of AISI 4140 steel pre-treated with plasma nitriding and coated with different PVD coatings (TiN, TiAlN and ta-C) were investigated in terms of their microhardness, surface roughness, scratch adhesion and dry sliding wear resistance. Wear tests, in which duplex-treated pins were mated to hardened ball bearing steel discs, were performed with a pin-on-disc machine. To examine the influence of the nitrided zone on the performance of the coating-substrate composite, coatings were deposited on hardened as well as on plasma nitrided samples, prepared under different nitriding conditions.
Journal of Materials Engineering and Performance, 2011
The aim of this study is to investigate the effect of plasma nitriding pre-treatment (PN) on mechanical and tribological behavior of TiN coatings produced by plasma-assisted chemical vapor deposition (PACVD). The heat treatment of quench and temper was carried out on hot work AISI H11 (DIN 1.2343) steel samples. A group of samples were plasma nitrided at 500°C for 4 h in an atmosphere containing 25 vol.% nitrogen and 75 vol.% hydrogen. Then TiN layer was deposited on all of samples at 520°C temperature, 8 kHz frequency, and 33% duty cycle. The microstructural, mechanical, and tribological properties of the coatings were investigated using SEM, WDS, AFM, microhardness tester, and pin-on-disc wear test. The load of wear test was 10 N and the samples were worn against different pins, ball-bearing steel (DIN 1.3505), and cemented tungsten carbide (WC-Co). The results indicate that the difference of hardness between the samples with PN-TiNlayer and those samples with only TiN layer without PN was 450 HV and the former samples showed a significant amount of wear resistance in comparison to the latter ones.
Improvement of wear resistance of plasma-sprayed molybdenum blend coatings
Journal of Thermal Spray Technology, 2005
The wear resistance of plasma sprayed molybdenum blend coatings applicable to synchronizer rings or piston rings was investigated in this study. Four spray powders, one of which was pure molybdenum and the others blended powders of bronze and aluminum-silicon alloy powders mixed with molybdenum powders, were sprayed on a low-carbon steel substrate by atmospheric plasma spraying. Microstructural analysis of the coatings showed that the phases formed during spraying were relatively homogeneously distributed in the molybdenum matrix. The wear test results revealed that the wear rate of all the coatings increased with increasing wear load and that the blended coatings exhibited better wear resistance than the pure molybdenum coating, although the hardness was lower. In the pure molybdenum coatings, splats were readily fractured, or cracks were initiated between splats under high wear loads, thereby leading to the decrease in wear resistance. On the other hand, the molybdenum coating blended with bronze and aluminum-silicon alloy powders exhibited excellent wear resistance because hard phases such as CuAl2 and Cu9Al4 formed inside the coating.
Assessment of tribological properties of plasma nitrided 410S ferritic-martensitic stainless steels
Wear, 2019
Low Temperature Plasma Nitriding (LTPN) is a surface treatment that promotes surface hardening without harming the corrosion resistance of martensitic stainless steels. LTPN and conventional plasma nitriding (CPN) treatments were carried out to compare the influence of the obtained nitrided layers on the abrasive wear resistance of AISI 410S ferritic-martensitic stainless steel. The samples were plasma nitrided for 20 h in a gas mixture of 75% N 2 : 25% H 2 , at 250 Pa. LTPN was carried out at 400°C, obtaining a 50 µm thick expanded martensite layer. CPN done at 530°C, resulted in a 170 µm nitrided layer, with an outermost compound layer 15 µm in thick. Nanoindentation tests to assess the mechanical properties and the energy dissipation coefficient were carried out. Scratch and micro-abrasion tests were conducted to evaluate the friction coefficients, failure modes, critical loads and wear resistance. Tensile cracking was the prevalent mechanical failure mode of the nitrided layers. Micro-abrasion results showed that LTPN and CPN samples exhibited similar wear volume losses. A change in the wear volume loss rate with sliding distance was observed for the nitrided samples. A change from grooving to rolling abrasion explains the change in the wear rate.
In this study, the microstructural features, mechanical properties and dry sliding wear characteristics of NiCrBSiCFe plasma-sprayed on AISI 316 austenitic stainless steel (ASS) substrate were investigated. The coatings obtained were defect-free and metallurgically bonded to the substrate. Wear tests were carried out at 1 m/s sliding velocity under the load of 20 N for 2000 m sliding distance at various atmospheric conditions like room temperature, 150, 250 and 350 • C using a EN-8 medium carbon steel pin as a counterface material. The properties namely coating density, microhardness, coefficient of friction (CoF), wear resistance of the plasma-sprayed coating were studied. NiCrBSiCFe plasma-spray coated steel substrate showed superior wear resistance properties than the uncoated steel substrate in all the temperatures. The average wear resistance values of uncoated and NiCrBSiCFe coated material are 129 and 540 m/mm 3 , respectively. Thereby, the sliding wear resistance was improved up to four times more than that of the uncoated material. In wear test carried out at 350 • C, the coated substrates showed relatively lesser wear than in other temperatures due to the iron and chromium oxide formation, which acted as a protective layer. This was evident from X-ray diffraction studies (XRD). In addition, the shallow ploughing mode of wear reduced the severity of material removal at 350 • C. Using scanning electron microscope (SEM) pictures, the wear properties of the coated steel substrate were evaluated in terms of plastic deformation, material transfer and abrasion.
Wear performance of Nb-alloyed, pulsed plasma nitrided Mo3Si intermetallic
International Journal of Refractory Metals and Hard Materials, 2007
Several alloys produced by arc cast method were obtained, with Nb additions up to 20 at%. The samples were thermo-chemical treated with pulsed plasma nitrided for 24 h. A pin-on-disk system was employed to perform wear experiments under non-lubrication condition. After wear analysis, the treated samples in all range of Nb concentrations have shown less mass losses in comparison with samples without surface modification, until the nitrided zone is removed. Surface oxidation studies leaded to the conclusion that the increased wear resistance is due to the higher surface hardness together with the mixture of different Nb, Si and Mo oxides generated during the wear process identified by SEM and chemical analysis. The friction coefficient is of the order of 10 À3. The improved specific wear rate is of the order of 10 À6 mm 3 /N m and shows an increment of 39.9% respect to the samples with 5 at% Nb and 10 at% Nb, this results clearly show that Nb additions is beneficial for the wear resistance of the alloy.
In the present study, samples made of AISI 4140 steel, pre-treated with plasma nitriding (PN) and coated with coatings like Titanium Nitride (TiN), Titanium Carbo Nitride (TiCN), Chromium Nitride (CrN), Aluminium Titanium Nitride (AlTiN) using Physical Vapour Deposition (PVD) technique, were investigated in terms of their dry and wet sliding wear behaviour. Wear tests, were performed with a pin-on-disc machine. The results of the duplex treated samples were compared with the conventional hard chrome coated AISI 4140 steel. The results showed improved wear properties of the duplex-treated specimens compared to the hard chrome coated AISI 4140 steel. TiCN coated and nitrided 4140 steel has shown the best performance among the investigated materials. Furthermore, the compound layer formed during nitriding was found to act as an intermediate hard layer leading to superior sliding wear properties. The improved performance of the duplex treated samples can be attributed to the presence of a nitrided subsurface. ARTICLE HISTORY