Tribological Characteristics of Nitrogen (N+) Implanted Iron

The effect of implantation of nitrogen ions (1.5 MeV) on the friction and wear characteristics of pure iron sliding against M-50 steel (unimplanted) was studied in a pin-on-disk sliding friction apparatus. Test conditions included room temperature (～25°C), a dry air atmosphere, a load of ½ kg (4.9 N), sliding velocities of 0.043 to 0.078 m/s (～15 to 25 rpm), a pure hydrocarbon lubricant (n-hexadecane), or a USP mineral oil and nitrogen ion implantation doses of 5 × 10¹⁵ and 5 × 10¹⁷ ions/cm².

No differences in wear rates were observed in the low-dose (5 × 10¹⁵ ions/cm²) experiments. In the high-dose experiments (5 × 10¹⁷ ions/cm²), small reductions in initial (～40 percent) and steady-state (～20 percent) wear rates were observed for nitrogen-implanted iron riders as compared with unimplanted controls. No differences in average friction coefficients were noted for either dose.

Auger electron spectroscopy combined with argon ion bombardment revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 6 atomic percent at a depth of 8 × 10^?7 m (0.8 μm). Similar analysis within the wear scar (～2.0 × 10^?5 m subsurface) of an implanted rider after 20 μm of wear yielded only background nitrogen concentration. No inward migration of nitrogen ions was observed.     

Investigation on the tribology of Zr ion implanted tool steel

AISI D3 tool steel was ion implanted with zirconium and the improvement in surface tribological properties investigated. The Zr ion implantation was done using a metal vapor vacuum arc (Mevva) broad-beam ion source, with a mean ion energy of 130 keV and at doses of 3.6×10¹⁶, 5×10¹⁶ and 1×10¹⁷ ions/cm². Wear, friction and hardness of the implanted samples were measured and compared to the performance of unimplanted steel. The wear resistance was increased by about a factor of two, the friction remained about the same or was possibly increased by a small amount and the near-surface hardness was improved by a factor of five or more by the ion implantation. We also investigated the effect on the Zr implantation profile of the multi-component energy distribution of the ion beam.     

GCr15钢等离子体源离子注入表面改性

用等离子体源离子注入技术对GCr15钢进行了氮离子注入,对注入层的成分进行了俄歇剖面分析,对注入层的显微硬度和摩擦性能进行了测试,对摩擦磨损表面进行了扫描电镜分析,研究结果表明;注入层的硬度和耐磨性均获得了明显的提高。     

Tempering temperature effects on abrasive wear of mottled cast iron

The effects of different tempering temperatures (300–600 °C) on abrasive wear resistance of mottled cast iron were studied. Abrasive wear tests were carried out using the rubber-wheel test on quartz sand and the pin test on Al₂O₃ abrasive cloths. The retained austenite content of the matrix was determined by X-ray diffraction. The wear surface of the specimens was examined by scanning electron microscopy for identifying the wear micromechanism. Bulk hardness and matrix hardness before and after the tests were measured. The results showed that in the two-body (pin-on-disc test) system, the main wear mechanism was microcutting and high matrix hardening was presented. The wear rates presented higher correlation with the retained austenite than with the bulk and matrix hardness. In the three-body system (sand–rubber wheel), the wear surfaces presented indentations due to abrasive rolling. The wear rates had better correlation with both the bulk and matrix hardness (before and after the wear test) than with the retained austenite content. There are two groups of results, high and low wear rates corresponding to each tribosystem, two-body abrasive wear and three-body abrasive wear, respectively.     

激光强化参数对40Cr钢表面组织及摩擦性能影响的研究

采用CO2横流式激光器对40Cr材料进行表面强化处理研究;使用S-360型扫描电镜观察激光硬化区金相组织及成分并观察金属表面磨损形貌;采用CHX-1超显微硬度计测量激光强化区断面的显微硬度;然后在MPX-2000盘销式摩擦磨损实验机上进行干摩擦和油润滑实验。结果表明:激光参数对表面硬度和硬化层深度有很大影响,较大的功率可使奥氏体转变充分而获得更多的马氏体,激光扫描速度越快,功率越大,显微硬度越高,硬化层越深;少量针状马氏体组织化引起表层强化,经激光硬化的表面其耐磨性可大大提高;40Cr在干摩擦条件下的平均磨损量是润滑时的5倍,40Cr和20MnSiV的磨损主要以磨粒磨损为主,同时也有粘着磨损。     

Research on the fretting wear behavior of silicon wafers before and after carbon ions implantation

Carbon ions with different doses of 2×10¹⁵ and 2×10¹⁶ ions/cm² were implanted into single crystal silicon wafers under an energy level of 80 keV. The nanohardness and elastic modulus of silicon wafers were studied on the nano-mechanical testing system. The fretting wear tests were performed on the UMT-2 Micro-tribometer to evaluate the fretting wear resistance of C⁺ implanted silicon wafer and to investigate its micro-tribological properties. The results demonstrate that the nanohardness and elastic modulus of silicon wafer with dose of 2×10¹⁵ ions/cm² decreased and those of 2×10¹⁶ ions/cm² changed little. Implanted silicon wafer with dose of 2×10¹⁶ ions/cm² had much lower coefficient of friction and wear volume under low loads, which suggests a significant effect of friction-reducing and anti-wear. The results also indicate that abrasive wear was the main wear mechanism for both virgin silicon and C⁺ implanted silicon with dose of 2×10¹⁵ ions/cm². However, adhesive wear played a significant role in the wear mechanism of the C⁺ implanted silicon with dose of 2×10¹⁶ ions/cm² under the low loads, while the abrasive wear dominated the wear mechanism under high loads.     

An investigation of the wear of abrasive grains by rubbing on diamond disks

In earlier wear studies¹ single abrasive grains were rubbed against the surfaces of metal disks under light loads. These studies have now been extended to include an examination of wear behaviour when using diamond-impregnated surfaces at lower sliding speeds and when using more accurately controlled test conditions. These wear tests provided values of wear resistance in the absence of chemical effects (i.e. at sufficiently low surface temperatures). The results are in excellent agreement with the conventional wear theory pertaining to lightly loaded sliders. The wear volumes are, however, two orders of magnitude greater than those obtained when rubbing tough grains against steel disks and three orders of magnitude greater than the results obtained when rubbing friable grains against similar metallic surfaces.     

Effect of composition and microstructure on slurry abrasion response of hardfaced martensitic stainless steel

Hardfaced martensitic stainless steel alloy was deposited on mild steel substrate by flux cored arc welding method. The slurry abrasion studies of weld-deposited hardfaced steel were performed using slurry abrasion test rig with 250–300 μm silica sand particles. The effect of weld compositional gradation on the abrasive wear resistance of hardfaced stainless steel at a distance of 0.6, 1.2, 2.4, 3.0 and 3.6 mm from the top surface was studied. The observed abrasion rates were rationalized in terms of mass loss, hardness and distance from the top surface i.e. diluted surfaces beneath the top surface. The abrasive wear mass loss increased with increasing distance beneath the top surface, which was attributed to the coarsening and morphology change in martensite phase. The results of the present work indicated change in morphology of martensite with increase in the distance beneath the top surface. The operating abrasive wear mechanisms involved ploughing, microcutting and indentation.     

Improved wear resistance of ultra-high molecular weight polyethylene by plasma immersion ion implantation

Surface modification of ultra-high molecular weight polyethylene (UHMWPE) has been explored using the novel non-line-of-slight plasma immersion ion implantation (PIII) with nitrogen. The modified surfaces were characterised by SEM and a Nano Test 600 testing machine. The tribological behaviour of PIII treated UHMWPE sliding against AISI 316L stainless steel counterfaces was evaluated using a pin-on-disc tribometer under water lubricated conditions. The experimental results show that PIII is a very promising surface engineering technique to improve such surface mechanical properties as surface hardness and elastic modulus of UHMWPE. As a result, the wear resistance of UHMWPE was significantly enhanced by a factor of three following PIII treatment, as compared with untreated material. It was found that the significantly improved wear resistance of PIII treated UHMWPE can be mainly attributed to ion bombardment induced cross-linking, and thus surface hardening.     

Effect of high-speed thermal treatment followed by ion-beam nitriding on physicomechanical properties of steel 40X

The effect of high-speed thermal treatment followed by ion-beam nitriding on the structure and physicomechanical properties of structural steel 40X is studied. The phase composition and structure of the steel and the modified layer after high-speed hardening and nitriding are determined. The effect of nitrogen ion implantation on the tribological behavior and impact strength of steel 40X is considered. The wear resistance of nitrogen-modified steel 40X increases approximately twofold compared to its initial state and damage work under applied load to the hardened surface increases by 40–50 J/cm².     

Ion implantation and surface modification in tribology

Ion implantation is a vacuum process by which virtually any element can be injected into the surface regions of a solid target. Current interest in materials technology and recent developments in ion implantation machines have resulted in ion-induced surface property changes in a variety of different fields including tribology. Large changes in friction coefficient (up to ± 60%) have been recorded on steel surfaces implanted with such ions as Pb⁺ and Sn⁺. Implantation of boron, nitrogen and molybdenum reduces wear by more than a factor of 10, from measurements with a pin-and-disc machine. An outline is given of the scope and application of ion implantation and the results evaluated in the context of the testing methods used. Examples are given of some present and future applications of ion implantation to tribology.     

爆炸硬化处理对高锰钢冲击磨损性能影响的研究

对Mn13Cr2高锰钢进行了爆炸硬化处理。并分别以玻璃砂、鹅卵石为磨料，在MLD．10动载磨料磨损试验机上对比研究了爆炸前、后Mn13Cr2高锰钢的冲击磨损性能。实验结果表明：在低硬度磨料（玻璃砂）冲击磨损时，爆炸硬化使高锰钢的冲击耐磨性提高20％-40％。在高硬度磨料（鹅卵石）冲击磨损时，在冲击功小于1．7J的条件下，爆炸硬化使高锰钢的冲击耐磨性提高30—50％。在冲击功大予1．7J的条件下，爆炸硬化则使高锰钢的冲击耐磨性降低。爆炸硬化使高锰钢表层硬化和冲击韧性降低是冲击耐磨性发生变化的主要原因。在冲击磨损条件下，爆炸硬化前、后高锰钢磨损面均出现磨料嵌入物及犁沟、凿削坑和剥落坑等形貌特征。爆炸硬化高锰钢适用予低硬度磨料的冲击磨损及高硬度磨料的低冲击功冲击磨损的工况条件。     

Adhesive and abrasive wear behaviour of TiC alloyed,sintered, austenitic stainless steels

Abstract

This study examines abrasive and adhesive wear behaviour of austenitic stainless steel and its TiC alloyed composite produced through powder metallurgy technique. Abrasive wear tests have been carried out using a pin on disc wear tester under loads of 10, 20 and 30 N. For adhesive wear tests, a block on ring wear tester has been used under loads of 20, 40, 60 and 80 N. A possible correlation between the hardness, microstructure and wear behaviour of the samples has been investigated. The abrasive wear tests have revealed that the highest rate of mass loss occurred in the austenitic matrix stainless steel sample; also, mass losses decreased with an increased rate of reinforcing material in the composite. In adhesive wear tests, interparticle spacing developed from severe wear and extreme plastic deformation under heavy loads; however, at low loads, oxidation type wear was shown to be dominant.     

Abrasive wear behaviour of sintered composite austenitic stainless steels having γ-Fe and M23C6 phases

Abstract

Using powder metallurgy, composites of austenitic stainless steel were produced along with unreinforced stainless steel mixed with titanium, cobalt and molybdenum particles. Wear resistance of the materials was measured by a two body pin on disc wear tester. SiC abrasive papers of 80 and 220 mesh sizes were used as abrasive media. Wear tests were performed under loads of 10, 20 and 30 N at room temperature. The abrasive wear measurements showed that the softer, unreinforced austenitic stainless steel exhibited higher mass loss than the composites. Furthermore, the abrasive wear resistance of the reinforced austenitic stainless steel composites increased with increasing FeTi, FeMo, or Co volume content. In addition, the wear rate against the 80 grade SiC abrasive paper increased more than against the 220 grade SiC abrasive paper.     

Effect of Sintering Temperature and Atmosphere on Nonlubricated Sliding Wear of Nano-Yttria-Dispersed and Yttria-Free Duplex and Ferritic Stainless Steel Fabricated by Powder Metallurgy

The nonlubricated sliding wear behavior of nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel against a diamond tip was studied. The stainless steel samples were fabricated by a conventional powder metallurgy route in which nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel powders were cold compacted and then conventionally sintered at either 1000, 1200, or 1400°C in an argon atmosphere. For comparison, another set of samples was sintered at 1000°C in a nitrogen atmosphere. The wear behavior of sintered stainless steel samples against a diamond indenter was investigated using a pin-on-disc apparatus at 10 and 20 N loads and at a constant speed of 0.0041 m/s. It is proposed that yttria-dispersed stainless steels showed higher wear resistance compared to yttria-free stainless steel due to their improved hardness and density. Stainless steel sintered in a nitrogen atmosphere exhibited better wear resistance than those sintered in an argon atmosphere due to the formation of hard and brittle Cr₂N. The wear mechanisms of stainless steels against diamond were found to be mainly abrasive and oxidative. Semiquantitative analysis of the worn surfaces and wear debris confirmed the occurrence of oxidation processes during wear.     

Tribological properties of nitrogen ion implanted steel

Nitrogen ions (N⁺) with three different doses were implanted on the AISI 304 LN steel samples under high vacuum at room temperature. Dose dependent morphological and structural changes were observed in the specimen. Structural changes were triggered by formation of nitrides; irradiation induced surface segregation of carbon and deposition of amorphous carbon (a-C) by the cracking of hydrocarbons during implantation from oil diffusion pump. Morphological and structural changes were found to influence nano-mechanical and tribological properties of ion implanted surfaces. The nano-indentation hardness was found to increase to 10.26 GPa with highest N⁺ ion dose due to formation of surface nitrides and amorphous carbon. Frictional force was found to decrease with increase in N⁺ ion dose and a minimum value of 0.078 N was obtained at higher dose presumably due to the formation of amorphous graphite like phase. In addition, amorphous diamond like carbon on the implanted surface can be contributing facts for high hardness. At higher dose, both deformation induced damage and wear rate (2.4 × 10^?7 mm³/Nm) were found to be minimum.     

Modification of Tribological Properties of Silicon by Boron Ion Implantation

Friction and wear properties of silicon used in the fabrication of microelectromechanical systems (MEMS) are important for their long-term reliability. In the present study, the authors have implanted single-crystal and polycrystalline silicon wafers with boron ions to improve their mechanical and tribological properties. The authors have studied the effects of ion implantation on the crystallinity, microstructure, nanohardness, and friction and wear properties and have found that silicon remains crystalline after ion bombardment at doses up to 2 × 10¹⁷ ions.cm^?2 but with a large amount of defects. The ion bombardment modifies elastic/plastic deformation characteristics and crack nucleation that occurs during indentation. There is a minor increase, ? 10-15 percent, in the nanohardness as a result of boron-ion implantation. Ion bombarded single-crystal silicon exhibits very low friction (0.05) and low wear factor (10^?6 mm³·N^?1m^?1) while slid against a 52100 steel ball. The coefficient of friction of bombarded silicon in dry air and dry nitrogen is even lower.     

Ductility and the abrasive wear resistance of hot work die steels

Two-body abrasive resistance has been determined as a function of tempering temperature for a conventional hot work die steel and two experimental hot work die steels. After tempering in the secondary hardening range both experimental steels exhibit abrasive wear resistance comparable with or superior to that of the conventional die steel. In addition, the abrasive wear behavior of the three steels has been assessed using an approach suggested by one of the authors which emphasizes the role of ductility in determining abrasive wear resistance. As suggested by that approach, the product of the wear ratio and the bulk hardness tends to decrease with increasing tensile strain to fracture.     

Formation of wear debris by the abrasion of ductile metals

Decohesion of wear debris by abrasive particles was studied using polycrystalline pure metals and alloys. Wear debris were formed by steel riders with attack angles of 30°, 60° and 90° and also in the pin-on-disk test on commercial abrasive paper. Microstructural changes due to abrasion were investigated by transmission electron microscopy and X-ray diffraction examination of wear debris and worn surfaces. Simple models for the interaction between abrasive particles and material surfaces used to estimate friction and wear provided a better quantitative understanding of the influence of microstructural factors such as hardness, work hardening, crystal structure, anisotropy and phase transformation.     

Subsurface characteristics of an abraded low carbon steel

Ductile metals commonly exhibit plastic deformation at and near the worn surface and their flow behaviour at large strains has a clear effect on wear resistance. In this study, the characteristics of the near-surface region of a ferritic-pearlitic steel (0.2% C, 1.2% Mn), subjected to abrasive wear tests, were examined. Wear tests were performed under different loads by rubbing the specimens on sliding 60 mesh Al₂O₃ abrasive band. The metallographic technique used to determine the magnitude of plastic deformation was based on measurement of the displacements of pearlite bands. The hardness of the plastic deformation zone was determined by performing ultramicrohardness tests along ferrite bands with a Vickers indenter. Microscopic examinations of the near-surface regions revealed the wear mechanism to be ploughing and the deformation mechanism to be cross-slip. It was observed that plastic strain (more than 6) occurred on the abraded surface, and increased the hardness to about 1.5 times the original value. The strain and hardness gradient extended to a larger depth into the bulk with increasing wear test load. It is concluded that the wear resistance of the investigated steel increases by work hardening of the near-surface region which is required to consume high energy for abrasion, during sliding. Ultramicrohardness measurements performed on worn specimens revealed high hardness, as the indent size decreased. The indentation size-hardness relation was explained by a dislocation model incorporating geometrically necessary dislocations due to the presence of strain gradients in the deformation region around the indent.