ВЛИЯНИЕ ОТЖИГА ВАКУУМНО-ДУГОВЫХ ПОКРЫТИЙ TiN НА ИХ НАГРУЗКУ ОТСЛАИВАНИЯ И СОПРОТИВЛЕНИЕ ФРЕТТИНГ-ИЗНАШИВАНИЮ

Fretting wear characteristics of Molybdenum disulphide (MoS2)-bonded solid lubricant coating on structural steel, AISI 4340, when fretted against hardened-tempered bearing steel, AISI 52100 are reported in this paper. Fretting wear tests were conducted at different normal loads and at constant slip amplitude of 60 μm. Coefficient of friction under fretting conditions and wear resistance were measured. The MoS2-bonded solid lubricant offers improved fretting wear resistance against bearing steels. Substrate hardness has influenced the coating behaviour at high loads. The fretting wear resistance also depends upon the normal load and the nature of contact, stick slip, or gross slip.

Influence of silicon infiltration on the wear and oxidation resistance of hot-pressed B4C/C(graphite) composites

The effect of annealing at 350–500 °C on the structural-phase state, nanohardness, elastic modulus and critical peel load Lc of vacuum-arc TiN coatings deposited on a substrate made of pre-annealed 90CrSi steel was investigated. It has been established that the coating contains TiN and Ti phases. The nanohardness of the coating is 29 GPa, and the elastic modulus is 485 GPa. It was concluded that the increased values of the nanohardness and coating elastic modulus are associated with the presence of a large number of crystal lattice defects in it. It is shown that as the annealing temperature of the coating increases from 350 to 500 °C, the values of the nanohardness and elastic modulus of TiN coatings decrease, while an increase in the crystal lattice parameter, as well as a decrease in the dislocation density and TiN dispersion are recorded. An increase in the crystal lattice parameter of TiN during annealing of the coating is associated with the formation of vacancy complexes in it. It was found that as a result of annealing TiN coatings, the peeling load increases from 12.8 to 21.1 N. It was concluded that the increase in the peeling load of the coating during annealing is associated with the formation of an oxide film, which prevents the nucleation (generation) of dislocations during the introduction and movement of the indenter in the coating and, thus, slows down the formation of microcracks at the boundary of the coating and the substrate.

Influence of glow plasma Co-based alloying layer on sliding wear and fretting wear resistance of titanium alloy

High hardness and good wear resistance have been revealed for the high-entropy alloy (HEA) system AlCoCrFeNiTi, confirming the potential for surface protection applications. Detailed studies to investigate the microstructure and phase formation have been carried out using different production routes. Powder metallurgical technologies allow for much higher flexibility in the customisation of materials compared to casting processes. Particularly, spark plasma sintering (SPS) enables the fast processing of the feedstock, the suppression of grain coarsening and the production of samples with a low porosity. Furthermore, solid lubricants can be incorporated for the improvement of wear resistance and the reduction of the coefficient of friction (COF). This study focuses on the production of AlCoCrFeNiTi composites comprising solid lubricants. Bulk materials with a MoS2 content of up to 15 wt % were produced. The wear resistance and COF were investigated in detail under sliding wear conditions in ball-on-disk tests at room temperature and elevated temperature. At least 10 wt % of MoS2 was required to improve the wear behaviour in both test conditions. Furthermore, the effects of the production route and the content of solid lubricant on microstructure formation and phase composition were investigated. Two major body-centred cubic (bcc) phases were detected in accordance with the feedstock. The formation of additional phases indicated the decomposition of MoS2.

Purpose: In this paper, laser alloying with boron and solid lubricants was used in order to produce the self-lubricating layer on 100CrMnSi6-4 bearing steel. The influence of CaF2 and BaF2 on microstructure, hardness, chemical and phase composition as well as wear resistance of the layers was studied. Design/methodology/approach: The two-step process was used during laser alloying. First, the surface of the specimen was coated by a paste with alloying material. The alloying material consisted of the mixture of amorphous boron and self-lubricating additions (CaF2 and BaF2). Next, the surface was re-melted by a laser beam using TRUMPF TLF 2600 Turbo CO2 laser. The laser beam power 1.43 kW was used for laser alloying. The layer was characterized using X-ray diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, microhardness tester. The dry sliding wear behaviour of the layer was investigated using the Amsler type wear test. Findings: The tribofilm, consisting of solid lubricants, was observed on the worn surfaces of laser-alloyed layers. It caused an increase in the wear resistance at room temperature. The presence of calcium fluoride and barium fluoride was confirmed in laser-alloyed layers using XRD and X-ray microanalysis by EDS method. Practical implications: Laser surface modification with solid lubricants had the important cognitive significance and gives grounds to the practical employment of this technology for reducing the abrasive wear. Originality/value: The wear mechanism of surface layer with solid lubricants was determined. The produced layer with laser alloying layers of boron and solid lubricant (CaF2 or BaF2) was compared.

The paper presents the data on phase composition and structure forming for the alloys and oxide layers, on distribution of elements among the alloy structural components and oxidation surface through the depth of oxide and sub-oxide layers, on variation of wear resistance, scale resistance, growing stability and mechanical properties of cast iron of Cr-Mn-Ni-Ti-Al-Nb system depending on different aluminium and niobium content and thermal accumulating capacity of a casting mould. Complex carbides (Nb, Ti)C are forming in white cast iron during niobium alloying. Quantitative metallographic analysis of (Nb, Ti)C carbides and (Cr, Fe, Mn)7C3 complex carbides was carried out on the samples with examined composition. The tests for scale resistance were conducted, structure and properties of cast iron were investigated. It was determined that chemical composition and structure of oxide layers depend on distribution of alloying elements among the alloy structural components. It was established that the areas of oxide film surface layer, which were formed on eutectics, contain mainly manganese; its concentration is more than 65 %, while Al is 4 % and Cr is 1 %. Manganese leads to increase of defects amount, such as pores, micro-cracks and vacancies, in oxide film during high-temperature gas oxidation; penetration ability of this film also increases, what has a negative effect on metal resistance to further destruction caused by oxidation. The film becomes porous, its thickness enlarges. Aluminium provides favourable influence on forming of the thin protective spinel-type films (dense substance with good metal adhesion) with minimal amount of defects; diffusion through such oxide film is very difficult. The areas of oxide layer, which were formed on austenite dendrites, contain mainly aluminium; its concentration is more than 24 %, while Mn is 16 % and Cr is 12 %. High aluminium content provides small film thickness. Joint alloying by aluminium and niobium leads to simultaneous increase of heat resistance and wear resistance. Wear resistance increased as a result of enlargement of the part of primary carbides (Nb, Ti)C with high hardness in the structure of cast iron. Composition of oxide films includes aluminium which strengthens their protective properties and rises of the alloy scale resistance. Alloying by niobium leads to secondary hardening during cooling in a casting mould. Dispersion particles of М7С3 carbides are forming in solid state, thereby no structure degradation occurs during testing at increased temperatures, and growing stability rises.

Properties of surface layers produced on the Ti–6Al–3Mo–2Cr titanium alloy under glow discharge conditions

In order to increase hardness and wear resistance, research was conducted on the production of ZrC coatings on medical Ni-Ti alloy by reactive magnetron sputtering. The coatings should exhibit straining capability in a range similar to the magnitude associated with the shape memory effect while maintaining good adhesion to the Ni-Ti alloy.ZrC coatings were deposited by reactive magnetron sputtering in an acetylene atmosphere on Ni-Ti and Si alloy samples. Investigations were carried out in relation to the phase composition (XRD) and the structure (SEM) of the coatings. Hardness, the E-modulus, internal stresses, adhesion (the scratch test, the Rockwell test) and tribological tests (ball-on-disk) of the ZrC coatings deposited at acetylene flow rates in the range 1.5-6.3 sccm were investigated.The XRD investigations confirmed that the coatings contained ZrC phase crystallites. The highest hardness of the ZrC coatings (26.1 GPa) is more than 10 times greater than that of the Ni-Ti alloy (2.3 GPa). The Scratch and Rockwell tests prove good adhesion of the ZrC coatings to Ni-Ti alloy substrates. The dry friction coefficient of ZrC coatings, determined by the ball-on-disk method, is many times lower (0.1-0.3) compared to that of Ni-Ti substrates (0.96). Coatings deposited at acetylene flow rates above 3.5 sccm show an order of magnitude lower wear ratios compared to Ni-Ti substrates.It is planned to carry out additional investigations in relation to the chemical and phase composition using WDX and XPS methods of the ZrC coatings deposited and an EDS analysis from the friction pair surfaces after tribological ball-on-disk tests.The structure and properties of ZrC coatings, deposited using reactive magnetron sputtering, indicate that they can be used to coat, for example, endodontic instruments made of Ni-Ti alloy. Research in this direction is continuing.ZrC coatings significantly increase the hardness and wear resistance of Ni-Ti alloy substrates while maintaining good adhesion. They may be used in various fields of technology and medicine, thus significantly increasing the durability of Ni-Ti alloy components/objects that have so far been in use.

Stellite3-Ti3SiC2-Cu composite coatings on IN718 by laser cladding towards improved wear and oxidation resistance

Recently, silver (Ag) plating for automotive connector has been attracted extensively attention due to the fast progress of HEV/EV system and as a promising candidate material to substitute the costive gold (Au) plating. The Ag plating film possesses the highest conductivity among the metals and excellent corrosion resistance next to Au plating. However, Ag plating suffers a low wear resistance problem because of the soft nature of Ag metal (~80 Hv). Because an oxidation film is difficult to form on silver surface, the corrosion resistance is good. More serious problem of Ag plating is that an adhesion phenomenon often occurs during sliding wear actions as terminal mating materials, because an oxidation film is difficult to form on Ag surface owing to the good corrosion resistance as a noble metal. To solve those problems, many studies focused on fabricate hard Ag plating by adding some alloy elements like Co, Sb, and Se or adding graphite powder into Ag plating films, which improved wear resistance but sacrificed electric conductivity. Here, we propose a new Ag-graphene electro-plating film, with the graphene functioning as solid lubricant and electric component, which may reinforce the wear resistance while without lowering its electric conductivity. The Ag-graphene composite films were fabricated on Cu sheets by a hybrid electrodeposition method, i.e., combining electrodeposition of Ag and electrophoric deposition of graphene nano-flakes, in a non-cyanate plating bath. The graphene nano-flakes were prepared by an electrochemical peeling method from a graphite material. The microstructures, chemical composition, and crystalline structure of the anodized specimens before and after annealed were investigated FE-SEM (EDS), XRD, GD-OES, FT-IR, and Raman spectroscopy. Moreover, the electric resistance meter and wear resistance were also investigated, compared to commercial Ag plating as reference.Figs. 1a and 1b show the surface FE-SEM images of as-electrodeposited pure Ag and Ag-graphene films respectively. It can be seen that, except for the featured Ag nano-particles, some blurry films can be observed on the Ag film in Fig. 1b. The EDS analysis result in Fig.1c demonstrates a strong C peak, indicating the co-deposition of carbon clearly. Moreover, the inclusion of graphene in Ag films were also confirmed by Raman spectra and XRD measurements. The electric resistance of Ag-graphene composite films was equivalent to the commercial Ag films, and the detail results will be reported on the meeting. Figure 1

Use of nanoscaled multilayer and compound films to realize a soft lubrication phase within a hard, wear-resistant matrix

Influence of zirconia and ceria nanoparticles on structure and properties of electrodeposited Ni-W nanocomposites

Improvement in wear resistance of laser-clad Fe–Cr–Mo–B–C-(TiC) amorphous-nanocrystalline coating

Nitriding is as an effective technique applied for many years to improve the surface hardness and wear resistance of low carbon and tool steels [1]. In the case of stainless steels, increase of surface hardness and wear resistance accompany by a drop in corrosion resistance due to the precipitation of CrN. In this respect, many attempts have been made to modify the surfaces of austenitic stainless steels to increase their surface hardness and wear resistance without scarifying the corrosion resistance [2-6]. It is finally concluded that, nitriding at temperatures lower than conventional nitriding process (which is generally about 550°C) has potentiality to produce a nitrogen expanded austenite (also known as S-phase), on the surface without formation of CrN. Due to the superb properties of the S-phase, the low temperature nitrided austenitic stainless steels exhibit very high surface hardness, a good wear resistance, and more importantly, an excellent corrosion resistance. Recently some attempts have been made to apply low temperature nitriding to martensitic stainless steels, which are widely used in the industries of medicine, food, mold and other civil areas [7-9]. In these works, where nitriding has been conducted by plasma processes, superior surface hardness, along with excellent wear and corrosion resistances have been reported for AISI 410 and AISI 420 grade martensitic stainless steels. This work focuses on low temperature gas nitriding of AISI 420 grade martensitic stainless steel in a fluidized bed reactor. In this respect the microstructures, phase compositions, hardness, wear and corrosion behaviours of the original and nitrided martensitic stainless steels have been compared.