Structural transformations in wear resistance of iron- and cobalt-based amorphous alloys during abrasive wear

The wear resistance and structural changes in a number of amorphous alloys based on iron and cobalt and in high-carbon tool steels are studied during wear by a fixed abrasive (crondum, Carborundum) at room temperature and −196°C. The abrasive wear resistance of the amorphous alloys is shown to be 1.6–3.1 lower than that of the high-carbon tool steels having a similar hardness. The relatively low level of the abrasive wear resistance of the amorphous alloys is assumed to be caused by strain softening of their surface during wear. A nanocrystalline structure is found to form in local microvolumes in a thin deformed surface layer of the alloys.     

Wear Resistance of Plasma-Sprayed Coatings in Intensive Abrasive Wear Conditions

The abrasive wear resistance of plasma-sprayed oxide ceramic (Al2O3 and Cr2O3) and clad cermet ((Ti–Cr–C)–30% Ni and (TiC)–30% Ni) coatings was studied. The wear characteristics of the coatings such as wear rates, friction forces, friction coefficients, and wear groove depth determined with two methods were compared. The wear test methods included simulation of the friction process using loose abrasive particles and reciprocal ball-on-disk friction using a diamond indenter. The plasma-sprayed TiC-based coatings showed the lowest wear rate and can be applied to protect equipment parts subjected to intensive abrasive wear. The wear loss of the (Ti–Cr–C)–30% Ni and (TiC)–30% Ni coatings determined by friction against loose abrasive particles was 10–17 μm, while the wear loss of the oxide ceramic coatings was 20–42 μm, being 2–2.5 times higher on average.     

热喷涂Fe基非晶合金涂层的微观结构与摩擦磨损行为

分别采用超音速火焰喷涂工艺和爆炸喷涂工艺,在Q235不锈钢基体上制备Fe基非晶合金涂层,对比研究这2种非晶合金涂层在室温下的干摩擦磨损特性,并探讨摩擦磨损机理.结果表明,与超音速火焰喷涂工艺制备的Fe基非晶合金涂层相比,采用爆炸喷涂工艺制备的涂层更致密,孔隙率为2.1％,显微硬度更高,平均硬度高达1 095.6 HV,且耐磨性更好;并且涂层摩擦因数增至稳定值的时间较短,具有更稳定的摩擦磨损行为.超音速火焰喷涂涂层的磨损形式主要以疲劳磨损为主,而爆炸喷涂涂层的磨损形式为粘着磨损和磨粒磨损的综合作用,并以粘着磨损为主.     

Wear resistance of a plasma-electrospark zirconium diboride-based coating on aluminum alloy D16T

The paper examines the structure, phase composition, and mechanical properties of ZrB₂-based plasma coatings formed on D16T aluminum alloy under different conditions. It is established that coatings with an electrospark sublayer are characterized by stronger adhesion with the substrate as compared with that deposited on the base after conventional sandblasting. The wear resistance of this coating in dry friction is comparable with the monolithic VK15 hard alloy. Laser treatment of the coating in open air decreases the wear by 25% at low sliding rates and simultaneously decreases the hardness by 50%. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 5–6 (455), pp. 53–59, 2007.     

Features of formation and the structure,composition, and properties of electrospark coatings on the ZhS6U nickel alloy with the use of the KhTN-61 SHS-Ts alloy

Features of the mass transfer of a KhTN-61 SHS-Ts electrode material onto a substrate of a ZhS6U nickel alloy with a variation in frequency (1000–1400 Hz) and time (25–70 μs) of pulsed discharges was studied. A complex of studies of the structure, composition, and properties of the formed coatings was carried out. The optimum frequency-energetic mode of the treatment (E = 0.30 J, f = 1000 Hz, and τ = 50 μs), which was characterized by a high rate of coating at a satisfactory degree of the roughness of the surface layer, is found. As a result of electrospark alloying (ESA) at the optimum energetic parameters, 40-μm-thick coatings with a uniformity of 95% and a microhardness of 5.2 GPa form on the surface of the nickel alloy. The ESA treatment of a ZhS6U nickel alloy with the use of KhTN-61 SHS-Ts electrode material allows us to enhance its wear resistance (by more than a factor of 10), hardness (by a factor of 2), and heat resistance, as well as to decrease (by a factor of 5) the friction coefficient.     

Effect of silicon on the wear resistance of high-carbon steels with the structures of isothermal decomposition of austenite during friction and abrasive action

The hardness and wear resistance during sliding and abrasive friction of 80S2 (0.83% C, 1.66% Si) and U8 (0.83% C) steels subjected to the isothermal γ → α decomposition in the temperature range 330–650°C and additional 5-min annealing at 650°C are compared. The optimum decomposition temperature is found to be 550°C. At this temperature, fine lamellar pearlite with the maximum hardness and wear resistance as compared to other pearlitic and bainitic structures forms in the silicon steel. The silicon-alloyed fine lamellar pearlite of 80S2 steel is found to have high hardness and abrasive wear resistance as compared to the similar structure in plain U8 steel; however, this pearlite has no advantages in the wear resistance under conditions of sliding friction on a steel plate. Silicon alloying of the bainitic structures in the eutectoid steel leads to a noticeable decrease in the wear resistance during sliding friction and abrasive action. Friction oxidation is shown to negatively affect the abrasive wear resistance of the silicon steel.     

Changes in Structure and Physicochemical Properties of Spark Coatings Based on TiN and TiB2 after Treatment with Concentrated Solar Radiation

Studies have been made on the structure and properties of spark coatings made of TiN and TiB₂ on steel U8 after treatment with concentrated solar radiation. It is found that the absorption capacity of the steel raised by a factor 2–3. The concentrated radiation reduces the coefficient of friction of the spark coatings made of TiN and TiB₂ by a factor 1.4, while the wear rate is reduced by a factor 1.6–2 by comparison with the untreated material. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 64–69, July–August, 2005.     

Ni-Ni3B composite coating

The paper compares the microstructure and tribotechnical characteristics of composite coatings of 70 wt.% Ni-20 wt.% Cr-5 wt.% Si-5 wt.% B. These coatings are produced by slip casting and unidirectional solidification. The coating composition is substantiated and coating restructuring mechanisms in the forming process are discussed. Natural composite Ni-Ni₃B forms the basis of the coating. The fine lamellar eutectic, which occupies ∼50.5% of the coating, consists of Ni₃B, a nickel solid solution doped with chrome and silicon, and CrB crystals. The microhardness of the coating and phase constituents are determined. The method of contact eutectic vacuum melting with controlled cooling permits obtaining the nonporous coating without slag inclusions and with homogeneous oriented structure. The mechanism of 3 to 5 times increase in the wear resistance of homogeneous nonporous coatings and their potential application in friction units of machinery are discussed. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 40–47, 2007.     

Coatings Deposited by the High-Velocity Flame Spraying Method

The properties (porosity, hardness, wear resistance) of coatings obtained by high-velocity flame spraying were studied. It was shown that high-velocity spraying produces highly dense coatings (porosity below 3%) which have good abrasion resistance under extreme conditions: resistance to abrasive-erosion was 10-12 times better than that of uncoated steel. Abrasive wear resistance at low attack angles was obtained in coatings of maximum hardness, i.e., hardness above that of the abrasive. At high attack angles an optimum ratio of hardness to ductility is desired. The optimal structure for WC Co coatings is the so-called twice cemented hard alloy structure, in which granules or particles of WC Co are included within the cobalt binder. At large attack angles the concentration of carbide phase should exceed 50%, and at normal angles is optimally 20-30%.     

Structure and properties of nickel-chrome diboride composite electrolytic coatings

Conclusions The addition, to the CEC based on nickel, of up to 6% fine-dispersion powders of chrome diboride (in their position in the vertical cathode) and of more than 16.4% micropowders (on the horizontal cathode) with subsequent vacuum annealing at temperatures ranging from 400 to 1100°C makes it possible to produce wear and corrosion-resisting coatings of three types: the coatings consisting of a nickel matrix alloyed with chrome, with uniformly distributed inclusions of Ni₃B, coatings consisting of an eutectic boride frame filled with a solid solution of chrome in nickel, and coatings consisting of an eutectic boride matrix which contain specially oriented columnar crystals of the boride of complicated composition (Ni₂CrB₂).Isothermal annealing of the nickel-chrome boride CECs results in high adhesion to the steel substrate and gas-abrasive resistance and increases by an order of magnitude the wear resistance in sliding friction in the corrosion-active acid medium. This is explained by the formation, in the coating, of eutectic structures with spatially oriented crystals of the boride which contains nickel and chrome.Translated from Poroshkovaya Metallurgiya, No. 3(315), pp. 54–59, March, 1989.     

Plasma coatings of (TiCrC)-(FeCr) composite powder alloys: Structure and properties

The coatings of the (TiCrC)-(FeCr) composite are deposited on steel and titanium alloy by plasma method. The composition, structure, and tribotechnical properties of these coatings are studied in comparison with traditional materials based on the Ni-Cr alloy. The effect of preliminary surface treatment methods, i.e., sandblasting treatment and electrospark alloying, on coating properties is examined. The fretting corrosion of coatings is investigated. It is established that coatings based on double titanium-chromium carbide have considerably greater wear resistance than that of Ni-Cr alloys at almost equal friction coefficients. It is established that electrospark alloying is competitive with traditional sandblasting treatment in environmental effect and coating-to-based adhesion. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 37–45, 2007.     

Effect of combination of gas phase deposition and electric-spark alloying on wear resistance of VK8 (WC-8% Co) hard alloy

The composition and structure of heterophase coatings on VK8 (WC-8% Co) hard alloy cutting blades (inserts) were studied. The coatings were obtained by the methods of CVD of TiC with double magnetic-abrasive treatment and electric-spark alloying (ESA) with a TiCN-AlN-based composite as well as by combining these two methods. The wear resistance of WC-Co cutting blades with combination coatings was the best in tests on cutting the materials from SCh20 cast iron. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(450), pp. 49–55, July–August 2006.     

Tribological properties of detonation coatings based on titanium aluminides and aluminum titanate

Operation of coatings based on tialite, γ-TiAl, titanium aluminides with discrete inclusions of TiN and also alloys based on cobalt, nickel, and titanium in friction pairs with polyethylene grade “Chirulen” and stainless steel 12Kh18N10T is studied. It is established that tialite coatings formed from nanostructure powders of Ti-Al by detonation deposition are the best for operation under dry friction conditions in a pair with stainless steel 12Kh18N10T (minimum friction coefficient and minimum wear of the contact surfaces). It is shown that in the sliding rate range selected effective operation of material in friction pairs with polymer is provided due to transfer it to the contact surface and formation between rubbing surfaces of a thin film fulfilling the function of a solid lubricant. It is established that stable operation with the minimum wear in a friction pair with polyethylene grade “ Chirulen” is provided by a coating of γ-TiAl and Al₂TiO₅, and also coatings based on titanium aluminide with fine TiN inclusions.     

Mechanical and tribological properties of TiN and SiCN nanocomposite coatings deposited using methyltrichlorosilane

The paper examines nanocomposite coatings based on TiN and SiCN obtained by plasma-enhanced chemical vapor deposition (PECVD) using methyltrichlorosilane (MTCS) as one of the precursors. The nanocomposite coatings demonstrate four types of structures depending on deposition modes: nc-TiN, nc-TiN/a-SiCN, nc-TiNC/nc-TiSi₂/a-SiCN, and nc-TiNC/nc-TiCl₂/a-SiCN. The nanohardness and elastic modulus of the coatings reach 31 and 350 GPa, respectively. The coatings on substrates of hard alloys, high-speed steel, and silicon increase the nanohardness of the base from 10 to 100%. The correlation between the H/E ratio and wear resistance is not observed. The coatings deposited at low radiofrequency powers demonstrate good adhesion to silicon substrates. It is shown that the use of MTCS as the main precursor allows one to obtain hard and wear-resistant nanocomposite coatings. __________ Translated from Poroshkovaya Metallurgiya, Vol. 47, No. 1–2 (459), pp. 125–133, 2008.     

Erosion-resistant coatings for gas turbine compressor blades

The effect of ion-plasma coatings made from high-hardness metal compounds on the erosion and corrosion resistance and the mechanical properties of alloy (substrate) + coating compositions is comprehensively studied. The effects of the thickness, composition, deposition conditions, and design of coatings based on metal nitrides and carbides on the relative gas-abrasive wear of alloy + coating compositions in a gas-abrasive flux are analyzed. The flux contains quartz sand with an average fraction of 300–350 μm; the abrasive feed rate is 200 g/min; and the angles of flux incidence are 20° (tangential flow) and 70° (near-head-on attack flow). Alloy + coating compositions based on VN, VC, Cr₃C₂, ZrN, and TiN coatings 15–30 μ m thick or more are shown to have high erosion resistance. A detailed examination of the coatings with high erosion resistance demonstrates that a zirconium nitride coating is most appropriate for protecting gas turbine compressor blades made of titanium alloys; this coating does not decrease the fatigue strength of these alloys. A chromium carbide coating is the best coating for protecting compressor steel blades.     

Protective properties of detonation-deposited coatings from powders alloyed with aluminum and boron

Conclusions The corrosion resistance of detonation-deposited coatings from aluminum- and boron-containing PKh20N80 alloy, nickel, and stainless steel powders markedly surpasses that of constructional steel. The electrochemical properties of such detonation-deposited coatings are determined by their composition and thickness. The basis material is effectively protected against corrosion by 600-Mm-thick coatings. Under conditions of corrosive and mechanical wear detonation-deposited coatings from aluminum- and boron-containing 20% Cr-80% Ni alloy, nickel, and stainless steel powders operate satisfactorily under loads of not more than 5 MPa. The results of service tests have demonstrated the usefulness of detonation-deposited coatings from alloyed powders. Coating with powder of composition III was found to increase the useful life of certain parts of spraying equipment two to two and a half times.Translated from Poroshkovaya Metallurgiya, No. 8 (272), pp. 52–55, August, 1985.     

热处理对Fe基非晶合金涂层的相组成及摩擦磨损行为的影响

采用爆炸喷涂技术在Q235不锈钢基体上制备Fe基非晶合金涂层,在500~700℃下对涂层进行热处理,研究热处理温度对涂层的相组成和摩擦磨损性能的影响。结果表明:随热处理温度升高,涂层中非晶相含量明显减少,700℃热处理后,非晶相含量(体积分数)由热处理前的85.54%降至38.94%;热处理后涂层结构变得更致密;喷涂态涂层的平均显微硬度为1 095.6 HV0.05,500℃热处理后硬度变化不大,随热处理温度升高呈缓慢上升的趋势;与喷涂态涂层相比,500和600℃热处理后涂层的平均摩擦因数稍有增加,而700℃热处理后平均摩擦因数减小15%;热处理温度为600℃时涂层的磨损量较热处理前降低20%,耐磨性能最好,而热处理温度为700℃时涂层的质量磨损增大到热处理前的3倍以上,主要是涂层晶化相明显增加,氧化物含量增多,涂层变脆所致;磨损机制为则由喷漆态的粘着磨损向磨粒磨损,再到二者混合机制磨损转变。     

Properties of nanolayer erosion-resistant coatings based on metal carbides and nitrides

Vacuum-arc ion-assisted deposition is used to form nanolayer protective 2D coatings based on the nitrides or carbides of titanium and chromium, vanadium carbide, and aluminum nitride with a layer thickness of 5–80 nm and a total thickness up to 25 μm. The phase composition of the coatings is studied after deposition and tests. Titanium alloy VT1-0 (EP866 steel)-nanolayer coating compositions are subjected to hot-strength and rapid cyclic corrosion tests, and the erosion resistance of the 2D nanolayer coatings in a dust-air flux (the average fraction of quartz sand is 300–350 μm) is studied. Among the 2D nanolayer coatings on titanium and steel substrates, a composition of VT1-0 alloy with a TiN/CrN coating at a nanolayer thickness of 60–70 nm and a total thickness of 19 μm has the maximum erosion resistance. The erosion resistance of the TiN/CrN coating is shown to decrease with decreasing nanolayer thickness, and it has a high thermal stability after holding at 700°C for 100 h.     

激光熔敷Ni60／WC合金层的腐蚀磨损特性

研究了４５钢表面激光熔敷镍基ＷＣ合金层的耐蚀性及在不同冲击速度和不同浓度酸性介质下的腐蚀磨损特性。结果表明，激光熔敷Ｎｉ６０／ＷＣ合金层不论耐蚀性还是抗腐蚀磨损性能同于２Ｃｒ１３不锈钢。应用微机对试验结果进行逐步回归分析，得出了影响因素与腐蚀磨损速度的害量关系，并探讨了熔敷层的腐蚀磨损过程。     

工艺参数对超音速火焰喷涂Fe基非晶涂层性能的影响

Fe基非晶涂层具有优异的耐磨、耐蚀性能,以及较高的性价比,适合在表面防护涂层领域广泛应用。本文通过正交试验研究了煤油流量、氧气流量、送粉速率、喷涂距离对超音速火焰喷涂制备的Fe基非晶涂层的孔隙率、硬度、耐磨性能的影响。采用图像法、显微硬度计和摩擦磨损试验机分别对Fe基非晶涂层的孔隙率、硬度、耐磨性能进行了表征。采用X射线衍射仪和扫描电镜分别对涂层的相组成和显微结构进行了表征。通过极差分析法分析得出以涂层孔隙率最低为目标的优化制备工艺,最佳喷涂工艺参数为:煤油流量0.41 L/min,氧气流量830 L/min,喷涂距离430 mm,送粉速率40 g/min。结果表明:送粉速率和氧气流量对涂层孔隙率影响较大,进而影响涂层的硬度及耐磨性能。孔隙率随着氧气流量和送粉速率的增加而增加,随着煤油流量和喷涂距离的增加而降低。制备的Fe基非晶涂层硬度达到1158.9HV0.2,孔隙率为1.22%,磨损实验的质量损失量只有316L不锈钢的一半。