The Influence of the Matrix Microstructure on Abrasive Wear Resistance of Heat-Treated Fe–32Cr–4.5C wt% Hardfacing Alloy

The abrasion wear resistance of Fe–32Cr–4.5C wt% hardfacing alloy was investigated as a function of matrix microstructure. In this study, the alloy was deposited on ASTM A36 carbon steel plates by the shielded metal arc welding (SMAW) process and the as-welded matrix microstructure was changed into ferrite, martensite, and tempered martensite by heat treatment processes. The Pin-on-disk test results show that under low (5 N) and high (20 N) load conditions, the wear resistance behavior of the as-welded matrix sample is 20 and 15% higher, respectively, than the martensitic matrix sample, although the bulk hardness of the as-welded matrix is 5% lower. The ferritic matrix sample has the poorest wear resistance behavior which is less than half of that of the as-welded matrix one. Micro-ploughing, micro-cutting, and micro-cracking are recognized as the micro-mechanisms in the material removal in which the proportion of micro-ploughing mechanism increased by increasing matrix toughness.     

Effect of Titanium and Nitrogen Additions on the Microstructures and Three-Body Abrasive Wear Behaviors of Fe–B Cast Alloys

This study investigates the effect of titanium and nitrogen elements on the microstructures and wear behaviors of medium carbon Fe–B cast alloy. The as-cast microstructures of Fe–B cast alloy consist of the eutectic boride, pearlite, and ferrite. Moreover, the as-cast eutectic boride structures are greatly refined when titanium and nitrogen are added. The boride area fraction, average boride area, Rockwell hardness, etc., are also investigated systemically. The wear behaviors of medium carbon Fe–B cast alloy are studied by a three-body abrasive wear tester. The results show that the wear weight loss of Fe–B cast alloy with titanium and nitrogen elements is lower than that of the ordinary Fe–B cast alloy. Meanwhile, the wear mechanism of Fe–B cast alloy with different titanium and nitrogen concentrations is described and analyzed.     

Effects of Ni and Mn on the Cavitation Erosion Resistance of Fe–Cr–C–Ni/Mn Austenitic Alloys

The effects of Ni and Mn concentrations on the cavitation erosion behavior of Fe–12Cr–0.4C–xNi/Mn (x = 5, 7, and 10) alloys were investigated with respect to strain-induced γ → α′ and γ → ε phase transformation. The cavitation erosion resistance of the Ni-added alloys decreased with increasing Ni concentration, whereas that of the Mn-added alloys improved with increasing Mn concentration. Also, the 7Mn-added alloy and 10Mn-added alloy, which additionally underwent the γ → ε phase transformation, had better resistance to cavitation erosion than the 5Mn-added alloy in which the γ → α′ phase transformation occurs most actively. These behaviors were considered to be due to the fact that the strain-induced ε martensite absorbs the cavity collapse energy and prevents the damage by cavitation erosion more effectively than the strain-induced α′ martensite.     

The Microstructure and Wear Characteristics of Cu–Fe Matrix Friction Material with Addition of SiC

The Cu–Fe matrix continuous braking friction materials using SiC as abrasive were fabricated by powder metallurgy technique, and the effect of content and size of SiC were investigated. The tribological properties of friction materials sliding against AISI 1045 steel ring were carried out on a block-on-ring tester at different loads and sliding speeds. The strengthening effect of nano-SiC (55 nm) was superior to that of micro-SiC (70 μm) of the tribological properties for friction materials. The friction coefficients of friction materials increased with increasing nano-SiC content. However, the wear rates decreased with increasing nano-SiC content and then increased when the content of nano-SiC particle exceeded 10 wt%. The specimen contained 10% nano-SiC had the best tribological properties at different testing conditions.     

Wear resistance of cast Fe–Cr–C steels with various combinations of structural constituents at high velocities of sliding

The positive effect of the additional alloying of cast Fe–Cr–C steels on the formation of a secondary structure in the steels and their tribological characteristics under boundary friction has been shown. This effect leads to a decrease in the wear rate of the cast steel 1.2–5.2 times compared to that of the commercial 95Kh18 steel depending on the alloying system of the steels.     

Strain-Induced ε/α′ Martensitic Transformation Behavior and Solid Particle Erosion Resistance of Austenitic Fe–Cr–C–Mn/Ni Alloys

The strain-induced ε/α′ martensitic transformation behavior and resistance to solid particle erosion was investigated for austenitic Fe-12Cr-0.4C-xMn/Ni (x = 5, 7, and 10 wt%) alloys. The γ → α′ chemical driving force decreased with increasing Mn and Ni. The SFE values of 5Ni, 7Ni, and 10Ni alloys were 31.2, 41.5, and 45.8 mJ/m², respectively. Because Ni increased the SFE, γ → α′ phase transformation was suppressed in Fe-12Cr-0.4C-Ni alloys. The SFE values for 5Mn, 7Mn, and 10Mn alloys were 19.4, 16.6, and 10.5 mJ/m², respectively. Although Mn decreased the SFE, the fraction of transformed α′ decreased with increasing Mn concentrations due to γ → ε phase transformation and decreasing γ → α′ chemical driving force of higher Mn alloys. The solid particle erosion resistance was better in the phase transformable alloys than the non-phase transformed alloys. In particular, γ → α′ phase transformable alloys had better resistance to solid particle erosion than γ → ε phase transformable alloys.     

The Study of Arc Rate,Friction, and Wear Performance of C/C Composites in Pantograph–Catenary System

A series of tests on arc rate, friction coefficient, and wear rate of electrical current collectors sliding against overhead contact wires under different conditions was carried out on a high-speed friction and wear testing machine with a pin-on-disc configuration. The worn surface morphology and composition were examined using a scanning electron microscope and energy dispersion spectrum analyzer, respectively. The effects of current, velocity, and load on the arc rate, friction coefficient, and wear rate of C/C composites/QCr0.5 couples were investigated, and the influence mechanism of test parameters on C/C composites was explained. It is concluded that the wear rate increases with an increase in current and velocity and has a decreasing trend with the increase in load. The friction coefficient increases with an increase in velocity and load. The arc rate of C/C composites/QCr0.5 couples increases with an increase in current and velocity. Under the condition of the same current and velocity, when the load is 70 N, the arc rate is the lowest.     

Erosion-oxidation of uncoated,aluminized and chromized-aluminized 9Cr–1Mo steels under fluidized-bed conditions at 550–700 °C

Protective coatings, deposited mainly by thermal spraying and diffusion techniques, are considered a solution to extend the lifetime of many components in the energy production sector, such as heat exchangers. In this paper, some results are presented for uncoated, aluminized and chromized-aluminized 9Cr–1Mo steel, subjected to air and to impacts by 200 μm silica particles at angles of 30° and 90° and speeds of 7.0–9.2 m s^?1 at 550 –700 °C, in a laboratory fluidized-bed rig, to determine whether or not aluminized and chromized-aluminized diffusion coatings could protect the steel under such conditions. Erosion-oxidation damage was characterized by measurement of the mean thickness changes using a micrometer and examination of worn surfaces by scanning electron microscopy.Under most conditions, the coatings provided some protection to the substrate: under 30° impacts, up to 650 °C, and under 90° impacts, at 700 °C, both coatings were effective, whereas under 90° impacts, up to 650 °C, only the chromized-aluminized coating gave significant protection. However, for 30° at 700 °C, the oxide scale on the substrate was protective and the coatings were not needed. Explanations for these observations are presented in this paper, in terms of interactions between the erosion and oxidation processes for the materials.