Scouring erosion resistance of metallic materials with composite microstructures

Effects of tungsten on erosion–corrosion behavior of high chromium white cast iron

In this present study, wear behaviours of high chromium white iron valve seat inserts and tappets used in the automotive sector were investigated. Wear behaviours of three different rates of high chromium white cast irons (containing 10, 12 and 14% chromium) were examined under heavy service conditions. For that purpose, the produced valve seat inserts were characterized through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD) and hardness measurements. They were tested at a sliding speed of 1 ms−1, under 120 N load and for six different sliding distances (500, 1000, 1500, 2000, 2500, 3000 m) by using a standard wear apparatus (pin-on-disk type). The result showed that as the amount of Cr increased in the alloys, their hardness decreased. The decrease in the hardness were considered to be as the result of transformation of M7C3 carbides into M23C6 carbides in the structure. This decrease in hardness with increasing chromium content also increased the weight loss. Thus, it was determined that the white iron with 14% Cr (which had a greater amount of M23C6 carbides) was subjected to the highest wear.

Effect of titanium on the morphology of primary M 7C 3 carbides in hypereutectic high chromium white iron

High-alloyed white cast irons are an important group of materials whose production must be considered separately from that of ordinary types of cast irons. The metallic matrix supporting the carbide phase in the high-alloy white cast irons can be adjusted by alloy content and heat treatment to develop proper balance between resistance to abrasion and toughness needed to withstand repeated impact. This article provides a brief discussion on the heat treatment, mechanical properties, and chemical compositions of high-alloy white cast irons such as nickel-chromium white irons and high-chromium white irons.

The relationship between Cr/C and properties of Fe‐C‐Cr high chromium white irons was studied by calculating the valence electron structure of austenite of Fe‐C‐Cr high chromium white irons with the empirical electron theory of solids and molecules (EET) and the equilibrium phase diagram of Fe‐C‐Cr system. Results show that the C‐Cr bond is the strongest bond of all bonds in alloying austenite in Fe‐C‐Cr high chromium white irons of industrial application and, thereby, causes partial aggregation of C‐Cr atomic groups. The weight of partial aggregation of C‐Cr atomic groups would be increased greatly and more austenite would be reserved to room temperature when Cr/>6. The Fe‐CCr high chromium white irons achieve best mechanical property when Cr/C=5.5‐6.5.

Microstructural effect and wear performance of high chromium white cast iron modified with high boron contents

The study aimed to investigate the effects of wear parameters including impact energy, impact frequency, test time, and their interactions on the impact wear characteristics of high chromium white iron (HCWI) and zirconia toughened alumina (ZTA) reinforced HCWI composites fabricated by squeeze casting method using response surface methodology (RSM). The Box-Behnken Design (BBD) method was employed, and a linear model was developed to describe the relationship between wear loss and wear parameters, and to predict the wear behavior of the tested materials. The parameters of energy, frequency, and test time were found to be statistically significant, and positively influencing the wear behavior. Specifically, test time emerged as the most influential factor, followed by energy and frequency. The wear characteristics of HCWI are primarily characterized by shallower plowing and furrows, partial plastic deformation, surface spalling, and inserted abrasives. In contrast, the predominant wear mechanisms for ZTA/HCWI composites include slight breaking of ZTA particles, plowing, and cutting of the metal matrix; breaking and falling of ZTA particles; broken abrasive particles encrusted into the matrix; and the formation of spalling pits.

Barite sulfate (BaSO4) is considered a very important mineral material employed as a weighting agent for all types of drilling fluids. Meanwhile, crushers used for the grinding step during barite crushing are affected by catastrophic wear damage located in the hammer parts made from high chromium white cast iron (HCWCI). In the present study, a comparison of the tribological performance between HCWCI and heat-treated steel AISI P20 was conducted to investigate the possible substitution of HCWCI. The tribological test was performed under normal loads between 5 and 10 N for different durations (60, 120, 180, and 240 min). The wear response analysis for both materials showed that the friction coefficient increases as the applied load increases. Moreover, AISI P20 presented the lowest value compared to that attributed to HCWCI in all conditions. Furthermore, the analysis of the wear track obtained by means of scanning electron microscopy (SEM) revealed that the damage was an abrasive wear phenomenon for HCWCI with detection of a crack network throughout the carbide phase, which was more pronounced under the highest load. Regarding AISI P20, an abrasive wear mechanism was detected, characterized by several grooves and ploughing phenomena. Further, the analysis of the wear track using 2D profilometry revealed that for both loads, the maximum wear depth of the HCWCI wear track was significantly greater than that of AISI P20. As a result, when compared to HCWCI, AISI P20 exhibits the best wear resistance. Furthermore, as the load increases, the wear depth and the worn area increase as well. Also, the wear rate analysis supports the previous findings, which showed that under both loads, AISI P20 was more robust than HCWCI.

Erosive wear and impact damage of high-chromium white cast irons

In this investigation, the microstructure changes of 0.25% low carbon steel, which is hardfaced with high chromium white iron by a semiautomatic welding process was studied using OM, SEM and EDX analysis. Mechanical properties, such as hardness and wear rates, were also investigated. Four groups of samples were used in the study. The first group of samples was low carbon steel without any surface treatment. The second, third, and fourth groups of samples were selected from several hard-faced low carbon steel pieces with 3.0, 3.4 and 3.8 % of chromium contents in their hard-faced surface respectively. SEM analysis results show that the microstructure of the surface treated samples consist of a small amount of ferrite and a large amount of pearlite. EDS test shows that the chromium contents of both ferrite and pearlite have increased significantly. Increasing pearlite amounts and increasing chromium concentrations in every phase seem to increase the hardness from 280 to 495 HV30. Chromium content was increased in both pearlite and ferrite. This increase causes the phase’s hardness to be increased. Also, there is a trace of М7С type carbides that appeared in hardfaced surface with higher chromium content.

Effect of MXene Ti3C2Tx in situ formed TiCx on oxidation behavior of high chromium white iron

The aim of this study is to evaluate the effect of electromechanical treatment on the structure and wear behavior of plasma-sprayed nickel coatings. The coatings were air plasma sprayed on low carbon steel substrates, then electromechanically treated using different values of current density. Erosion resistance was assessed based on volume loss and coating microstructure and phase composition were evaluated via SEM and XRD. Erosion mechanisms were compared by analyzing coating cross-section and surface microstructures and wear resistance was associated with features such as defects, porosity, and cracks.

Damage by indentation and single impact of hard particles on a high chromium white cast iron

Pure alumina coatings deposited on metallic substrates by plasma spraying in air (APS) and in low vacuum (VPS) were subjected to erosive wear by silica sand particles at 50 m s−1. The AP S coatings were porous and exhibited poor resistance to erosion. The VP S coatings produced at high substrate temperatures and lower chamber pressures exhibited low porosity and good erosion resistance, while those deposited at lower substrate temperatures and higher chamber pressures were more porous and eroded more rapidly, in some cases with erosion rates higher than those of the AP S coatings. A pronounced lamellar structure was found to be the most important factor in reducing the erosion resistance. The extent of the lamellar structure and the coating porosity depended on the spraying conditions. For VPS coatings the effects of residual stresses arising from differential thermal contraction were studied by using substrates with different thermal expansion coefficients and by controlling the substrate temperature during spraying. Microstructural effects in these experiments obscured any clear influence of residual stress on erosion behaviour, although there were indications that high residual stresses may lead to microcracking which in turn may promote more rapid erosion.

The microstructure and microhardness of eleven volumetric cermets based on TiC carbide with nickel and cobalt based matrices after liquid-phase sintering at a temperature of 1400 °C were studied. It is supposed to use the research results for the subsequent formation of a powder for plasma spraying of coatings. The compositions of the matrix, additional hardening phases, and carbon were selected taking into account the specific features of the formation of plasma coatings: a decrease in the carbon content and high solidification rates of the sprayed particles with the formation of additional nanosized carbides and an increase in the volume fraction of carbides from 70 % to 88 %. As the matrix, we used the traditional composition for cermets with TiC carbide, NiCr – Mo, and industrial powders, PGSR brands, Ni – 13.5 Cr – 2.7 Si – 4.5 Fe – 0.37 C – 1.65 B, and TAFA 1241F Co – 32 Ni – 21 Cr – 8 Al – 0.5 Y. The ring zone on TiC carbide is formed with the participation of WC, Cr3C2, TiN, matrix phases and additional carbon in the composition of cermets, 1 – 2.8 %, as a result, the initial volume fraction of TiC carbide increases 70 to 88 %. Additional carbon is consumed to reduce oxygen content at the stage of sintering (reduction of oxides). After sintering, cermets have high microhardness values at a load on an indenter of 20 G, 1940 – 3210 kgf/mm2, and lower values at a load on an indenter of 200 G, which was explained by a scale factor. The maximum calculated contribution of the hardness of the hardening phases to the hardness of the cermet was established for cermets with a Co matrix of 3681 kgf/mm2.