The influence of carbonitriding conditions on microstructure and mechanical properties of 25CrMo4 low-alloy steel

Abstract

Carbonitriding is an important industrial process applied for the improvement of the mechanical characteristics of the component of many steels employed in several machines parts like cam shafts, crank shafts and gears to enhance fatigue strength and wear resistance. In this study, the influence of the gaseous carbonitriding on the enhancement of surface characteristics and mechanical properties was investigated using different parameters for low alloy steel. The analysis and characterization of the treated material were carried out employing optical microscopy (OM) and scanning electron microscopy (SEM) and X-ray diffraction methods (retained austenite and residual stresses). Microhardness and tensile tests were performed and the fracture mechanisms of the various materials were ultimately examined and discussed. The main contribution of this research work is to show and optimize the selection of the appropriate parameters for this kind of steel in industrial field. Diffusion mechanism and microstructure proved that the process of high temperature gas carbonitriding allowed enhancing the mechanical properties of material. This process resulted in a rise of the yield strengths and a loss in a pronounced ductility associated with the brittle intergranular fracture surface caused by the nitride precipitation in the grain boundaries.

Investigation of friction and wear resistance of carbonitrided AISI 4130 steels using single and multi-pass scratch technique

“…This layer is composed of martensitic needles comprising Fe3C carbides and retained austenite. 8 The XRD graph of carbonitrided AISI 4130 low alloy steel at different carbon concentrations are shown in Figure 4. Although the structure consisted of austenite phase, ε(Fe2−3CN), γ′(Fe4N), and chromium nitride precipitates were observed in the carbonitrided samples depending on carbonitriding parameters.…”

“…11 In this regard, several studies have been conducted on the microstructural and mechanical properties of carbonitriding treatment, using plasma 12 and gas carbonitriding. 8 Thi Chieu et al 13 found that the microhardness of carbonitriding SCM420 was enhanced from 40 HRC for the untreated material to 65 HRC. In addition, Hoja et 14 found that the carbonitriding treatment improved the wear resistance of forging dies.…”

“…Similarly, carbonitriding is becoming the focus of attention for researchers, 7 it becomes widely used for surface engineering due to its short production cycle, low cost, and strong size adaptability in carbonitrided specimen. 8 This treatment consists in enriching the surface in carbon and nitrogen by diffusion in the austenitic domain (825 to 900°C) followed by a quenching. 9 The carbonitriding exhibit a higher hardness and wear properties than the carburizing treatment.…”

The Influence Mechanism of HSLA Weld Metal with Different Composition on High‐Temperature Strength

“…The heat treatment of experimental cast steel adopts a simple process of normalizing + high‐temperature tempering. [ 17 ] The sample is put into a box‐type resistance furnace filled with nitrogen, heated to 880 °C for 1 h, cooled in air to room temperature, then tempered within 520–650 °C, kept for 1.5 h, and air‐cooled to room temperature.…”