Orthogonal cut of SPS-sintered composites with ferrous matrix and Fe Mo S particles: Numerical and experimental analysis

Abstract

Metal-matrix composites with solid lubricant reinforcements may present a suitable alternative to improve the tribological behavior of sintered components. Besides the performance during the application, the presence of solid lubricants may also modify component manufacture, for example, during machining operations to achieve complex shapes not directly obtained from the sintering process. This work describes a numerical and experimental analysis on the orthogonal cut of metal-matrix composites composed of FeMoS particles embedded in an Astaloy 85 Mo (Höganäes AB) matrix. Specimens were prepared using the Spark-Plasma Sintering (SPS) technique, from mixtures containing powders of Astaloy 85 Mo steel and 2 wt% or 4 wt% of molybdenum disulfide (MoS2). An unreinforced Astaloy 85 Mo specimen (without MoS2) was also included in the analysis. Different microstructures were observed after SPS. The unreinforced specimen presented a ferrite-pearlite structure with a porosity level below 2% and the specimen sintered with 2 wt% of MoS2 presented iron sulfide particles dispersed in the steel matrix. The structure of the specimen sintered with 4 wt % was more complex, with two distinct phases dispersed in the Astaloy 85 Mo matrix. Experimental orthogonal cuts were conducted on the three specimens using a shaper machine tool equipped with a tungsten carbide (WCCo) cutting insert. Tests were recorded using a high-speed camera. The machined surfaces were later analyzed with an optical profilometer and in a scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS). The chips were also characterized. The cutting operation was simulated by two-dimensional (2D) finite-element analysis. The meshes were prepared based on the specimen microstructures and considering the properties of the individual phases. Results have indicated significant differences in the cutting process. Observation of the chip surfaces indicates plastic deformation on the unreinforced specimen, in opposition to more uniform scratches on the composite surfaces, especially that of the specimen sintered with 4 wt % of MoS2.