Cu-Based MoS₂-Dispersed Composite Material Formed by the Compression Shearing Method at Room Temperature

Abstract

Cu/MoS 2 composite material was formed by a novel powder-molding technique, which is termed the compression shearing method at room temperature (COSME-RT). Cu/MoS 2 sample mechanical and tribological properties and microstructures were investigated. Samples were prepared using five different MoS 2 concentrations between 0 to 20 vol.%. No unwanted compounds were generated by the Cu and MoS 2 because a high temperature is unnecessary in COSME-RT. Scanning electron microscopy observations confirmed that the MoS 2 particles were dispersed homogeneously in the Cu host matrix. The indentation hardness of Cu/MoS 2 with 0, 1.0 and 5.0 vol.% MoS 2 was higher than 1.6 GPa, and is higher than that formed by conventional powder metallurgy methods and a pure Cu plate. The indentation hardness of the Cu/MoS 2 decreased with increasing MoS 2 concentration. In contrast, the lubricating performance of MoS 2 became more pronounced at 5.0 vol.% or above. The coefficient of friction of Cu/MoS 2 with 5.0, 10 and 20 vol.% MoS 2 was ~0.20, and is the same as for MoS 2 in air. The sample coefficient of friction was maintained because of lubrication by forming a transferred film of wear debris that contained MoS 2 . Cu/MoS 2 had a low coefficient of friction, but maintained its material strength at 5.0 vol.% MoS 2 .

Role of MoS₂ Addition in the Consolidation of Metal from Powder to Plate by the Compression Shearing Method at Room Temperature

“…A mixed powder with a MoS 2 concentration r = 5.0 vol.% was prepared. The r = 5.0 vol.% sample showed the lowest coefficient of friction and a high mechanical strength, according to our previous study [19].…”

“…These powders were the same as those used in a previous study, and the average particle sizes for the Cu and MoS 2 were 38 and 6.0 μm, respectively [19]. A mixed powder with a MoS 2 concentration r = 5.0 vol.% was prepared.…”

“…Unlike the abovementioned conventional methods, elevated temperatures are not required in the COSME-RT process, because powder particles are bonded by a friction process that results from the two applied forces. Therefore, materials can be formed without a coarsening of their crystal grains or compound generation [19]. The material that is formed by COSME-RT exhibits a high material strength from the Hall-Petch effect [20,21], because a fine crystalline feedstock powder structure is maintained during the forming process.…”

“…In a previous study, the development of a Cu-based MoS 2 -dispersed composite was attempted and the composite exhibited a low friction coefficient and a high material strength [19]. Microstructural studies of the Cu/MoS 2 sample indicated that the bonding and crystalline grain refinement of Cu powder particles of Cu/MoS 2 were incomplete compared with the pure Cu sample.…”

“…Several methods to form composites, such as powder metallurgy and casting-based methods have been attempted to achieve such requirements [1][2][3][4][5][6][7]. In recent years, our research group has focused on a novel powder-molding method, the compression shearing method at room temperature (COSME-RT) [8][9][10][11][12][13][14][15][16][17][18][19], to meet the material requirements. COSME-RT is used to form a thin plate by applying a simultaneous compressive stress and shearing strain to a powder material at room temperature and in an ambient atmosphere.…”