Tribological properties of copper molybdate powder solid lubricants under high temperature conditions

Abstract

In our previous research, it was suggested that a sort of copper molybdate Cu 3 Mo 2 O 9 generated on the friction track of aluminum bronze coated with MoO 3 powder reduced friction under high temperature conditions. In order to study the lubricity of copper molybdate as high temperature lubricant, the lubrication properties of two kinds of copper molybdate powders, CuMoO 4 and Cu 3 Mo 2 O 9, were studied by comparing with the lubricity of CuO and MoO 3 powders. These powders were supplied to the sliding surface of the stainless steel specimens as solid lubricant and the friction test was conducted at various ambient temperatures ranging from room temperature to 700°C. Cu 3 Mo 2 O 9 and CuMoO 4 powders were synthesized by heating the mixture of CuO and MoO 3 powders in their own specific heating conditions and identified by XRD. Both of Cu 3 Mo 2 O 9 and CuMoO 4 powders showed lower friction coefficient and smaller wear amount of specimen with increasing ambient temperature. On the other hand, CuO and MoO 3 powders showed poor lubricating ability and high wear amount of specimens comparing with two kinds of copper molybdate powders. It was suggested that the enhanced maintaining abilities of copper molybdate on the stainless steel substrate at high temperature and generation of unoxidized copper under high temperature conditions could enhance lubricating abilities.