Effect of La containing phases on microscopic wear characteristics and residual stress of WC–Co cemented carbide

During the sintering process of WC–11Co–0.71Cr3C2–0.06La2O3 cemented carbide with a WC + β + η structure, a dispersedly distributed La2O2S phase along with a LaCoO3 phase in minor amount was formed in situ on the sinter skin (surface). To analyze the microscopic wear characteristics and residual stress, as well as the related bond strength between the La2O2S phase and the WC + β matrix, both the sinter skin and the heavily ball-milled skin (surface) of the same sample were examined by a scanning electron microscope and two kinds of X-ray diffractometers. The following facts were established: (1) high bond strength between the La2O2S phase and the WC + β matrix, (2) high wear resistance of the La2O2S phase (as small as 0.25 μm/h in wear amount) and (3) a well-matched wear resistance between the La2O2S phase and the matrix. The synergetic wear of the La2O2S, LaCoO3, WC and β phases led to an approximately 28% decrease of residual stresses in the WC phase. Nevertheless, a compressive stress state still remained. Dispersedly distributed La2O2S or LaCoO3 phase on the surface can endow WC–Co cemented carbide with a self-lubricating function and a related high wear resistance performance.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A method for investigation of the wear behavior of a microscopic phase is proposed. ► La2O2S phase and WC + β matrix are well-matched in terms of wear resistance. ► There is a high bond strength between La2O2S phase and WC + β matrix. ► Synergetic wear led to ca. 28% decrease of residual compressive stresses in WC phase. ► La2O2S or LaCoO3 phase can endow WC–Co alloy with a self-lubricating function.