Study On Wear Resistance Of Laser Cladding Iron-based Self-Lubricating Coatings On H13 Steel

Fe-based alloy coating,self-lubricating coating containing LaF₃ and self-lubricating coating containing MoS₂ were prepared on the surface of H13 steel by using TruDisk6002 disc laser in synchronous side powder feeding mode.The phase structure,micro-morphology,composition and microhardness of the coating were tested and analyzed by using X-ray diffractometer?XRD?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscope?SEM?,energy spectrometer?EDS?,direct reading spectrometer and microhardness meter and other microscopic analysis methods.The friction and wear properties of H13 steel,alloy coating and self-lubricating coating were tested at room temperature by MMU-5GA vacuum high temperature friction and wear tester.The friction and wear behavior of Fe-based alloy coating and two kinds of self-lubricating coating were studied,with emphasis on the friction-reducing and wear-resisting mechanism and self-lubricating characteristics of the coating after adding self-lubricating phase.The formation and function of friction layer were analyzed and discussed,and the wear mechanisms of H13 steel,Fe-based alloy coating and self-lubricating coating were discussed.It is found that the three alloy coatings prepared by laser cladding technology not only have good quality,but also have good metallurgical bonding with the substrate.In addition,the self-lubricating coating is smoother and the crystal grains are finer.Although the hardness of the self-lubricating coating is lower than that of the base alloy coating,it is much higher than that of H13 steel.The matrix phase in Fe-based alloy coating is?-Fe,and the strengthening phase is intermetallic compound.The self-lubricating coating containing LaF₃ contains a small amount of LaF₃ and La₃BO₄self-lubricating phases,while the self-lubricating coating containing MoS₂ contains a small amount of FeS₂,TiS₂ and MoS₂.The experimental results of friction and wear show that at the same rotating speed,the wear amount of H13 steel increases sharply with the increase of load,while the wear amount of alloy coating shows a slow growth trend.When the rotating speed is 50r/min,the wear amount and friction coefficient are in descending order of H13steel>Fe-based alloy coating>LaF₃ coating>MoS₂ coating.When the rotating speed is 100r/min and the load is below 150N,the wear amount of coatings containing LaF₃ and MoS₂ is similar,of which the former is slightly lower,which is significantly lower than that of Fe alloy coating and H13 steel in turn.however,when the load increases to 200N,the wear amount of coatings containing LaF₃ suddenly increases and exceeds that of coatings containing MoS₂.After comparing the friction coefficient,it is found that the coating containing self-lubricating phase can significantly reduce the friction coefficient,and can increase the rotating speed and reduce the friction coefficient.The results show that the Fe-based alloy coating prepared by laser cladding,the self-lubricating coating containing LaF₃ and the self-lubricating coating containing MoS₂ can all improve the wear resistance and self-lubricating performance of H13 steel.Through the mechanism of friction reduction and wear resistance,it is shown that the wear surface of Fe-based alloy coating forms oxide friction layer with certain lubrication and protection effects,which reduces the friction coefficient and wear amount.The coating containing LaF₃and MoS₂ has better wear resistance and friction reduction because it forms an oxide friction layer containing self-lubricating phase.Although the increase of friction heat at high rotational speed leads to the intensified wear of H13 steel and Fe-based alloy,it is beneficial to the formation of high-quality lubricating friction layer and presents better self-lubricating characteristics.