Quality assessment of laser cladded HSS coatings with deep penetration into base material to obtain a smooth gradient of properties in coating-substrate interface

摘要

The present research is dedicated to the study of influence of coaxial laser cladding (CLC) process parameters onto values of alloying components content in the coatings, morphology as well as the influence of post-cladding heat treatment on the quality and mechanical properties of coatings. The research is based on a hypothesis that applying of first layer of coatings onto steel substrate with keyhole in penetration allows achieving smooth gradient of properties of the coating-substrate system. As a result it may provide a smooth distribution of the internal residual stresses in interface as well as the better resistance to external stress during cyclic load in tool operation processes: metal forming, stamping etc. Experimental work was carried out using CLC system, which consists of industrial robot Kuka and 1 kW IPG Yb-fiber laser, integrated to the coaxial powder supplying cladding head. The regularities of formation of High Speed Steel AISI М2 cladding coatings created by different regimes were studied by deposition onto EN 41Cr4 and C80U steel substrates. The quality of achieved coatings has been evaluated by examination of morphology of transverse cross-sections, coatings geometrical features, elemental composition and microhardness distribution inside coatings. Additionally detailed assessment of coating thickness and content of alloying elements using statistical methods has been performed. As a result of the research done the degree of influence of chosen CLC process parameters onto quality characteristics were estimated. The most appropriate cladding regime for used method was proposed.