Study On Process,Microstructure And Wear Properties Of Laser Cladding Alloy On H13 Steel

H13 steel(4Cr5MoSiV1)as the most common hot work die steel,is widely used as hot forging dies,hot extrusion dies,etc.which is required to work for long time under the harsh conditions,such as high temperature and load.High-temperature wear is one of main failure patterns.Preparing a high wear-resistant coating on the surface of H13 by laser cladding technology would be an effective method to overcome this issue.In this study,Ni-Cr-Mo alloy coating was obtained by laser cladding of high-nickel-iron alloy powders on H13 steel.The influence of laser cladding parameters on coating quality was studied and the optimal parameters were achieved.The high temperature wear properties tests of the coating and H13 steel were performed by a friction and wear tester.The microstructure,morphology,phase and composition of the coating and worn surfaces were observed and analyzed by SEM,X-ray diffractometer and EDS spectrometer.Besides,the wear mechanism was also explored.Clearly,this research presented the important theoretical significance and potential industrial application value.The results showed that the laser process parameters had a significant influence on the quality of the laser cladding layer.The optimal laser process parameters as followed: 0.5mm for the thickness of the coating,300 A for the laser current,2mm/s for the laser scanning speed,2ms for the laser pulse width,20 Hz for the laser frequency.The obtained cladding layer presented excellent forming quality,fine structure,no voids and crack as well as a good metallurgical bond with the substrate.From the upper portion of the coating to the bottom,the structure of the cladding layer transformed from a uniform equiaxed crystal into a long dendritic one.The phase of the cladding coating mainly included ?-(Fe,Ni);as matrix and the intermetallic compound dispersed as a strengthening phase.The maximum hardness of the cladding coating was up to 875.1HV.The friction and wear tests showed that the wear loss of laser cladding alloy coating was much lower than that of H13 steel.Especially under the condition of 600 °C and 150 N,the laser cladding alloy coating had an excellent wear resistance with about 1/5 wear loss of H13 steel.The wear mechanism of the laser cladding alloy coating at 400-600 °C was mainly oxidative mild wear,accompanied by abrasive wear.The wear mechanism of H13 steel was the same as laser cladding alloy coating.However,under the high temperature and load(600°C,150N),the plastic extrusion wear,severe wear prevailed because of low thermal stability and thermal strength of H13 steel.The high thermal stability and strength of the laser cladding alloy coating supported oxide-containing friction layers,thus ensuring oxidation mild wear even under high temperatures and high loads.