| Die is the basic tooling in industrial-production.Die life is not only an important symbol to measure the level of a country's product manufacturing,but also the important factor of affecting product quality,machining efficiency and cost.Hot die steel is a kind of very important steel in the industry of die.There has been great economic significance to raise the service life of hot die by surface treatment technology.The cladding of Ternary boride based cermets is prepared on H13 steel substrate surface by spark plasma sintering in this paper.The microstructures of cladding and bonding pad interface,and micro-hardness distribution are observed respectively by SEM,EDS,XRD and micro hardness instrument.The abradability and thermal fatigue property of the cladding sample and H13 steel sample without cladding are compared,and the wear-resisting mechanism and thermal fatigue mechanism of the cladding are analyzed.The experiment results show that the temperature and time of sintering can be reduced highly in preparing the cladding of Ternary boride based cermets by spark plasma sintering.The degree of densification of cladding is high,and the relative density of cladding is up to 99.2%when the temperature of sintering is 1050℃,the soaking time is 5 min and the pressure of sintering is 30 MPa.There has been a large mount of Mo2FeB2 hard phase with compact structure,close grain and full grain,andα-Fe bonding phase fills in around the hard phase.The element diffusion is generated on the interface region of cladding and steel substrate.A good combination interface is formed.The cladding has high surface micro hardness.The maximal Rockwell hardness and micro hardness of cladding are up to 88.5 HRA and 1400 HV respectively,and the micro hardness of substrate is about 600 HV.So the hardness of cladding has higher hardness than substrate remarkably.No sudden change between cladding and steel substrate can be found,but a transitional layer of hardness is formed.The abradability of cladding is higher than H13 steel.The wear-resisting mechanism of cladding can be expounded by the adhesive wear and oxidative wear.The cladding has higher thermal fatigue resistance than H13 steel without cladding.The experiment results show that the coating suffers more thermal cycle times before appearing macroscopic thermal fatigue crack,and the crack width of cladding is narrower than H13 steel after 300 thermal cycles.The micro hardness of sample surface has been declined to a certain extent,and the degressive scope of micro hardness of cladding is smaller than H13 steel with no cladding after thermal cycle. |
