Research On Application Fundament Of Hard Cerment Cladding Materials

Hard cermet cladding material is a new kind of composite material manufactured by cladding cermet on the substrate with advanced coating technologies. It can be widely used in anti-corrosion, wear-resistant and high temperature, and so on. Aimed at the status quo of the relative singleness of the hard phase and lacking application of the material, in the paper, based on the preparation of the ternary boride hard clad on the steel substrate successfully, in order to optimize the hard cladding material system, the structure of single hard phase in the hard alloy cladding materials is broken through, and a novel hard cladding material with high hardness, excellent wear and corrosion resistance with more hard phase cladding materials including the ternary boride and carbide clad on the side of the steel is developed. The new type of cladding material is applied in the surface of the machine parts, and good effects are obtained.The new type of hard cladding material system is designed by the material thermodynamics and diffusion kinetic. Six types of cladding materials have been developed successfully on the steel for the first time, which is designated W series, C series, F series, CW series, TC series and WTC series respectively. The effect of the sintering ambience, temperature increasing velocity, sintering temperature and the preservation time on the properties of hard cermet cladding materials are investigated deeply and the sintering technics of hard cermet cladding materials is established.The mechanical properties such as hardness, fracture toughness, the flexural strength and the corrosion resistance of the hard cermet cladding material are investigated. The effects of carbide content and sintering temperature on the hardness are investigated in detail. The carbide which is mixed into the cladding increased the hardness prominently. The Vickers hardness of CW series and TC series both increase as accession of carbide content. The maximum of hardness is 11.77GPa and 12.53GPa separately. And then the hardness decreases as the increasing of carbide content. The effect of carbide content on cladding material flexural strength is studied. The experiment results show that the carbide content increases the flexural strength obviously whether the hard cermet cladding material bear compressive stress or draw stress bear. The wear resistance is studied by dry friction and erosion wear. It is indicated that the wear resistance of the six kinds of new type of cladding material is improved reasonably compared with that of the single phase ternary boride hard cermet cladding material.It studies the phase composition, the distribution of the hard phase and adhesive phases. The interface character between the carbide and the ternary boride and the interface character between the cladding and the substrate are both investigated. The effects of sintering parameters on the microstructure are studied. The compartmentalization of the diffuse interface between steel and cladding material is advanced. The formation mechanism of the interface is investigated by the line scan analysis. The process of "proliferation-dissolve-proliferation" makes the thickness of the liquid interface layer growing under high temperature. It forms liquid interface with a certain thickness. When the cladding material cools from high temperature, the liquid interface solidifies to the interface between the steel substrate and cladding.The matching target of hard cermet cladding materials, which limits the volume, shape and surface roughness of cladding parts, is summarized as follows: for the cladding parts, their size is limited within 400mmx400mmx600mm, their shape is relatively simple, their surface roughness is undemanding, the loading is wear load mostly, and the working temperature isn't beyond 1000℃.The empirical model of sintering temperature of the hard cermet cladding parts is estabilished. The results show that the sintering temperature of the parts relates with the of volume of it with the different series of hard cermet cladding material. The preparation, use and failure modes as well as failure mechanism are investigated in various situation such as wear condition to roller, erosion condition to abrator vane in shot blasting machine, and multiple shock loading condition to hammer in deburring machine. The results show that, first, the failure modes of hard cermet cladding parts include pitting corrosion, scratch, crack, and exfoliation of cladding; second, the failure mechanism is abrasive wear and fatigue wear mainly, as well as adhesion abrasion in wear condition, erosive failure in erosion condition and multiple shock loading failure in multiple shock loading condition. It confirms the selection principle of cladding materials according to different using requirement in different situation.Based on different failure modes and mechanism in different working condition, the lifetime model and its estimate criterion of failure for hard cermet cladding parts in both wear condition and erosion condition are drawn respectively. According to the characteristic that the status of cladding parts is of fuzziness and the failure modes are various, the model is built for fuzzy reliability and fuzzy average lifetime of reliability of hard cermet cladding parts series-wound failure system. And then the fault tree sequence of hard cermet cladding parts is established and analyzed in different condition. The results show that erosion wear lifetime of hard cermet cladding parts accorded with log-normal distribution. Fuzzy reliability is computed by lower limit membership function, and parameters of the part are estimated by the maximum likelihood approach. In the end, the fuzzy reliability of hard cermet cladding parts is confirmed.