Research on the inwall shot blasting of the S30432 high-pressure boiler tube

Inwall shot blasting is a method of improving the surface hardness and high temperature oxidation resistance of the S30432 high-pressure boiler tube.The differences on residual stress,sub-grain size,micro-hardness and structure between the S30432 inwall shot-blasting tube produced by Baosteel with six technological process parameters and the imported super 304H were studied systematically by contrast test research.It has been demonstrated that the S30432 obtains a higher residual stress,a deeper distributed layer and a better sub-grain size of the inwall field shot-blasting layer;the martensite content of the shot-blasting surface was low;and micro-hardness and structure refinement were better.After 2000 h’ oxidation test under the 650℃/26MPa steam condition,steam oxidation resistance of the Baosteel steel tube shot-blasting surface was higher,the oxide layer was thinner,and was well combined with bulk material.

Friction Behavior of Laser Beam Texture Sheets and Shot Blast Sheets

The friction behaviors of steel sheets at the corners of die and punch, under different conditions of surface textures (laser beam texture, shot blast texture), steel sheet rolling directions and lubricants, are studied by both SEM micro surface observations and friction coefficients measurement. The results show the friction coefficient at the corner of die is smaller than that at the corner of punch during stamping. The friction coefficient along rolling direction is lower than that along transverse direction, especially at the corner of punch. Differential initial surface texture has different sensitivity of friction coefficient to the lubricants. The sheet surface with laser beam texture (LBT) has shown a stronger adaptation to various lubricants than that with shot blast texture (SBT). After stamping, the surface with laser beam texture is still clear, the shot blast texture is indistinct.

Effect of surface treatment to inserted ring on Al–Fe bonding layer of aluminium piston with reinforced cast iron ring

In order to improve the bonding strength between piston alloys and cast iron ring of aluminum piston with reinforced cast iron ring,the different methods of the surface treatments(shot blasting and sand blasting) to the cast iron ring are experimented.The optical micrograph shows that an intermetallic layer and a ligulate shaped structure are formed between piston alloys and cast iron base ring.After sand blasting treatment,the ring surface is non-metal shiny,matte-like and has no obvious pits.The intermetallic layer thickness formed between piston alloys and cast iron is thinner and more equally distributed after sand blasting to the ring.The content of the graphite distributed the interfacial zone after the shot blasting treatment is little.With the increase of time by sand blasting,the hardness starts to slightly descend.The bonding strength of the sample by sand blasting is obviously higher than that by shot blasting and increases from 9.32 MPa to 19.53 MPa.

Enhanced mechanical performance of gradient-structured CoCrFeMnNi high-entropy alloys induced by industrial shot-blasting

In this study,CoCrFeMnNi high-entropy alloys(HEAs)with a surface gradient nanostructure were produced using industrial shot blasting,which improved their mechanical properties compared to the untreated alloy.The severely plastically deformed(SPD)surface layer had a multi-scale hierarchical structure with a high density of stacking faults,deformation nanotwins,and amorphous domains.The depth of the SPD layer steadily increased as the shot-blasting time increased.The differences in the microhardness and tensile strength before and after shotblasting demonstrated the significant effect of the SPD layer on the mechanical performance.The microhardness of the homogenized HEA was~5 GPa.In comparison,the maximum microhardness of the specimens after 20 min of shot blasting was~8.0 GPa at the surface.The yield strength also improved by 178%,and a large ductility of~36%was retained.Additional nanograin boundary,stacking fault,and twin strengthening within the gradientnanostructured surface layer caused the strength to increase.During tensile deformation,strain concentration began at the surface of the specimen and gradually spread to the interior.Thus,the gradient-nanostructured surface layer with improved strain hardening can prevent early necking and ensure steady plastic deformation so that high toughness is achieved.