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Through simulation based on the Workbench platform in ANSYS the optimal laser remelting process parameters were identified to achieve the maximum performance of a Ni60 coating laser clad onto a H13 steel surface. Laser remelting with a fibre laser was conducted according to the optimal process parameters obtained and the coating morphology, microstructure and microhardness after remelting were analysed. The results show that when the laser power was 1200 W and the scanning speed was 4 mm/s the remelted coating has the smallest residual stress value, pores in the coating were basically eliminated, the organization was dense, the hardness improved and the coating quality was the best. When the laser power was 900 W and the scanning speed was 2 mm/s the maximum residual stress value of the remelted coating was slightly smaller than that of the un-remelted coating, the coating morphology quality was better, and there were very few bubbles. [ABSTRACT FROM AUTHOR]

In view of the difficulties such as coarse microstructure, performance degradation and excessive residual stress during the preparation of Ti-6Al-4V layers by laser cladding, the microstructure and mechanical properties of such a Ti-6Al-4V coating were optimized and improved based on the plastic deformation effect caused by laser shock peening (LSP). The characteristics of phase composition, changes in microstructure and morphology, grain plastic deformation and the influence of mechanical properties of the laser clad Ti-6Al-4V coating were studied pre- and post-LSP. The results indicate that the α/α' phase content increases and the β phase content decreases after LSP. The β phase and acicular martensite α' phase is refined significantly and divided, and the basket structure presents a more dense and staggered distribution after LSP. Laser cladding causes the grains in the Ti-6Al-4V coating to undergo plastic strain and the degree of grain refinement was significantly improved following LSP. The microhardness at the top of the laser clad Ti-6Al-4V coating increases from 23 to 30% compared after LSP. At the same time, the LSP promotes the transformation of residual tensile stress to compressive stress on the surface of the laser clad Ti-6Al-4V coating, with an average residual compressive stress value of about 339 MPa. This study provides theoretical and methodological references for optimizing the microstructure and properties of Ti-6Al-4V coatings. [ABSTRACT FROM AUTHOR]

WC-enhanced Ni-based coatings were prepared in situ on a H13 steel substrate by laser cladding with a fibre laser. The influence law of the central temperature per unit mass of powder, acting on the morphology, microstructure, microhardness and friction wear properties of the coating was investigated. The results show that the metallurgical bonding between the WC--enhanced Ni-based coating and base metal (BM) was good. The dilution rate of the clad layer increases with the increase of. WC, Cr3C2 reinforcing phases, FeNi3 solid solution, FeC carburized body, Fe3W3C interstitial compound are mainly present in the coating at different values of The microstructure gradually changes from dendritic and cellular to irregular aggregation with increasing. The microhardness of the coating increases first and then decreases with the increase of. The microhardness of the coating is the highest when 1=16483 K/g. A value of a=16483 K/g gave the best wear performance. The wear mechanism of the WC-enhanced Ni-based coating is mainly adhesive wear, brittle spalling and abrasive wear. [ABSTRACT FROM AUTHOR]

A Ni60/WC gradient composite coating was prepared on the surface of H13 steel by the laser cladding in situ generation method using a fibre laser. The phase composition, microstructure, microhardness and wear mechanism of the laser clad Ni60/WC gradient composite coating were analysed to reveal that it possessed few pores and cracks, the delamination phenomenon was obvious, the enhancement phase was small and uniformly distributed, and it formed a good metallurgical bond with the H13 steel substrate. In the laser clad Ni60/WC gradient composite coating the branch reinforcing phases are mainly WC, W2C, WSi2 phases, and a small amount of Cr7C3, FexC and other compounds, and the interbranch structures are mainly A-[Fe,Ni] solid solution and Cr7C3, FexC and other compounds. The Ni60+40% (W+C) and Ni60+20% (W+C) layers gradually decrease in number and size from top to bottom, while the shape gradually changes from irregular tetragonal to petal-shaped. The microhardness of the laser clad Ni60/WC gradient composite coating shows a gradient downward trend from top to bottom, and the maximum hardness can reach 1083.7 HV0.5 and the average hardness was 4.18 times that of the H13 steel substrate. The wear amount of the laser clad Ni60/WC gradient composite coating is 20.3% of the H13 steel substrate. The wear mechanism is mainly adhesive wear, brittle spalling and abrasive wear, which can prolong the service life of the mould and reduce the waste of resources. [ABSTRACT FROM AUTHOR]

Using a fibre laser, the effect law of laser cladding process parameters on the morphology quality and dilution rate of Ni60 alloy powder clad onto H13 steel was examined. Laser power, scanning speed, powder feeding voltage, clad layer width, clad layer height, meltpool depth, the ratio of width to height and the dilution rate were established by response surface methodology (RSM) though a central composite design (CCD). The correctness of the mathematical model was verified by analysis of variance (ANOVA) and test index. The results show that the width of the laser clad layer is negatively correlated with the scanning speed, and the influence of laser power and powder feeding voltage is not significant. The height of the laser clad layer is positively correlated with the powder feeding voltage and negatively correlated with the scanning speed, and the laser power has no significant effect on it. The depth of the meltpool is positively correlated with laser power and negatively correlated with scanning speed and powder feeding voltage. The aspect ratio and dilution rate are positively correlated with the laser power and scanning speed, and negatively correlated with the powder feeding voltage, and the influence of the powder feeding voltage on them is the most significant. The process parameters were optimized with the fixed range of aspect ratio and the minimum dilution rate as the objectives. Through experiments, the average errors of predicted and actual value of aspect ratio and dilution rate are 8.1 and 11.1%, respectively. The research results provide a theoretical basis for the morphology control of single laser clad coating and the optimization of process parameters. [ABSTRACT FROM AUTHOR]