Abstract
In order to improve the tribological performance of the slanted guide pillar, Cu particle reinforced composite coatings were synthesized on the surface of GCr15 steel using the plasma transferred arc (PTA) alloying technique. A systematic experimental investigation was conducted to study the effects of PTA current on the microstructure and microhardness of alloyed coatings. In addition, tribological behaviors at room temperature (RT) and high temperature (HT) were investigated. The results indicate that at low PTA current (70A), due to the insufficient current, no Cu particles are dissolved in the alloyed coating and a Cu-rich layer is observed on the surface. With the increase in the PTA current, Cu particles are gradually dissolved into the alloyed layer and the microstructure of alloyed coating mainly consists of bamboo-like martensite, retained austenite, and dispersed Cu particles. The microhardness of the PTA samples is approximately four times that of the untreated sample. The tribological results exhibit that an abrasive wear at RT and slight abrasive wear with oxidation wear at HT are the dominant wear mechanisms of alloyed coatings. The PTA samples show far superior antifriction properties compared to the untreated and remolten samples at both RT and HT, which can be attributed to the formation of lubricating Cu films and the improvement in microhardness.
Highlights
As the guide device of the core-pulling mechanism in the injection mold, the performance of the slanted guide pillar has an important influence on the smooth opening and closing of the injection mold.GCr15 steel is an attractive material for the slanted guide pillar because of its high fatigue resistance and good dimensional stability [1]
At an arc current of 70 A, the molten pool morphology of sample 1 was separated into two regions: the heat affected zone (HAZ), and the substrate zone (SZ). This is the result of there being insufficient energy for the sample to melt the copper into the substrate pool to form an alloyed zone
As the arc current increases (90 A, 110 A), it can be clearly seen from Figure 2b,c that the cross-section layers of samples 2 and 3 are divided into three moon-like regions: the alloyed zone (AZ), the heat affected zone (HAZ), and the substrate zone (SZ)
Summary
As the guide device of the core-pulling mechanism in the injection mold, the performance of the slanted guide pillar has an important influence on the smooth opening and closing of the injection mold. Bourithis et al [11] focused on producing a metal matrix composite tool steel with TiC as reinforcing particles using PTA technology and investigated the wear behavior under different sliding speeds. Cao et al [13] found that synthesizing a high-vanadium high-speed steal alloying layer on nodular cast iron could increase the hardness and improve wear resistance This may not be an effective method for producing a composite layer with hard phases for materials with a high load and high frequency of use, such as slanted guide pillars. Zeng et al [18] synthesized a composite coating of Cu on high nickel austenitic ductile iron using laser surface alloying under two different processing conditions They studied the evolution of the microstructure, distribution of the alloying elements, and hardness of the alloyed zone. An untreated GCr15 sample and a remolten sample without copper addition were used for comparison purposes
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