بررسي خواص سايشي كامپوزيت برنج ـ گرافيت

Wear Properties of Brass-Graphite Composite

در اين مقاله، اثر گرافيت بر خواص سايشي آلياژ برنج C86300 بررسي شده است. سازوكار آزمون سايش يا به‌كارگيري دستگاه سايش پين روي ديسك در شرايط خشك و سرعت خطي 0/5 ميلي‌متر بر ثانيه با نيروي اعمالي 14 كيلوپاسكال و مدت زمان 30 ثانيه بررسي شد. شرايط ياد شده براي نمونه‌هاي كامپوزيتي و شاهد استفاده شد. نمونه‌ي كامپوزيتي با استفاده از روش فشرده‌سازي پودر گرافيت، مس و روي و سپس زينتر كردن آن در دماي 500 درجه‌ي سانتي‌گراد در محيط خلا و سپس افزودن به مذاب برنج تهيه شد. در اين تحقيق كامپوزيت‌هاي برنج ـ گرافيت شامل 15ـ4/8 درصد وزني گرافيت با روكش نيكل توليد مي‌شوند. خواص تريبولوژيكي سطحي اين ماده در محيط آب دريا بررسي شد كه در نتيجه‌ي آن ضريب اصطكاكي كامپوزيت‌ها با افزايش حجم گرافيت كاهش يافت. مقاومت سايشي با اضافه كردن گرافيت با روكش نيكل بهبود يافت، اما به ازاي حجم بيشتر گرافيت كاهش پيدا كرد. كامپوزيت با 7/11 درصد وزني گرافيت با نيكل روكش شده بهترين خواص تريبولوژيكي را نشان داد.

In this paper, the effect of graphite on the wear properties of C86300 brass alloy has been investigated. Mechanism of wear test was studied by pin on disc wearing machine in dry conditions, and the linear speed of 0.5 mm/s, force with 14kPa and time of 30 seconds. Brass-graphite compo site was fabricated by adding Graphite/Cu/Zn compact powder under stir casting technique and its tribological behaviors against the brass disk were studied under the simulated actual conditions, in comparison with the common graphite/Brass composite. In this study, brass-graphite composites containing 8.4-15 wt. % of Ni-coated graphite were fabricated. The tribological properties were investigated under sea water condition. The friction coefficient of composites decreased with increasing graphite content. The wear resistance was improved by the addition of Ni-coated graphite but degraded at high graphite content. The results indicated this composite showed much better mechanical properties and tribological properties in comparison with Brass. The composite with 11.7 wt. % nickel coated graphite showed the best tribological properties. The wear mechanism of the composite is abrasive wear and plastic deformation in sea water environment. The wear mechanism of uncoated graphite composite is plough and delamination wear. The wear mechanism of nickel coated graphite composites is micro-plough and delamination wear. The corrosion of sea water increases the specific wear rate but shows a lubricating effect during the sliding process.